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Lab Test: Ethanol (Ethyl Alcohol) Level

    Lab Test
    • Ethanol (Alcohol; Ethyl Alcohol) Level (serum)
    • Quantitative measurement of ethanol (ethyl alcohol) in the blood for the assessment of recent ethanol ("alcohol") ingestion.  Ethanol is one of the most well known depressants of the central nervous system and is commonly abused.
    Reference Range
    • Normal findings:  0-50 mg/dL or 0%-0.05%
    • Critical Values:  > 300 mg/dL or > 65 mmol/L (SI units)  (Note:  chronic alcoholics can commonly have levels > 300 mg/dL and begin to show signs of alcohol withdrawal even at elevated levels).
    Indications & Uses
    • Suspected alcohol intoxication - the blood ethanol level is typically elevated to 100 to 300 mg/dL (32.6 to 65.2 millimol/L) in acute intoxication.  Most fatalities occur with levels > 400 mg/dL (86.8 millimol/L).  The lethal dose is variable, depending in part on chronic versus sporadic ethanol use.  Minimal lethal exposure in a nontolerant adult is 5 to 6 g/kg of body weight taken orally.  In the pediatric population, minimum lethal exposure is 3 g/kg of body weight taken orally. 
    • Submersion - blood ethanol levels > 100 mg/100 dL have been reported in about one-third of adolescent and adult submersion victims.  Others have reported that 30% to 70% of submersion victims aged 15 years or older have alcohol in their blood.
    Clinical Application
    • Ethanol depresses the CNS and may cause reduced alertness, coma, and death.
    • Physiologic effects at specific ethanol concentrations:
      • Slowing of reflexes, impaired visual activity:  50 to 100 mg/dL (10.9 to 21.7 mmol/L)
      • CNS depression:  > 100 mg/dL (> 21.7 mmol/L)
      • Potentially fatal:  > 400 mg/dL (> 86.8 mmol/L)
    • The rate, but not extent, of alcohol absorption is affected by several factors, including the presence of food (particularly high-fat foods), amount of alcohol ingested, time frame for consumption, and metabolic differences among individuals.  On an empty stomach, peak blood ethanol level may occur in 30 to 75 minutes; on a full stomach or when large amounts of food have been consumed, peak level may not occur until 3 hours after ethanol ingestion.  Alcohol is metabolized in the liver.  A 70-kg person with normal liver function can metabolize about 15 mg of alcohol per hour. 
    • The universally accepted blood alcohol concentration results for legal purposes are reported in percent weight/volume units or g/dL truncated to 2 decimal places. 
    • The level of ethanol in blood equating to intoxication differs by state and country statute.
    •  Proper collection, handling, and storage of blood alcohol are important for medicolegal cases involving sobriety testing.   The blood test is the specimen of choice for legal purposes.
    Related Tests
    • Alanine Aminotransferase (ALT)
    • Aspartate Aminotransferase (AST)
    • Alkaline Phosphatase
    • Ethylene Glycol Level
    • Methanol Level
    Drug-Lab Interactions
    • Elevated blood ketones (as with diabetic ketoacidosis) can cause false elevation of blood test results. 
    • Alcohols others than ethanol (e.g., isopropyl [rubbing alcohol] or methanol [grain alcohol]) will also cause testing to be positive.
    Test Tube Needed
    • Gray-top or red-top, according to the agency's protocol.
    • Important!!  Use alcohol-free swabs, peroxide, or betadine when collecting the specimen.
    • Collect sample from an arm vein of a living person or from the aorta of a dead person.
    • Collect serum or whole blood sample (statutes defining BAC limits usually refer to whole blood as the biologic specimen).
    • Follow the institution's protocol if the specimen will be used for legal purposes. 
    • Apply pressure or a pressure dressing to the venipuncture site and assess the site for bleeding. 
    • The exact tine of specimen collection should be indicated. 
    • Also, signatures of the collector and a witness may be needed in some instances for legal evidence.
    Storage and Handling
    • Preserve with 1% sodium fluoride (weight/volume).
    • Store specimen with sodium fluoride at 25°C up to 2 weeks, at 5°C up to 3 months, and at -15°C up to 6 months. 
    • Store specimen without sodium fluoride at 25°C up to 2 days, 5°C up to 2 weeks, and at -15°C up to 4 weeks.
    What To Tell Patient Before & After
    • Explain the procedure to the patients. 
    • Patients should be advised of their legal rights.  This is usually best done by a law enforcement officer.  The alcohol level may be used as evidence for later court proceedings.
    1. LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.
    2. Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed.  St. Louis, Missouri. 2014.

MESH Terms & Keywords

  • Blood Alcohol Level, Blood Ethanol Level, Alcohol Level