View source for Blood alcohol content

{{Short description|Metric of alcohol intoxication}}
{{use dmy dates |date=March 2022}}
{{Infobox diagnostic
| name = Blood alcohol content
| synonyms = Blood alcohol concentration, blood ethanol concentration, blood alcohol level, blood alcohol
| image = Ethanol-3D-balls.png
| alt =
| caption = [[Ethanol]]
| DiseasesDB = 
| ICD10 = 
| ICD9 = 
| ICDO = 
| MedlinePlus = 
| eMedicine = 
| MeshID = 
| LOINC = {{LOINC|5639-0}}, {{LOINC|5640-8}}, {{LOINC|15120-9}}, {{LOINC|56478-1}}
| HCPCSlevel2 = 
| reference_range = 
}}

'''Blood alcohol content''' ('''BAC'''), also called '''blood alcohol concentration''' or '''blood alcohol level''', is a measurement of [[alcohol intoxication]] used for legal or medical purposes.<ref name="Med2019">{{cite web |date=3 December 2020 |title=Blood Alcohol Level |url=https://medlineplus.gov/lab-tests/blood-alcohol-level/ |website=MedlinePlus |publisher=National Library of Medicine |language=en}}</ref> 

BAC is expressed as mass of [[alcohol (drug)|alcohol]] per volume of blood. In US and many international publications, BAC levels are written as a percentage such as 0.08%, i.e. there is 0.8 grams of alcohol per liter of blood.<ref name="Med2019" /><ref name="BAC"/> In different countries, the [[Drunk driving law by country|maximum permitted BAC when driving]] ranges from the [[limit of detection]] ([[zero tolerance]]) to 0.08% (0.8 {{abbr|g/L|grams per liter}}).<ref>{{cite news |title=Drink-drivers in Nepal face the 'smell test' crackdown |url=https://sg.news.yahoo.com/drink-drivers-nepal-face-smell-test-crackdown-034220138.html |work=Yahoo News |date=22 July 2012 |language=en-SG}}</ref><ref name="BAC">{{cite web|url=http://apps.who.int/gho/data/view.main.54600|title =Legal BAC limits by country|publisher =[[World Health Organization]]|access-date =12 November 2023|ref =none}}</ref> BAC levels above 0.40% (4 g/L) can be potentially fatal.<ref name="Med2019" />

According to [[Guinness World Records]], 1.374% (13.74 g/L) is the highest BAC ever recorded in a human who survived the ordeal.<ref name=":2">{{Cite web |title=Highest blood alcohol level |url=https://www.guinnessworldrecords.com/world-records/118837-highest-blood-alcohol-level |url-status=live |archive-url=https://web.archive.org/web/20241207045311/https://www.guinnessworldrecords.com/world-records/118837-highest-blood-alcohol-level |archive-date=7 December 2024 |access-date=2024-12-06 |website=[[Guinness World Records]]}}</ref> The record was set in July 2013 by an unidentified Polish man found unconscious by the side of a road in the village of [[Tarnowska Wola, Subcarpathian Voivodeship|Tarnowska Wola]], in south-east [[Poland]]. First responders reportedly did not believe the initial BAC readings taken at the scene, possibly due to it being almost 69 times greater than the [[Drunk driving law by country#Europe|Polish legal limit of 0.02%]] (0.2 g/L). However, the reading was later confirmed after the man was transported to a nearby hospital.<ref name=":2" />

== Units of measurement ==

BAC is generally defined as a fraction of weight of alcohol per volume of blood, with an [[SI coherent derived unit]] of [[Kilogram per cubic metre|kg/m<sup>3</sup>]] or equivalently grams per liter (g/L). Countries differ in how this quantity is normally expressed. Common formats are listed in the table below. For example, the US and many international publications present BAC as a percentage, such as 0.05%. This would be interpreted as 0.05 grams per deciliter of blood. This same concentration could be expressed as 0.5‰ or 50&nbsp;mg% in other countries.<ref>{{cite web |title=BAC Formats |url=http://www.mecinca.net/ALCOHOLIMETROS_Alcosim/BAC%20BrAC%20conversion%20table[1].pdf |access-date=3 November 2023}}</ref>

{| class="wikitable" style="margin: 1em auto 1em auto"
! Sign !! Units !! Used in
|-
| 1 percent (%), 1 g%<ref name="Jones2011" /> || {{val|1|u=g/dL}} = {{val|1|u=cg/mL}} = {{val|10|u=g/L}} = 1 g/100 mL || US, Australia,<ref name="Jones2011" /><ref>{{Cite web |date=8 February 2022 |orig-date=Original date 14 February 2017 |title=Blood alcohol levels |url=https://adf.org.au/insights/blood-alcohol-levels/ |website=Alcohol and Drug Foundation (Australia)}}</ref> Canada<ref>{{Cite web |date=n.d. |title=Blood Alcohol Concentration (BAC) |url=https://madd.ca/pages/impaired-driving/overview/blood-alcohol-concentration-bac/ |access-date=21 July 2022 |website=Mothers Against Drunk Driving (MADD Canada)}}</ref>
|-
| 1 [[per mille]] (‰){{efn|In Germany, Finland, Netherlands and Sweden, the local language term ''[[per mille|promille]]'' is used; this is occasionally provided as a courtesy in English texts.<ref name="HRB BAL">{{cite web |title=Blood alcohol level (BAL) |publisher=Health Research Board (Ireland) |url=https://www.drugsandalcohol.ie/glossary/info/blood_alcohol_level }}</ref>}}   || {{val|1|u=g/L}} = {{val|1|u=mg/mL}} = 100 mg/1 dL || Austria,<ref name="Jones2011" /> Belgium,<ref name="Jones2011" /> Bulgaria,{{cn|date=November 2023}} Czech Republic,{{cn|date=November 2023}} Denmark,{{cn|date=November 2023}} France,<ref name="Jones2011" /> Germany,<ref name="Jones2011" /> Latvia,{{cn|date=November 2023}} Lithuania,{{cn|date=November 2023}} Netherlands,<ref>{{Cite web|url=http://wetten.overheid.nl/jci1.3:c:BWBR0006622&hoofdstuk=II&paragraaf=1&artikel=8&lid=2|title=artikel 8, tweede lid, van de Wegenverkeerswet 1994|date=21 February 2025}}</ref><ref>{{Cite web|url=https://www.rijksoverheid.nl/onderwerpen/verkeersveiligheid/vraag-en-antwoord/mag-ik-met-alcohol-op-deelnemen-aan-het-verkeer|title=Met hoeveel alcohol mag ik deelnemen aan het verkeer?|date=21 February 2025}}</ref> Poland,<ref>{{Cite journal |date=2019-10-15 |title=Nietrzeźwość a ryzyko zgonu w wypadku komunikacyjnym = Insobriety and the risk of death in traffic accident {{!}} Journal of Education, Health and Sport |url=https://apcz.umk.pl/JEHS/article/view/2761 |journal=Journal of Education, Health and Sport | volume=5 | issue=6 | pages=419–432 |language=pl | last1=Lasota | first1=Dorota | last2=Staniszewska | first2=Anna | last3=Tarchalska-Kryńska | first3=Bożena | last4=Mirowska-Guzel | first4=Dagmara | last5=Krajewski | first5=Paweł }}</ref> Portugal,{{cn|date=November 2023}} Romania,{{cn|date=November 2023}} Russia,{{cn|date=November 2023}} Slovenia,{{cn|date=November 2023}} Spain,<ref name="Jones2011" /> Sweden,{{cn|date=November 2023}} Switzerland,{{cn|date=November 2023}} Turkey{{cn|date=November 2023}}
|-
| 1 [[Milligram per cent|mg%]]<ref name="Jones2011" /> || {{val|1|u=mg/dL}} = {{val|0.01|u=g/L}} = 1 mg/100 mL || United Kingdom<ref>{{cite web |title=The drink drive limit |url=https://www.gov.uk/drink-drive-limit |access-date=3 November 2023 |website=GOV.UK |language=en}}</ref> Ireland, Canada, New Zealand<ref name="Jones2011" />
|}

It is also possible to use other units. For example, in the 1930s Widmark measured alcohol and blood by mass, and thus reported his concentrations in units of g/kg or mg/g, weight alcohol per weight blood. Blood is denser than water and 1 mL of blood has a mass of approximately 1.055 grams, thus a mass-volume BAC of 1 g/L corresponds to a mass-mass BAC of 0.948 mg/g. Sweden, Denmark, Norway, Finland, Germany, and Switzerland use mass-mass concentrations in their laws,<ref name="Jones2011" /> but this distinction is often skipped over in public materials,<ref>{{cite web |title=Drink-driving: What are the rules? |url=https://www.ch.ch/en/vehicles-and-traffic/how-to-behave-in-road-traffic/traffic-regulations/alcohol-in-road-traffic-and-navigation/#how-much-wine-or-beer-can-i-drink |website=www.ch.ch |language=en}}</ref> implicitly assuming that 1 L of blood weighs 1 kg.<ref>{{cite news |last1=Nager |first1=Anna |title=Alkoholpromille, beräkning|trans-title=Calculation of alcohol per mille |url=https://www.netdoktor.se/psykiatri/missbruk-beroende/sjukdomar/alkoholpromille-berakning/ |access-date=13 April 2024 |work=Netdoktor |date=4 May 2020 |language=sv-SE|quote=I detta sammanhang räknar man med att 1 liter blod väger 1 kilo.|trans-quote=In this context, it is assumed that 1 liter of blood weighs 1 kilogram.}}</ref>

In [[pharmacokinetics]], it is common to use the [[amount of substance]], in [[Mole (unit)|mole]]s, to quantify the dose. As the [[molar mass]] of ethanol is 46.07 g/mol, a BAC of 1 g/L is 21.706 mmol/L (21.706 mM).<ref>{{cite web |title=Ethanol |url=https://pubchem.ncbi.nlm.nih.gov/compound/Ethanol |access-date=3 November 2023 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref>

== Effects by alcohol level ==
{{Further|Short-term effects of alcohol consumption}}
{| class="wikitable"
|-
!colspan=3" | Alcohol level
!rowspan="2" | Effects
!rowspan="2" | Ref
|-
!BAC (%)
!per mille (‰)
!mg (%)
|-
|0.01 – 0.05
|0.1 – 0.5
|10 – 50
|Mild relaxation and reduced [[social inhibition]]; impaired judgment and coordination
|<ref name="cdc.gov" />
|-
|0.06 – 0.2
|0.6 – 2
|60 – 200
|Emotional swings, impaired vision, hearing, speech, and [[motor skill]]s
|<ref name="cdc.gov" />
|-
|0.2 – 0.3
|2 – 3
|200 – 300
|[[Urinary incontinence]], [[vomiting]], and symptoms of [[alcohol intoxication]]
|<ref name=":0">{{Citation |last=Dasgupta |first=Amitava |title=Alcohol, Drugs, Genes and the Clinical Laboratory: An Overview for Healthcare and Safety Professionals |date=2017-01-01 |work= |pages=1–21 |editor-last=Dasgupta |editor-first=Amitava |url=https://www.sciencedirect.com/science/article/pii/B9780128054550000014 |access-date=2023-05-24 |chapter=Alcohol a double-edged sword: Health benefits with moderate consumption but a health hazard with excess alcohol intake |publisher=Academic Press |language=en |doi=10.1016/b978-0-12-805455-0.00001-4 |isbn=978-0-12-805455-0}}</ref><ref name=":1">{{Citation |last1=Haghparast |first1=Parna |title=Alcoholic beverages and health effects |date=2022-01-01 |work=Reference Module in Biomedical Sciences |url=https://www.sciencedirect.com/science/article/pii/B978012824315200244X |access-date=2023-05-24 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-824315-2.00244-x |isbn=978-0-12-801238-3 |last2=Tchalikian |first2=Tina N.}}</ref>
|-
|0.3 – 0.4
|3 – 4
|300 – 400
|Potential total loss of consciousness; signs of severe alcohol intoxication
|<ref name=":0" /><ref name=":1" />
|-
|> 0.4
|> 4
|> 400
|Potentially fatal, may result in a [[coma]] or [[respiratory failure]]
|<ref name=":0" />'''<ref name=":1" />'''
|}
The magnitude of sensory impairment may vary in people of differing weights.<ref>{{Cite journal |last1=Dunn |first1=Richard A. |last2=Tefft |first2=Nathan W. |date=2014 |title=Has Increased Body Weight Made Driving Safer? |journal=Health Economics |language=en |volume=23 |issue=11 |pages=1374–1389 |doi=10.1002/hec.2991 |pmc=4135023 |pmid=24038409}}</ref> The [[National Institute on Alcohol Abuse and Alcoholism|NIAAA]] defines the term "[[binge drinking]]" as a pattern of drinking that brings a person's blood alcohol concentration (BAC) to 0.08 grams percent or above.<ref name="cdc.gov">"Quick Stats: Binge Drinking." The Centers for Disease Control and Prevention. April 2008.[https://www.cdc.gov/alcohol/quickstats/binge_drinking.htm].</ref>

== Estimation ==
=== Direct measurement ===
Blood samples for BAC analysis are typically obtained by taking a venous blood sample from the arm. A variety of methods exist for determining blood-alcohol concentration in a blood sample.<ref name="Dubowski">{{cite journal |last1=Dubowski |first1=Kurt M. |title=Alcohol Determination in the Clinical Laboratory |journal=American Journal of Clinical Pathology |date=1 November 1980 |volume=74 |issue=5 |pages=747–750 |doi=10.1093/ajcp/74.5.747 |pmid=7446484 |url=https://www.researchgate.net/publication/15751585}}</ref> Forensic laboratories typically use [[Headspace gas chromatography for dissolved gas measurement|headspace-gas chromatography]] combined with mass spectrometry or flame ionization detection,<ref>{{cite journal |last1=Zamengo |first1=Luca |last2=Tedeschi |first2=Gianpaola |last3=Frison |first3=Giampietro |last4=Griffoni |first4=Carlo |last5=Ponzin |first5=Diego |last6=Jones |first6=Alan Wayne |title=Inter-laboratory proficiency results of blood alcohol determinations at clinical and forensic laboratories in Italy |journal=Forensic Science International |date=1 February 2019 |volume=295 |pages=213–218 |doi=10.1016/j.forsciint.2018.12.018 |pmid=30611561 |s2cid=58591654 |issn=0379-0738}}</ref> as this method is accurate and efficient.<ref name="Dubowski"/> Hospitals typically use [[enzyme multiplied immunoassay technique|enzyme multiplied immunoassay]], which measures the co-enzyme [[NADH]]. This method is more subject to error but may be performed rapidly in parallel with other blood sample measurements.<ref>{{cite web |title=Hospital Blood Alcohol Lab Results: Are They Forensically Reliable? |url=https://www.new-jersey-dui-defense.com/hospital-blood-alcohol-lab-results-are-they-forensically-reliable.aspx |website=Law Offices of Christopher L. Baxter |date=30 April 2020}}</ref>

In Germany, BAC is determined by measuring the serum level and then converting to whole blood by dividing by the factor 1.236. This calculation underestimates BAC by 4% to 10% compared to other methods.<ref>{{cite journal |last1=Jones |first1=Alan Wayne |title=Concentration units used to report blood- and breath-alcohol concentration for legal purposes differ between countries which is important to consider when blood/breath ratios of alcohol are compared and contrasted |journal=Journal of Forensic Sciences |date=22 March 2024 |volume=69 |issue=4 |pages=1473–1480 |doi=10.1111/1556-4029.15511|pmid=38520069 }}</ref>

=== By breathalyzer ===
[[File:Breathalyser 'pint' glass - 2023-03-27 - Andy Mabbett.jpg|thumb|upright|Joke "Breathalyser 'pint{{'"}} beer glass, about 2 inches tall, dating from around the time of the introduction of [[breathalyzer]]s in the United Kingdom, in 1967]]
{{Main|Breathalyzer}}
The amount of alcohol on the breath can be measured, without requiring drawing blood, by blowing into a [[breathalyzer]], resulting in a breath alcohol content (BrAC). The BrAC specifically correlates with the concentration of alcohol in arterial blood, satisfying the equation {{math|1=BAC<sub>arterial</sub> = BrAC × 2251 ± 46}}. Its correlation with the standard BAC found by drawing venous blood is less strong.<ref>{{cite journal |last1=Lindberg |first1=L. |last2=Brauer |first2=S. |last3=Wollmer |first3=P. |last4=Goldberg |first4=L. |last5=Jones |first5=A.W. |last6=Olsson |first6=S.G. |title=Breath alcohol concentration determined with a new analyzer using free exhalation predicts almost precisely the arterial blood alcohol concentration |journal=Forensic Science International |date=May 2007 |volume=168 |issue=2–3 |pages=200–207 |doi=10.1016/j.forsciint.2006.07.018|pmid=16978819 }}</ref> Jurisdictions vary in the statutory conversion factor from BrAC to BAC, from 2000 to 2400. Many factors may affect the accuracy of a breathalyzer test,<ref>{{cite journal |last1=Jones |first1=AW |last2=Cowan |first2=JM |title=Reflections on variability in the blood-breath ratio of ethanol and its importance when evidential breath-alcohol instruments are used in law enforcement. |journal=Forensic Sciences Research |date=3 August 2020 |volume=5 |issue=4 |pages=300–308 |doi=10.1080/20961790.2020.1780720 |pmid=33457048|pmc=7782040 |doi-access=free }}</ref> but they are the most common method for measuring alcohol concentrations in most jurisdictions.<ref>{{cite journal |last1=Williams |first1=Paul M. |title=Current defence strategies in some contested drink-drive prosecutions: Is it now time for some additional statutory assumptions? |journal=Forensic Science International |date=1 December 2018 |volume=293 |pages=e5–e9 |doi=10.1016/j.forsciint.2018.09.030|pmid=30342920 |doi-access=free }}</ref>

=== By intake ===
{{Main|Pharmacology of ethanol#Modeling}}
Blood alcohol content can be quickly estimated by a model developed by Swedish professor Erik Widmark in the 1920s.<ref name=Ed>{{cite web |last1=Ed Kuwatch |title=Fast Eddie's 8/10 Method of Hand Calculating Blood Alcohol Concentration: A Simple Method For Using Widmark's Formula |url=http://www.dui-law.com/810art.htm|archive-url=https://web.archive.org/web/20031202155933/http://www.dui-law.com/810art.htm |archive-date=2003-12-02 }}</ref> The model corresponds to a [[pharmacokinetic]] single-compartment model with instantaneous absorption and [[zero-order kinetics]] for elimination. The model is most accurate when used to estimate BAC a few hours after drinking a single dose of alcohol in a fasted state, and can be within 20% [[Coefficient of variation|CV]] of the true value.<ref>{{cite conference |last1=Zuba |first1=Dariusz |last2=Piekoszewski |first2=Wojciech |title=Uncertainty in Theoretical Calculations of Alcohol Concentration |book-title=Proc. 17th Internat. Conf. on Alcohol, Drugs and Traffic Safety |date=2004 |url=https://www.researchgate.net/publication/255499090}}</ref><ref>{{cite journal |last1=Gullberg |first1=Rod G. |title=Estimating the uncertainty associated with Widmark's equation as commonly applied in forensic toxicology |journal=Forensic Science International |date=October 2007 |volume=172 |issue=1 |pages=33–39 |doi=10.1016/j.forsciint.2006.11.010 |pmid=17210238}}</ref> It is not at all realistic for the absorption phase, and is not accurate for BAC levels below 0.2 g/L (alcohol is not eliminated as quickly as predicted) and consumption with food (overestimating the peak BAC and time to return to zero).<ref>{{cite journal |last1=Searle |first1=John |title=Alcohol calculations and their uncertainty |journal=Medicine, Science and the Law |date=January 2015 |volume=55 |issue=1 |pages=58–64 |doi=10.1177/0025802414524385 |pmid=24644224|pmc=4361698 }}</ref><ref name="Jones2011">{{cite journal |last1=Jones |first1=AW |title=Pharmacokinetics of Ethanol - Issues of Forensic Importance. |journal=Forensic Science Review |date=July 2011 |volume=23 |issue=2 |pages=91–136 |pmid=26231237 |url=https://www.researchgate.net/publication/280602837}}</ref> The equation varies depending on the units and approximations used, but in its simplest form is given by:<ref>{{cite journal |last1=Maskell |first1=Peter D. |last2=Jones |first2=A. Wayne |last3=Heymsfield |first3=Steven B. |last4=Shapses |first4=Sue |last5=Johnston |first5=Atholl |title=Total body water is the preferred method to use in forensic blood-alcohol calculations rather than ethanol's volume of distribution |journal=Forensic Science International |date=November 2020 |volume=316 |pages=110532 |doi=10.1016/j.forsciint.2020.110532|pmid=33099270 |s2cid=224966411 }}</ref>
:<math>EBAC = \frac{A}{V_d}-\beta\times T</math>
where:
*{{mvar|EBAC}} is the estimated blood alcohol concentration (in g/L)
*{{mvar|A}} is the mass of alcohol consumed (g).
*{{mvar|T}} is the amount of time during which alcohol was present in the blood (usually time since consumption began), in hours.
*{{mvar|β}} is the rate at which alcohol is [[Elimination (pharmacology)|eliminated]], averaging around 0.15 g/L/hr.<ref>{{cite journal |last1=Jones |first1=Alan Wayne |title=Evidence-based survey of the elimination rates of ethanol from blood with applications in forensic casework |journal=Forensic Science International |date=July 2010 |volume=200 |issue=1–3 |pages=1–20 |doi=10.1016/j.forsciint.2010.02.021|pmid=20304569 }}</ref>
*{{mvar|V<sub>d</sub>}} is the [[volume of distribution]] (L); typically body weight (kg) multiplied by 0.71 L/kg for men and 0.58 L/kg for women<ref name="MaskellVd">{{cite journal |last1=Maskell |first1=Peter D. |last2=Heymsfield |first2=Steven B. |last3=Shapses |first3=Sue |last4=Limoges |first4=Jennifer F. |title=Population ranges for the volume of distribution ( V_d ) of alcohol for use in forensic alcohol calculations |journal=Journal of Forensic Sciences |date=September 2023 |volume=68 |issue=5 |pages=1843–1845 |doi=10.1111/1556-4029.15317|pmid=37345356 |doi-access=free }}</ref><ref name="MaskellMass">{{cite journal |last1=Maskell |first1=Peter D. |last2=Cooper |first2=Gail A. A. |title=The Contribution of Body Mass and Volume of Distribution to the Estimated Uncertainty Associated with the Widmark Equation |journal=Journal of Forensic Sciences |date=September 2020 |volume=65 |issue=5 |pages=1676–1684 |doi=10.1111/1556-4029.14447|pmid=32421216 |s2cid=218677989 }}</ref> although estimation using TBW is more accurate.<ref>{{cite journal |last1=Maskell |first1=Peter D. |last2=Jones |first2=A. Wayne |last3=Heymsfield |first3=Steven B. |last4=Shapses |first4=Sue |last5=Johnston |first5=Atholl |title=Total body water is the preferred method to use in forensic blood-alcohol calculations rather than ethanol's volume of distribution |journal=Forensic Science International |date=November 2020 |volume=316 |pages=110532 |doi=10.1016/j.forsciint.2020.110532|pmid=33099270 |s2cid=224966411 }}</ref>

A standard drink, defined by the WHO as 10 grams of pure alcohol,<ref name="WHO_AUDIT_EN">{{Cite web|url=https://apps.who.int/iris/bitstream/handle/10665/67205/WHO_MSD_MSB_01.6a.pdf?sequence=1&isAllowed=y|title=AUDIT The Alcohol Use Disorders Identification Test (Second Edition)|date=2001|website=WHO|format=pdf|access-date=2020-01-02}}</ref> is the [[Standard_drink#Definitions_in_various_countries|most frequently used measure in many countries]]. Examples:
* A 80&nbsp;kg man drinks 20 grams ethanol. After one hour:
<math display="block"> EBAC = 20/(0.71 \cdot 80) - (0.148 \cdot 1) \approx 0.204 \text{g/L} = 0.0204% \text{BAC}</math>
* A 70&nbsp;kg woman drinks 10 grams ethanol. After one hour:
<math display="block"> EBAC = 10/(0.58 \cdot 70) - (0.156 \cdot 1) \approx 0.090 \text{g/L} = 0.0090% \text{BAC}</math>

In terms of [[fluid ounce]]s of alcohol consumed and weight in pounds, Widmark's formula can be simply approximated as<ref name=Ed/>
:<math>EBAC=8\times\text{fl oz}/\text{weight in pounds}-\beta\times T</math>
for a man or
:<math>EBAC=10\times\text{fl oz}/\text{weight in pounds}-\beta\times T</math>
for a woman, where EBAC and {{mvar|β}} factors are given as g/dL (% BAC), such as a {{mvar|β}} factor of 0.015% BAC per hour.<ref name=Ed/>

===By standard drinks===
{{Main|Standard drink}}
[[File:NIH standard drink comparison.jpg|thumb|400x400px|United States standard drinks of [[beer]], [[malt liquor]], [[wine]], and [[Distilled beverage|spirits]] compared. Each contains about 14 grams or 17.7 mL of ethanol.]]
The examples above define a standard drink as 0.6 [[fluid ounces]] (14 g or 17.7 mL) of ethanol, whereas other definitions exist, for example 10 grams of ethanol.

{| class="wikitable sortable" style="text-align: center"
|+ Approximate blood alcohol percentage (by volume)<ref>[http://www.alcohol.vt.edu/Students/alcoholEffects/estimatingBAC/index.htm BAC Charts] {{webarchive |url=https://web.archive.org/web/20070630210916/http://www.alcohol.vt.edu/Students/alcoholEffects/estimatingBAC/index.htm |date=June 30, 2007 }} from [[Virginia Polytechnic Institute and State University|Virginia Tech]]</ref><br /><small>Based on one drink having {{convert|0.5|USoz|mL|abbr=on}} alcohol by volume</small>
|-
! scope="col" rowspan="2" | Drinks
! scope="col" rowspan="2" | Sex
! scope="col" colspan="9" | Body weight
|-
! scope="col" class="nowrap" | 40&nbsp;kg<br />90&nbsp;lb
! scope="col" class="nowrap" | 45&nbsp;kg<br />100&nbsp;lb
! scope="col" class="nowrap" | 55&nbsp;kg<br />120&nbsp;lb
! scope="col" class="nowrap" | 64&nbsp;kg<br />140&nbsp;lb
! scope="col" class="nowrap" | 73&nbsp;kg<br />160&nbsp;lb
! scope="col" class="nowrap" | 82&nbsp;kg<br />180&nbsp;lb
! scope="col" class="nowrap" | 91&nbsp;kg<br />200&nbsp;lb
! scope="col" class="nowrap" | 100&nbsp;kg<br />220&nbsp;lb
! scope="col" class="nowrap" | 109&nbsp;kg<br />240&nbsp;lb
|-
| rowspan="2" | 1 || Male || – || 0.04 || 0.03 || 0.03 || 0.02 || 0.02 || 0.02 || 0.02 || 0.02
|-
| Female || 0.05 || 0.05 || 0.04 || 0.03 || 0.03 || 0.03 || 0.02 || 0.02 || 0.02
|-
| rowspan="2" | 2 || Male || – || 0.08 || 0.06 || 0.05 || 0.05 || 0.04 || 0.04 || 0.03 || 0.03
|-
| Female || 0.10 || 0.09 || 0.08 || 0.07 || 0.06 || 0.05 || 0.05 || 0.04 || 0.04
|-
| rowspan="2" | 3 || Male || – || 0.11 || 0.09 || 0.08 || 0.07 || 0.06 || 0.06 || 0.05 || 0.05
|-
| Female || 0.15 || 0.14 || 0.11 || 0.10 || 0.09 || 0.08 || 0.07 || 0.06 || 0.06
|-
| rowspan="2" | 4 || Male || – || 0.15 || 0.12 || 0.11 || 0.09 || 0.08 || 0.08 || 0.07 || 0.06
|-
| Female || 0.20 || 0.18 || 0.15 || 0.13 || 0.11 || 0.10 || 0.09 || 0.08 || 0.08
|-
| rowspan="2" | 5 || Male || – || 0.19 || 0.16 || 0.13 || 0.12 || 0.11 || 0.09 || 0.09 || 0.08
|-
| Female || 0.25 || 0.23 || 0.19 || 0.16 || 0.14 || 0.13 || 0.11 || 0.10 || 0.09
|-
| rowspan="2" | 6 || Male || – || 0.23 || 0.19 || 0.16 || 0.14 || 0.13 || 0.11 || 0.10 || 0.09
|-
| Female || 0.30 || 0.27 || 0.23 || 0.19 || 0.17 || 0.15 || 0.14 || 0.12 || 0.11
|-
| rowspan="2" | 7 || Male || – || 0.26 || 0.22 || 0.19 || 0.16 || 0.15 || 0.13 || 0.12 || 0.11
|-
| Female || 0.35 || 0.32 || 0.27 || 0.23 || 0.20 || 0.18 || 0.16 || 0.14 || 0.13
|-
| rowspan="2" | 8 || Male || – || 0.30 || 0.25 || 0.21 || 0.19 || 0.17 || 0.15 || 0.14 || 0.13
|-
| Female || 0.40 || 0.36 || 0.30 || 0.26 || 0.23 || 0.20 || 0.18 || 0.17 || 0.15
|-
| rowspan="2" | 9 || Male || – || 0.34 || 0.28 || 0.24 || 0.21 || 0.19 || 0.17 || 0.15 || 0.14
|-
| Female || 0.45 || 0.41 || 0.34 || 0.29 || 0.26 || 0.23 || 0.20 || 0.19 || 0.17
|-
| rowspan="2" | 10 || Male || – || 0.38 || 0.31 || 0.27 || 0.23 || 0.21 || 0.19 || 0.17 || 0.16
|-
| Female || 0.51 || 0.45 || 0.38 || 0.32 || 0.28 || 0.25 || 0.23 || 0.21 || 0.19
|- class="sortbottom"
| colspan="11" style="text-align: center" | Subtract approximately 0.01 every 40 minutes after drinking.
|}

===By training===
If individuals are asked to estimate their BAC, then given accurate feedback via a breathalyzer, and this procedure is repeated a number of times during a drinking session, studies show that these individuals can learn to discriminate their BAC, to within a mean error of 9&nbsp;mg/100 mL (0.009% BAC).<ref>{{cite journal |last1=Huber |first1=H |last2=Karlin |first2=R |last3=Nathan |first3=P E |title=Blood alcohol level discrimination by nonalcoholics. The role of internal and external cues. |journal=Journal of Studies on Alcohol |date=January 1976 |volume=37 |issue=1 |pages=27–39 |doi=10.15288/jsa.1976.37.27|pmid=2811 }}</ref> The ability is robust to different types of alcohol, different drink quantities, and drinks with unknown levels of alcohol. Trained individuals can even drink alcoholic drinks so as to adjust or maintain their BAC at a desired level.<ref>{{cite journal |last1=Rowan |first1=D. C. |title=The Role of Blood Alcohol Level Estimation in Training Alcoholics to become Controlled Drinkers |journal=British Journal of Addiction to Alcohol & Other Drugs |date=March 1978 |volume=73 |issue=3 |pages=316–318 |doi=10.1111/j.1360-0443.1978.tb00159.x|pmid=280356 }}</ref> Training the ability does not appear to require any information or procedure besides breathalyzer feedback, although most studies have provided information such as intoxication symptoms at different BAC levels. Subjects continue to retain the ability one month after training.<ref>{{cite journal |last1=Kelly |first1=Alexandra R. |last2=Fillmore |first2=Mark T. |title=Use of mindfulness training to improve BAC self-estimation during a drinking episode. |journal=Psychology of Addictive Behaviors |date=24 August 2023 |volume=38 |issue=3 |pages=305–314 |doi=10.1037/adb0000955|pmid=37616096 |pmc=10907993 |s2cid=261098937 }}</ref>

===Post-mortem===
After fatal accidents, it is common to check the blood alcohol levels of involved persons. However, soon after death, the body begins to [[Putrefaction|putrefy]], a biological process which produces ethanol. This can make it difficult to conclusively determine the blood alcohol content in autopsies, particularly in bodies recovered from water.<ref>{{Cite journal |last1=Kugelberg |first1=Fredrik C. |last2=Jones |first2=Alan Wayne |date=5 January 2007 |title=Interpreting results of ethanol analysis in postmortem specimens: A review of the literature |url=https://www.sciencedirect.com/science/article/pii/S0379073806002891 |journal=[[Forensic Science International]] |volume=165 |issue=1 |pages=10–27 |doi=10.1016/j.forsciint.2006.05.004 |pmid=16782292 |access-date=20 May 2020}}</ref><ref>{{Cite journal|url=https://pubmed.ncbi.nlm.nih.gov/20232748/|pmid = 20232748|year = 2010|last1 = Xie|first1 = Y.|last2 = Deng|first2 = Z. H.|title = Analysis of alcohol mass concentration in corpse blood|journal = Fa Yi Xue Za Zhi|volume = 26|issue = 1|pages = 59–63}}</ref><ref>{{Cite journal|url=https://pubmed.ncbi.nlm.nih.gov/8373563/|pmid = 8373563|year = 1993|last1 = Felby|first1 = S.|last2 = Nielsen|first2 = E.|title = Postmortem blood alcohol concentration|journal = Blutalkohol|volume = 30|issue = 4|pages = 244–250}}</ref><ref>{{Cite journal|url=https://doi.org/10.1016/j.yrtph.2016.03.020|doi = 10.1016/j.yrtph.2016.03.020|title = Best-practices approach to determination of blood alcohol concentration (BAC) at specific time points: Combination of ante-mortem alcohol pharmacokinetic modeling and post-mortem alcohol generation and transport considerations|year = 2016|last1 = Cowan|first1 = Dallas M.|last2 = Maskrey|first2 = Joshua R.|last3 = Fung|first3 = Ernest S.|last4 = Woods|first4 = Tyler A.|last5 = Stabryla|first5 = Lisa M.|last6 = Scott|first6 = Paul K.|last7 = Finley|first7 = Brent L.|journal = Regulatory Toxicology and Pharmacology|volume = 78|pages = 24–36|pmid = 27041394}}</ref> For instance, following the 1975 [[Moorgate tube crash]], the driver's kidneys had a blood alcohol concentration of 80&nbsp;mg/100&nbsp;mL, but it could not be established how much of this could be attributed to natural decomposition.<ref>{{cite news|title=Moorgate Alcohol Finding|work=The Guardian|date=16 April 1975|page=24}}</ref> Newer research has shown that vitreous (eye) fluid provides an accurate estimate of blood alcohol concentration that is less subject to the effects of decomposition or contamination.<ref>{{cite journal |last1=Savini |first1=F |last2=Tartaglia |first2=A |last3=Coccia |first3=L |last4=Palestini |first4=D |last5=D'Ovidio |first5=C |last6=de Grazia |first6=U |last7=Merone |first7=GM |last8=Bassotti |first8=E |last9=Locatelli |first9=M |title=Ethanol Determination in Post-Mortem Samples: Correlation between Blood and Vitreous Humor Concentration. |journal=Molecules (Basel, Switzerland) |date=12 June 2020 |volume=25 |issue=12 |page=2724 |doi=10.3390/molecules25122724|doi-access=free |pmid=32545471|pmc=7355602 }}</ref>

== Legal limits ==
{{Main|Drunk driving law by country}}
[[File:Map of European countries by maximum blood alcohol level.svg|thumb|right|300px|Map of Europe showing countries' blood alcohol limits as defined in g/dL for the general population]]

For purposes of law enforcement, blood alcohol content is used to define intoxication and provides a rough measure of impairment. Although the degree of impairment may vary among individuals with the same blood alcohol content, it can be measured objectively and is therefore legally useful and difficult to contest in court. Most countries forbid operation of motor vehicles and heavy machinery above prescribed levels of blood alcohol content. Operation of boats and aircraft is also regulated. Some jurisdictions also regulate bicycling under the influence. The alcohol level at which a person is considered legally impaired to drive varies by country.

== Test assumptions ==

===Extrapolation===
Retrograde [[extrapolation]] is the mathematical process by which someone's blood alcohol concentration at the time of driving is estimated by projecting backwards from a later chemical test. This involves estimating the absorption and elimination of alcohol in the interim between driving and testing. The rate of elimination in the average person is commonly estimated at 0.015 to 0.020&nbsp;grams per deciliter per hour (g/dL/h),<ref>{{cite journal |doi=10.1080/15287399209531639 |title=Retrograde extrapolation of blood alcohol data: An applied approach |year=1992 |last1=Montgomery |first1=Mark R. |last2=Reasor |first2=Mark J. |journal=Journal of Toxicology and Environmental Health |volume=36 |issue=4 |pages=281–92 |pmid=1507264|bibcode=1992JTEHA..36..281M }}</ref> although again this can vary from person to person and in a given person from one moment to another. Metabolism can be affected by numerous factors, including such things as body temperature, the type of alcoholic beverage consumed, and the amount and type of food consumed.

In an increasing number of states, laws have been enacted to facilitate this speculative task: the blood alcohol content at the time of driving is legally presumed to be the same as when later tested.  There are usually time limits put on this presumption, commonly two or three hours, and the defendant is permitted to offer evidence to rebut this presumption.

Forward extrapolation can also be attempted. If the amount of alcohol consumed is known, along with such variables as the weight and sex of the subject and period and rate of consumption, the blood alcohol level can be estimated by extrapolating forward. Although subject to the same infirmities as retrograde extrapolation—guessing based upon averages and unknown variables—this can be relevant in estimating BAC when driving and/or corroborating or contradicting the results of a later chemical test.

==Metabolism==
{{Main|Pharmacology of ethanol#Pharmacokinetics}}
The [[pharmacokinetic]]s of ethanol are well characterized by the [[ADME]] acronym (absorption, distribution, metabolism, excretion). Besides the dose ingested, factors such as the person's [[total body water]], speed of drinking, the drink's nutritional content, and the contents of the stomach all influence the profile of blood alcohol content (BAC) over time. Breath alcohol content (BrAC) and BAC have similar profile shapes, so most forensic pharmacokinetic calculations can be done with either. Relatively few studies directly compare BrAC and BAC within subjects and characterize the difference in pharmacokinetic parameters. Comparing arterial and venous BAC, arterial BAC is higher during the absorption phase and lower in the postabsorptive declining phase.<ref name="Jones2019">{{cite journal |last1=Jones |first1=Alan W. |title=Alcohol, its absorption, distribution, metabolism, and excretion in the body and pharmacokinetic calculations |journal=WIREs Forensic Science |date=September 2019 |volume=1 |issue=5 |doi=10.1002/wfs2.1340|doi-access=free}}</ref>

== Highest levels ==
{{See also|List of deaths through alcohol}}
{| class="wikitable sortable"
! Date !! BAC (%) !! Location !! Description !! Result (died or survived) !! Cause of Death (If Died)
|-
| 1982 
|data-sort-value=1.33| 1.33 BAC, approximated from 1.51 SAC
|| [[Los Angeles, California]], [[United States|USA]]
|| A 24-year-old woman was admitted to the UCLA emergency room with a serum alcohol content of 1.51%, corresponding to a blood alcohol content of 1.33%. She was alert and oriented to person and place and survived.<ref>{{cite journal |doi=10.1016/S0140-6736(82)91285-5 |title=Survival After a Serum Ethanol Concentration of 11/2% |year=1982 |last1=Johnson |first1=R |journal=The Lancet |volume=320 |issue=8312 |pages=1394|pmid=6129476 |s2cid=27551241 }}</ref> Serum alcohol concentration is not equal to nor calculated in the same way as blood alcohol content.<ref>{{cite journal |bibcode=2002JChEd..79..803L |doi=10.1021/ed079p803 |title=Conversion of Serum-Alcohol Concentrations to Corresponding Blood-Alcohol Concentrations |year=2002 |last1=Labianca |first1=Dominick A. |journal=Journal of Chemical Education |volume=79 |issue=7 |pages=803|doi-access=free }}</ref> 
|| Survived
||
|-
| 1984 
|| 1.50 
|| 
|| A 30-year-old man survived a blood alcohol concentration of 1.5% after vigorous medical intervention that included [[Kidney dialysis|dialysis]] and [[intravenous therapy]] with [[fructose]].<ref>{{cite journal |doi=10.1001/archinte.1984.00350150255052 |title=Survival After High Blood Alcohol Levels: Association with First-Order Elimination Kinetics |year=1984 |last1=O'Neill |first1=Shane |journal=Archives of Internal Medicine |volume=144 |issue=3 |pages=641–2 |pmid=6703836 |last2=Tipton |first2=KF |last3=Prichard |first3=JS |last4=Quinlan |first4=A}}</ref>
|| Survived
|| 
|-
| 1995 
|| 1.48 
|| [[Wrocław]], [[Poland]] 
||  In 1995, a man from [[Wrocław]], Poland, caused a car accident near his hometown. He had a blood alcohol content of 1.48%; he was tested five times, with each test returning the same reading. He died a few days later of injuries from the accident.<ref name="eOstroleka 2012"/>
|| Died
|| Injuries from a car accident
|-
| 2004 
|| 1.35 
|| Taiwan 
|| In 2004, an unidentified Taiwanese woman died of alcohol intoxication after immersion for twelve hours in a bathtub filled with 40% ethanol. Her blood alcohol content was 1.35%. It was believed that she had immersed herself as a response to the  [[2002–2004 SARS outbreak|early 2000s outbreak]] of [[SARS]].<ref>{{cite journal |doi=10.1016/j.forsciint.2004.06.014 |title=Fatal alcohol immersion during the SARS epidemic in Taiwan |year=2005 |last1=Wu |first1=Yen-Liang |last2=Guo |first2=How-Ran |last3=Lin |first3=Hung-Jung |journal=Forensic Science International |volume=149 |issue=2–3 |pages=287 |pmid=15749375|pmc=7131152 }}</ref>
|| Died 
|| Alcohol intoxication
|-
| 22 Dec 2010 
|| 1.60 
|| Queenstown, South Africa 
|| In South Africa, a man driving a [[Mercedes-Benz Vito]] light van containing 15 sheep allegedly stolen from nearby farms was arrested on December 22, 2010, near [[Queenstown, Eastern Cape|Queenstown]] in [[Eastern Cape]]. His blood had an alcohol content of 1.6%. Also in the vehicle were five boys and a woman, who were also arrested.<ref>{{cite news |url=https://www.sowetanlive.co.za/news/2010-12-24-drunkest-driver-in-sa-arrested/ |title=Drunkest driver in SA arrested |work=Sowetan |date=24 December 2010 |access-date=31 March 2022 |first=Sibongile |last=Mashaba }}</ref>{{Dubious|date=December 2023|reason=It appears dubious that 15 sheep could be accommodated in the same vehicle alongside 6 people. Furthermore, there are concerns regarding the reported blood alcohol content, given that multiple sources instead cite the highest recorded blood alcohol content as 1.48% in the context of the Polish case. Additional verification is needed to confirm the accuracy of these details.}}
|| Survived
|| 
|-
| 26 Oct 2012 
|data-sort-value=2.23| 2.23 (possible contamination)
|| [[Gmina Olszewo-Borki]], [[Poland]]
|| A man from [[Gmina Olszewo-Borki]], Poland, who died in a car accident, recorded a blood alcohol content of 2.23%; however, the blood sample was collected from a wound and thus possibly contaminated.<ref name="eOstroleka 2012">{{cite web|last1=Łuba|first1=Marcin|title=Śmiertelny rekord: Kierowca z powiatu ostrołęckiego miał 22 promile alkoholu! Zginął w wypadku|url=http://www.eostroleka.pl/smiertelny-rekord-kierowca-z-powiatu-ostroleckiego-mial-22-promile-alkoholu-zginal-w-wypadku-zdjecia,art31892.html|website=eOstroleka.pl|access-date=2017-11-04|language=pl|date=24 October 2012}}</ref>
|| Died
|| Injuries from a car accident 
|-
| 26 July 2013 
|| 1.374
|| [[Alfredówka]], [[Poland]] 
|| A 30-year-old man from [[Alfredówka]], Poland, was found by Municipal Police Patrol from [[Nowa Dęba]] lying in the ditch along the road in Tarnowskiej Woli. At the hospital, it was recorded that the man had a blood alcohol content of 1.374%. The man survived.<ref>{{cite web|url=http://wiadomosci.gazeta.pl/wiadomosci/1,114871,14402847,Mial_13_74_promila_alkoholu_we_krwi__I_przezyl__Rekord.html |trans-title=He had 13.74 blood alcohol levels. And he survived. World record? |title=Miał 13,74 promila alkoholu we krwi. I przeżył. Rekord świata? |access-date=2013-08-08 |url-status=dead |archive-url=https://web.archive.org/web/20130811065906/http://wiadomosci.gazeta.pl/wiadomosci/1%2C114871%2C14402847%2CMial_13_74_promila_alkoholu_we_krwi__I_przezyl__Rekord.html |archive-date=2013-08-11 }}</ref><ref>{{cite web|url=http://www.nowadeba.pl/mieszkaniec/bezpieczenstwo/straz-miejska/informacje/art,864,straznicy-miejscy-uratowali-zycie-mieszkanca-alfredowki-.html|title=Informacje}}</ref>

|| Survived 
|
|}

==Notes==
{{notelist}}

== References ==
=== Citations ===
{{Reflist}}

===General and cited references ===
* Carnegie Library of Pittsburgh. Science and Technology Department. ''The Handy Science Answer Book''. Pittsburgh: The Carnegie Library, 1997. {{ISBN|978-0-7876-1013-5}}.
* {{cite journal |doi=10.1111/j.1360-0443.2006.01699.x |title=Identifying drunkenness in the night-time economy |year=2007 |last1=Perham |first1=Nick |last2=Moore |first2=Simon C. |last3=Shepherd |first3=Jonathan |last4=Cusens |first4=Bryany |journal=Addiction |volume=102 |issue=3 |pages=377–80 |pmid=17298644}}
* Taylor, L., and S. Oberman. ''Drunk Driving Defense'', 6th edition. New York: Aspen Law and Business, 2006. {{ISBN|978-0-7355-5429-0}}.

== External links ==
{{Commons category|Blood alcohol content statistics}}
* [https://www.mdcalc.com/estimated-ethanol-toxic-alcohol-serum-concentration-based-ingestion Estimated alcohol]

{{Alcohol and health}}
{{Authority control}}

[[Category:Alcohol law]]
[[Category:Alcohol policy]]
[[Category:Concentration indicators]]
[[Category:Driving under the influence]]
[[Category:Metabolism]]