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Types of BAC Testing

Donald Singleton
June 7, 2022

A blood alcohol level of 0.08% or higher is considered legally intoxicated in the United States, and you are prohibited from operating a vehicle. A breath test, a blood test, and a urine test are the three most common methods of determining blood alcohol concentration (BAC) in your body. In many states, you must submit to a breath test, but some allow you to submit to a blood test or urine test on request.


Scroll down to our Types of BAC Testing infographic:

Factors Affecting BAC Testing

You can read our legal resources for more information on what is a blood alcohol test.

What are the types of BAC Testing?

BAC Breath Test

A breathalyzer, or breath analysis device, is used by law enforcement to calculate BAC because it is lightweight, portable, and provides immediate results. A breathalyzer measures the amount of alcohol that is expelled from a subject’s body when blood flows through vessels in the lungs. The results of breathalyzers, especially those obtained with fuel-cell sensors, are deemed sufficiently accurate to be admissible in DUI cases.

Because breathalyzers assume test subjects share the same characteristics, they do not distinguish one individual from another. An averaged reading can be misleading. Diet and environmental factors can also affect the results of a breath test. These factors include paint, thinner, glue, and gasoline, among others. Blood tests are generally more accurate than breath tests.

The commercially available breathalyzer is an affordable and convenient way to test your BAC and make informed decisions about driving after drinking.

BAC Blood Test

A blood test usually requires your consent, and refusing to take one can have serious consequences, such as suspension of your license. According to the National Highway Traffic Safety Administration, refusers of blood alcohol tests receive higher fines and spend longer in jail than their counterparts who submit.

An analysis of a blood sample for blood alcohol content is generally more accurate than tests of breath or urine, however lab testing errors can occur, causing the test results to be inaccurate. In addition to coagulation, vial mix-ups, and fermentation of blood in the vial, factors such as lack of sterilization, preservatives, and refrigeration can affect accuracy.

BAC Urine Test

There are fewer accurate urine tests than breath or blood tests, and they are usually used only if other tests are unavailable. Like blood tests, urine tests are also deemed intrusive. According to studies, urine test results can be significantly different from blood test results.

The result of a urine test can vary depending on how long has passed after the incident, such as a traffic stop, since urine tests are typically not performed at the time of an incident. It can also take up to two hours for alcohol to appear in a person’s urine, and alcohol can remain in the body for up to 24 hours. Due to this, positive urine tests may not be proof that a person was under the influence of alcohol at the time of the incident.

Diluting or substituting urine samples can circumvent urine tests, unlike other types of testing. Validation of urine samples can be accomplished through temperature testing, but evidence of adulteration is difficult to establish. Both urine and blood tests are prone to laboratory errors.

EtG (ethyl glucuronide) tests have become increasingly popular in recent years because they can determine recent alcohol consumption even if there is no measurable alcohol present. The direct metabolite of alcohol, EtG, can be detected in the urine shortly after drinking.

As a result, the Substance Abuse and Mental Health Services Administration (SAMHSA) warns, EtG tests may not be reliable and can produce a “false positive,” or erroneous result. EtG may stay in urine for up to 80 hours, long after alcohol consumption has ended, and fails to distinguish between alcohol consumed and small amounts of alcohol found in hygiene, cosmetic, and household products, as well as some foods and medications. Moreover, SAMHSA warns that EtG tests are insufficiently specific to be used as primary or sole evidence that a person is prohibited from drinking.

People who are prohibited from drinking alcohol by their employers or the justice system can also use urine tests to verify abstinence and detect relapse.

Factors Affecting BAC

Several factors determine how fast and how long your blood alcohol level rises:

  1. Body weight. People who weigh more have a greater volume of water in their bodies. The more water in the body, the diluted the alcohol becomes.
  2. The gender. Women and men react differently to alcohol. Alcohol is broken down more quickly in men because they have a stomach enzyme that helps break it down. The average woman has fewer water and fat than a man. Women’s hormones can also impact their BAC.
  3. The number of drinks you had, how strong they were, and how fast you consumed them. A higher BAC increases with more drinking per hour.
  4. The amount of food you consume. Alcohol is processed more slowly when your stomach is full, especially when it’s high in protein.

Why Do These Results Matter?

Your blood alcohol content (BAC) may be over the legal limit of 0.08% if you are given a breath test by a police officer.

Additionally, a sample of your blood or urine may be required to determine a BAC in more detail.

You can always contact our car accident attorney in Georgia f you are involved in a car wreck case.

Factors affecting the blood alcohol test - Infographic
Donald Singleton

Donald Singleton


A Georgia native, Don founded Singleton Law Firm in 1999 as a continuation of his lifetime commitment to serving his state and community. He has concentrated his trial practice to representing victims of serious injury and wrongful death arising out of trucking, car, bus and motorcycle accidents, premises liability and a wide variety of other causes.

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