CDT Blood Test

Carbohydrate Deficient Transferrin Blood Test

  • Carbohydrate Deficient Transferrin (CDT) is a biomarker for heavy alcohol consumption.
  • Used by the DVLA in its fitness-to-drive test for high-risk offenders.
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Carbohydrate-deficient transferrin, known as “CDT,” is a blood test used to track excessive alcohol consumption over an extended period of time.


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What’s Included?

  • Venous blood collection appointment with our phlebotomist at your chosen location
  • CDT Test
  • Fast results by email

How does it work?

CDT tests are a measurement of a particularly sensitive alcohol biomarker present in the blood. The higher the quantity of alcohol consumed, then the higher the level of Carbohydrate Deficient Transferrin (CDT).

Transferrin remains in the circulatory system for 7 to 14 days and CDT, therefore, can give an indication of alcohol consumption over this period of time.

Why are you tested?

A CDT blood test is an objective way to screen and monitor clients who may suffer from alcohol abuse.

In addition to detecting heavy drinking in patients with alcohol-sensitive conditions, CDT testings can be used in the substance abuse field to monitor abstinence and relapse.

CDT testing also forms part of the DVLA medical following a Drink Drive conviction. The result of the blood test, alongside other information will then be used to make a decision as to whether or not a driving licence will be issued.

What does your %CDT blood test result mean?

If an individual drinks regularly, then the percentage of transferrin, which is deficient in carbohydrates will rise.

Below 1.6%

A %CDT result below 1.6 suggests no recent alcohol intake.

Between 1.6 and 2.2%

A %CDT result between 1.6 and 2.2 suggests recent alcohol excess alcohol intake.

Between 2.3 and 2.9%

A %CDT result between 2.3 and 2.9 indicates regular heavy amounts of alcohol consumption and can be an indication of increasing risk or higher risk drinking.

3.0% or higher

A %CDT result of 3 or more indicates regular excess amounts of alcohol consumption and can indicate alcohol dependence. Typically the level of alcohol intake required to produce a CDT result of 3.0% is 100-150 g alcohol per day. This equates to about 5 pints of beer, a bottle of wine or one third of a bottle of spirits daily.


After your blood test, you will receive blood results by email. You will then be able to use these to discuss with a Doctor.

Please note, your results will not diagnose any condition but will indicate if you should consult a doctor for any further action.

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