CDT Test (for alcohol misuse)

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Product Information

CDT Test (carbohydrate deficient transferrin) is a blood test used to check if a person has been drinking excessive quantities of alcohol over the previous 7-14 days.

CDT is a normal protein in the body and is present in all people. It only becomes elevated when a person drinks excessive amounts of alcohol regularly or even with binge drinking.

A CDT test is used by the DVLA when a person applies for their driving license to be reinstated. The DVLA accepts a CDT cut-off level of ≤ 2.2 %. A CDT test is also used by companies, such as Transport for London (TfL), who want to make sure an employee is not drinking excessively.

In our experience, the DVLA CDT tests can cause a lot of anxiety. Many of our clients order their own CDT test for for their own piece of mind before they attend for their official DVLA assessments. 

Alcohol in urine or blood can only be detected for 24-48 hours. Therefore, a CDT test is a better test for alcohol misuse because it checks a longer time-frame. An Alcohol Profile test is even better because it checks for changes in the blood and liver to assess the adverse effects of alcohol.

> Find out more

Proof of ID:

You should bring with you a valid photo ID such as a passport or driving license. No copies or mobile images are accepted. 


Results take 5 working days * and will be emailed to you. They include a doctor's explanation of the results. Please note that we do not give out results by telephone as this information is confidential and there is no way of identifying a caller.

* Indicative timings only. Actual result may be earlier or slightly later.


 liver-function-blood-test  Often combined with a liver function blood test to check for any damage to the liver from excessive alcohol consumption.


> Do a home CDT Test


 Causes of a high CDT level:

1. Alcohol Misuse (A 19 out of 20 chance): i.e. by far the most likely cause of a high CDT.

2. Liver Disease: Certain liver problems which cause a blockage or damage to bile ducts; e.g. primary biliary cirrhosis, primary sclerosing cholangitis, gallstones or liver/pancreatic cancer. These causes can be excluded if liver function tests (LFTs) are normal.

3. Transferrin Variants: Transferrin is a protein used to transport iron and can undergo changes by the consumption of alcohol. The normal type is C. People who have type D may have a raised CDT. Type D is rare in Caucasians but may be present in 10% of Africans. People with this variant cannot use CDT to check for alcohol misuse because CDT will always be high. We would recommend that these clients use a urine EtG test instead.

4. Carbohydrate deficient glycoprotein syndromes: these are very rare syndromes resulting in mental retardation in children.


How much alcohol will cause a high CDT level?

You need to drink the equivalent of 100-150g of alcohol per day to raise CDT levels. This equates to 5 pints of beer, a bottle of wine, or one-third of a bottle of spirits daily.

Intermittent or "binge" drinking can also raise CDT levels. This would have to be in the range of 200-300g of alcohol on two occasions per week (around double the above amount) and no alcohol on the other days. Just one day of excessive drinking with the other days of no alcohol would probably not be enough to raise CDT levels over a 7-14 day period.


Notes from the DVLA website

High risk offenders with alcohol problems

Defined in terms of the alcohol-related driving convictions below, the courts notify the DVLA of high risk offenders.

An independent medical examination will be arranged when an application for licence reinstatement is received by the DVLA. The assessment includes:

  • questionnaire
  • serum CDT assay
  • any further testing indicated.

If a licence is awarded, the ’til 70 licence is restored for Group 1 car and motorcycle driving. Consideration may be given to a Group 2 licence.

If a high risk offender has a previous history of alcohol dependence or persistent misuse but has satisfactory examination and blood tests, a short period licence is issued for ordinary and vocational entitlement but is dependent on their ability to meet the standards as specified.

A high risk offender found to have a current history of alcohol misuse or dependence and/or unexplained abnormal blood test results will have the application refused.


The high risk offender scheme applies to drivers convicted of the following:

  • one disqualification for driving or being in charge of a vehicle when the level of alcohol in the body equalled or exceeded either one of these measures:
    • 87.5 mcg per 100 ml of breath
    • 200.0 mg per 100 ml of blood
    • 267.5 mg per 100 ml of urine
  • two disqualifications within the space of 10 years for drinking-driving or being in charge of a vehicle while under the influence of alcohol
  • one disqualification for refusing or failing to supply a specimen for alcohol analysis
  • one disqualification for refusing to give permission for a laboratory test of a specimen of blood for alcohol analysis.


How it works

1. Please enter the name(s) and date of birth(s) of the person(s) taking the test at the top of the page. These details are essential to uniquely identify your sample by the laboratory and you will be unable to proceed further without them. 

2. Pay online by credit or debit card.

3. Initially, you will receive an automatic reply to confirm that we have received your instructions.

4. Your test request will then be processed between 9am-5pm, Monday-Friday. Once processed, you will receive a text message and email to confirm that you can now attend Patient Reception to have the test. Please wait for this confirmation before making your way to Patient Reception, otherwise they will be unaware that you will be attending.

5. You can attend Patient Reception at any time during opening hours of 7am-7pm, Monday-Friday, and 7am-1pm on Saturday. It is closed on Sundays and Public Holidays. The only exception is for Chain of Custody tests as these need an appointment.

7. Make sure to bring an original photo ID such as a passport or driving license. A copy or phone image is not acceptable.

8. Results will be sent by email as soon as they are available.

Date of Birth Requirement

All laboratories need information regarding the client to identify their individual sample.

Tests cannot be done without these details.

The minimum requirement is the full name and date of birth.

You can enter these details securely above. Personal details are subject to GDPR according to our Privacy Policy. Alternatively, you can email these to us at:

Photo ID Requirement

All laboratory tests need a photo ID to be shown at Patient Reception at the time of the test.

This is to ensure that it is the client who is taking the test.

Drug and alcohol test results often need to be shown to courts or other agencies and must be valid.

Only a valid passport or driving license is accepted.

Originals must be shown. No copies or images on a phone.


Patient Reception:

The Doctors Laboratory

76 Wimpole Street

Opening hours:
Monday to Friday:7.00am - 7.00pm
Saturday: 7.00am - 1.00pm









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