Ethanol
At a Glance
Why Get Tested?
To find out if a person has drunk alcohol and to measure the amount of alcohol present.
When to Get Tested?
When a patient has symptoms that suggest alcohol toxicity or when a person is suspected of breaking drinking-related laws or as part of a drug testing panel for pre-employment or other purposes.
Sample Required?
Ethanol (Ethyl alcohol) can be measured in blood sample, urine, saliva or in breath. Blood, urine, and saliva samples must be sent to a laboratory for analysis. A breath sample is analysed immediately on site using a Breathalyzer.
The Test Sample
What is being tested?
This test measures the amount of ethanol in the blood, urine, breath, or saliva. Ethanol (also called ethyl alcohol or alcohol) has been consumed by civilizations throughout the world for thousands of years. Small amounts of ethyl alcohol can cause excitement, relaxation, and decreased inhibition. Smaller amounts can cause poor judgment and eye-hand coordination; large amounts in a relatively short period of time can cause rapid alcohol poisoning with confusion, slow breathing, coma, and even death. Consumption of large quantities of alcohol over a long period of time can lead to alcoholism and to permanent liver damage.
When alcohol is drunk, it is absorbed by the stomach and intestine, and carried throughout the body in the bloodstream. Small amounts of ethanol are removed by the kidney in urine or breathed out from the lungs, but most is broken down by the liver. Alcohol is poisonous to the liver. With the help of enzymes, the liver oxidizes the alcohol first to acetaldehyde, then to acetate, and then finally to carbon dioxide and water. The liver can process about one drink an hour – with one drink being defined as the amount of alcohol in 250 mL (half a can) of beer, 80 mL (half a 175 mL glass) of wine, or a measure (25 mL) of whisky. A person who drinks more than 1 drink an hour will build up ethanol in their blood stream.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm; a breath sample is collected by blowing into a tube or balloon. Urine samples are collected in plastic containers; sometimes a single urine sample is collected and sometimes two separate samples may be collected with the first discarded and the second collected after a measured time. Saliva samples are often collected from the mouth using a swab.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
The Test
How is it used?
The ethanol/alcohol test is used for both medical and legal purposes. Samples and results for each use are usually collected and tested separately.
Medical: The doctor looks for alcohol to help treat the patient's symptoms. For medical purposes, blood, and sometimes urine, alcohol tests are used to detect the presence of ethanol and to measure its concentration. One or more of these tests may be requested when a patient is seen in the Accident and Emergency department with symptoms suggesting ethanol poisoning. The symptoms may include confusion, staggering, vomiting, tiredness, and unconsciousness. Other tests, such as a Full Blood Count (FBC), glucose and electrolytes are often ordered at the same time as there are a variety of other conditions that can cause similar symptoms. Additional drug testing and testing for the presence of other more toxic alcohols (such as methanol and isopropyl alcohol) may also be performed if the use of other substances is suspected.
Legal: Legal testing must be done by specially trained people and must have a strict chain-of-custody (a paper trail that records sample movement and handling). Testing may be requested to determine whether an erratic driver has a blood alcohol concentration that is over a legal limit, to determine whether an under-age child has been drinking, or to find out whether drinking alcohol has contributed to an accident. Post-mortem ethanol testing may be done to discover whether alcohol contributed to a person’s death. Legal ethanol testing may also be done randomly or as part of an employer's drug testing programme to see whether an employee has alcohol in their system.
Samples tested for legal purposes may include blood, breath, urine, and/or saliva testing. Breath testing is the most common test performed on drivers. It uses the tail end sample of breath from deep in the lungs and uses a conversion factor to estimate the amount of alcohol in the blood. Blood alcohol testing may be requested to confirm or refute other evidence, and/or be used as an alternative to breath testing. Urine testing may also be performed as an alternative. A random urine sample is sometimes used to monitor people for the presence of alcohol. Testing saliva for the presence of alcohol is not as widely used, but may be used as an alternative screening test.
When is it requested?
Medical ethanol testing is used when a patient has symptoms that suggest intoxication and or ethanol toxicity.
Legal ethanol testing may be requested whenever there is reason to suspect that a person has not followed a drinking-related law, and whenever there has been an accident and/or unexpected death – to determine whether alcohol played a role. Employment alcohol testing may be performed randomly and when the employer suspects that an employee has alcohol in their system while on the job.
What does the test result mean?
For medical testing, the detection of ethanol in a sample indicates that a person is likely to have been drinking, and the concentration present can give an indication of how severe the degree of ethanol toxicity is. Symptoms and complications may vary significantly from person to person, however, depending on the individual’s general health, age, and other medications or drugs that he or she is taking. The ability to remove all of the alcohol from the body also depends on the availability of the necessary liver enzymes and a healthy liver. For legal testing, results obtained are compared to legal allowable limits. In the UK (Feb 2009), the legal limit for driving is 80 milligrams/100 mL in blood, and 107 milligrams/100 mL in urine. The legal limit in breath samples is 35 micrograms of alcohol in 100 mL of breath.
Is there anything else I should know?
Different ethanol sample results are not interchangeable. Breath and urine samples are considered to be good estimates of blood alcohol concentrations in most people but can be affected by a variety of factors. Urine concentrations lag behind blood concentrations.
Urine samples that contain both glucose (such as may be seen in diabetics) and bacteria, should not be left at room temperature for long periods of time because the glucose can ferment and produce ethanol. Fermentation can also be seen in post mortem samples. Occasionally two other tests are used which measure serotonin metabolites, 5-HIAA (5-hydroxyindoleacetic acid) and 5-HTOL (5-hydroxytryptophol), which can help confirm whether alcohol was drunk. An increased ratio of 5-HTOL/5-HIAA can indicate alcohol consumption.
Breath sample concentrations can be affected by alcohol consumption within the last few minutes, ketones (released into the breath by some diabetics and dieters), and by other substances that contain alcohol such as mouthwash and cough syrup.
Common Questions
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Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
