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Updated on September 8, 2023
5 min read

Can a Blood Test Show Heavy Drinking?

A simple blood test can provide valuable insight by analyzing critical biomarkers associated with excessive drinking. 

If you’re curious about how your drinking habits can affect blood test results, it’s crucial to understand the impacts alcohol may have on your health.

How Does Alcohol Affect Blood Test Results?

If you’re getting blood work done, it’s best to abstain from alcohol consumption—especially for a fasting blood test. Drinking alcohol can affect blood sugar, cause irregular enzymes and fat levels, and give inaccurate blood test results.

Alcohol’s Effects On the Body

When alcohol is consumed, it can disrupt the balance of glucose regulation in the body, as it impairs the liver’s ability to produce glucose and may lead to hypoglycemia. 

Additionally, alcohol can alter enzyme activity and fat metabolism in the liver, affecting various blood test components and leading to inaccurate readings, especially in tests that rely on liver function markers and lipid levels.

Blood Tests Affected by Alcohol Consumption

Avoid drinking alcohol before taking these certain blood tests, especially the night before:

  • Cholesterol test
  • Triglyceride test
  • Lipid panel blood test
  • Blood glucose test
  • Hepatitis test
  • Liver function test

Consult a healthcare professional for more medical advice if you have further questions or want to explore treatment options/resources.


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How Long Should You Not Drink Alcohol Before a Blood Test?

A standard blood test can detect alcohol up to 12 hours after you consume it. But the body may need up to 25 hours to fully metabolize and clear a moderate amount of alcohol from your system.

If you need to fast before a blood test, apart from avoiding food and other beverages, refrain from consuming alcohol for at least 24 hours before it. 

But since some blood tests are specific to liver enzymes, it is still best to ask your health provider when you should start avoiding alcohol for your blood test.

Blood Tests and Heavy Alcohol Consumption

Blood tests are one of the most reliable methods for detecting heavy alcohol consumption. They can also effectively measure blood alcohol content (BAC).

Though they can reveal the extent of a person’s alcohol intake, blood alcohol tests are only reliable for 6 to 12 hours after the last drink. In general, blood tests help identify the following:

  • Liver disease or damage
  • Excessive alcohol use
  • Changes in alcohol consumption during recovery

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Direct and Indirect Biomarkers for a Blood Test

Blood tests are valuable tools used in measuring blood alcohol concentration. Between direct and indirect biomarkers, direct biomarkers are considered more accurate, with an accuracy rate of 99%.

effectiveness of biomarker

Most blood tests rely on direct and indirect biomarkers, which show how a person’s organs function. 

  • Indirect Biomarkers: Alcohol consumption directly influences them; other factors can also impact these markers.
  • Direct Biomarkers: They exclusively stem from alcohol consumption, rendering them a reliable measure of the quantity of alcohol you ingest. 

Accuracy of Biomarkers

In the past, blood tests relied on indirect markers to determine BAC. In some cases, indirect biomarker tests are as low as 44% accurate.

Direct biomarker testing is approximately 99% accurate. Blood test results for direct biomarkers are even more reliable when confirmed through fingernail and hair testing. 


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CDT Testing for Alcohol Abuse

CDT Testing, short for carbohydrate-deficient transferrin, is a blood test used as an alcohol biomarker. These tests help determine if someone is:

Transferrin is a protein in the blood that is crucial in transporting iron throughout the body. When someone drinks too much, it increases certain types of transferrin that are carbohydrate-deficient.

How It Works

CDT testing measures the amount of carbohydrate-deficient transferrin in a person’s system. Non-drinkers have lower levels of carbohydrate-deficient transferrin. 

On the other hand, heavy drinkers tend to have significantly higher levels of it due to their regular consumption of four or more drinks daily (at least five days a week for two weeks before the test).

Effectiveness of CDT Tests

CDT testing is accurate but not foolproof. This is because heavy drinking doesn’t increase carbohydrate-deficient transferrin for everyone. However, it remains the only test sensitive enough to detect relapse or reduction in alcohol use. 

Many therapists use CDT testing to determine a baseline level when treatment begins. If medical professionals suspect someone is drinking with low carbohydrate-deficient transferrin, they encourage follow-up use of other alcohol biomarker tests for the most accurate results.

Alcohol Use Biomarkers

Other biomarker tests support or disprove the results of a CDT test. The best tests are easy to obtain, inexpensive to evaluate, and acceptable to therapists and those receiving medical treatment. 

However, selecting the proper blood test depends significantly on the person undergoing the exam. 

The selection of biomarkers may vary based on several factors, including:

  • Age
  • Gender
  • Ethnicity
  • Health status

Types of Biomarkers

Each biomarker testing method has advantages and disadvantages. Many types of biomarkers indirectly indicate blood alcohol exposure or consumption. Age, gender, health status, and ethnicity affect different biomarkers.  

Experts recommend using a combination of varying biomarker tests to get accurate results and confirm the status of a person’s alcohol intake.

Biomarkers That Detect a High Level of Alcohol Exposure

Biomarkers for Chronic Alcohol Use 

  • Carbohydrate-deficient transferrin (CDT)
  • Phosphatidylethanol (PEth)

Nonspecific Markers

  • Aspartate aminotransferase (AST)
  • Alanine aminotransferase (ALT)
  • Gamma-glutamyl transferase (GGT)
  • Mean corpuscular volume (MCV)

Alcohol Use Statistics



of Americans suffered Alcohol Use Disorder in 2020.



of Americans ages 18 and older reported that they engaged in binge drinking.



people have alcohol use disorder (AUD).

  • Alcohol use disorder (AUD) affected almost 30 million people in the U.S. in 2020, representing 10.6% of those aged 12 and over.7
  • In 2020, 894,000 adolescents between the ages of 12 and 17 presented indicators of AUD, which translates to 3.4% of the age group. Amongst this group, boys accounted for 298,000 (2.2%), whereas girls represented 596,000 (4.7%).7
  • 16.6 million males and 13 million females over 12 were afflicted with AUD in 2020. These figures represent 12.1% and 9.1% of their age groups, respectively.7
  • 28.6 million American adults, approximately 11.3% of the adult population, experienced AUD in 2020. Within this group, 16.3 million were male, and 12.4 million were female, representing 13.2% and 9.5% of their respective age groups.7
  • In 2021, 14.8 million Americans were diagnosed with AUD. Men bear the brunt of this affliction with 61.74% of cases, while women and adolescents comprise 35.57% and 2.69%, respectively. 
  • While many American adults drink alcohol, a concerning 6.7% will ultimately develop the disease.9
  • More than 90,000 Americans pass away annually due to alcohol-related causes.9
Updated on September 8, 2023
11 sources cited
Updated on September 8, 2023
All Alcoholrehabhelp content is medically reviewed or fact checked to ensure as much factual accuracy as possible.

We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies.
  1. Liang et al. “Evaluation of the diagnostic utility of carbohydrate-deficient transferrin in chronic alcoholism: Results from Southwest China.” Medicine, 2021.
  2. Allen et al. “Biomarkers of Heavy Drinking.” National Institute on Alcohol Abuse and Alcoholism, 2019.
  3. How Testing Blood for Alcohol Abuse Works: Options Listed.” DNA Legal, 2016.
  4. Cabezas et al. “Biomarkers for Monitoring Alcohol Use.” American Association for the Study of Liver Diseases, 2016.
  5. U.S. Department of Health and Human Services. “Alcohol facts and statistics.” National Institute on Alcohol Abuse and Alcoholism, 2023.
  6. Andresen-Streichert et al. “Alcohol Biomarkers in Clinical and Forensic Contexts.” Deutsches Ärzteblatt International, 2018.
  7. U.S. Department of Health and Human Services. “Alcohol Use Disorder (AUD) in the United States: Age Groups and Demographic Characteristics.” National Institute on Alcohol Abuse and Alcoholism, 2023.
  8. Alcohol Abuse Statistics.” National Center for Drug Abuse Statistics, 2023.
  9. Stilley, W. “More people drank excessively during the pandemic. the world must tackle its alcohol problem.” World Economic Forum, 2021.
  10. How Long Does Alcohol Stay in Your System?” Cleveland Clinic, 2022.
  11. Blood tests: fasting. Sullivan Nicolaides Pathology, 2021.
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All content created by Alcohol Rehab Help is sourced from current scientific research and fact-checked by an addiction counseling expert. However, the information provided by Alcohol Rehab Help is not a substitute for professional treatment advice.
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