AI Summary A CDT test measures carbohydrate-deficient transferrin in blood and serves as an alcohol biomarker. Other markers include EtG, GGT, and MCV. Doctors may order it when alcohol-related liver disease is suspected, to support recovery, or to plan advanced care. It does not diagnose liver disease on its own; your doctor reads it with your drinking history, other blood tests, and sometimes imaging. Stopping alcohol is the key treatment. Ask your care team what your result means.
Source: www.liverdirectory.com
Medically Reviewed.
CDT stands for carbohydrate-deficient transferrin. Transferrin is a protein in the blood that carries iron. Doctors can measure CDT as one of several alcohol biomarkers.
A CDT result is one piece of information. Your care team uses it to support your care, not to judge you.
Below, you will find key facts, how CDT fits with other alcohol markers, why doctors order it, what to expect, and answers to common questions.
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CDT blood test basics
A CDT test measures carbohydrate-deficient transferrin in a blood sample. Transferrin is a protein that carries iron through the blood. CDT is a form of this protein that doctors measure as an alcohol biomarker. An alcohol biomarker is a substance measured in the body that helps show whether a person has been drinking.
Doctors sort alcohol markers into two groups. Direct markers, such as ethyl glucuronide (EtG), come from the way the body processes alcohol itself. Indirect markers, such as the liver enzyme GGT and the red blood cell measure MCV, show how alcohol may be affecting the body. Indirect markers are less specific to alcohol. Urinary EtG is considered superior to GGT and MCV.
These tests matter in alcohol-related liver disease (ARLD), also called alcoholic liver disease or alcohol-associated liver disease. Stopping alcohol completely is vital to treating it. A biomarker result adds an objective lab finding to what you tell your care team.
For the full group of markers, see Alcohol Biomarker Testing. For treatment, see Alcohol-Related Liver Disease Treatment.
Direct vs indirect markers
No single test tells the whole story. Doctors choose a marker based on your situation and read it with your history.
| Marker | Sample | What to know |
|---|---|---|
| CDT (carbohydrate-deficient transferrin) | Blood | An alcohol biomarker your care team may use with other information. Your lab report explains how to read your result. |
| Urinary EtG (ethyl glucuronide) | Urine | A direct marker. It can detect alcohol use for up to 80 hours and is not influenced by cirrhosis. |
| Hair EtG | Scalp hair | Tracks drinking for up to six months. Each 1 cm segment reflects about one month. |
| GGT and MCV | Blood | Indirect markers. They show how alcohol may be affecting the body, and they are less specific to alcohol. |
For the blood-based PEth marker, see the PEth page.
Common reasons for testing
Doctors use alcohol biomarkers alongside your drinking history, not instead of it.
If your doctor suspects alcohol-related liver disease, they usually order blood tests to check how your liver works and ask about your alcohol use. Early stages such as fatty liver often cause few symptoms, so a lab result can help your team see the full picture. Imaging, a biopsy, or an endoscopy may follow in advanced disease.
Full abstinence is the key treatment for alcohol-related liver disease. Without it, no medical treatment can prevent further liver damage. Medicine, therapy, and support groups, especially in combination, help people stop drinking. A biomarker result can give you and your team a shared, objective way to track progress.
People with cirrhosis who keep drinking are not eligible for a liver transplant. Testing can be part of the regular check-ins that transplant and liver teams use to plan care.
Blood draw and results
A CDT test uses a blood sample, taken much like any routine blood draw. Ask your care team whether you need to prepare in any way and when results will be ready.
A CDT result is one piece of information. It does not diagnose liver disease on its own. Your doctor reads it with your drinking history, other blood tests, and sometimes imaging. The reference range and cutoff depend on the lab, so use the ranges printed on your report.
Ask what the result means for your liver, which other alcohol markers you might need, and how often to repeat testing. If you want to stop drinking, ask about medicine, therapy, and support groups. Talk with your doctor before you stop, because a doctor can help you find an approach that is right for you.
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Common Questions
A CDT test measures carbohydrate-deficient transferrin in a blood sample. Transferrin is a protein that carries iron through the blood, and CDT is a form of it. Doctors measure CDT as an alcohol biomarker, which is a substance in the body that helps show whether a person has been drinking. Your care team reads the result together with your drinking history and other tests. This page gives no cutoff numbers, because your lab report explains what applies to your result.
This page does not classify CDT. Doctors sort alcohol markers into two groups. Direct markers, such as EtG, come from the way the body processes alcohol itself. Indirect markers, such as GGT and MCV, show how alcohol may be affecting the body, and they are less specific to alcohol. Ask your care team how CDT fits into your care and which markers they plan to use.
No. A CDT result is one piece of information and does not diagnose liver disease on its own. If your doctor suspects alcohol-related liver disease, they usually order a blood test to check how your liver works and ask about your alcohol use. In more advanced disease, you may also need imaging such as an MRI, ultrasound, or CT scan, a liver biopsy, or an endoscopy. Early stages often cause only minor symptoms, so a lab result can help your team see the full picture.
This page does not give a CDT detection window. Other markers have known windows. Urinary EtG can detect alcohol use for up to 80 hours, and EtG in scalp hair can track drinking for up to six months, with each 1 cm segment reflecting about one month. Ask your care team how long CDT can show a result and how often they suggest repeating the test.
Talk with your doctor. Stopping alcohol completely is the key treatment for alcohol-related liver disease, and without it no medical treatment can prevent further liver damage. Early alcohol-related fatty liver can be reversed when a person stops drinking. Scarring from cirrhosis cannot, but it is never too late to quit, and stopping can halt the disease from getting worse. People with cirrhosis who keep drinking are not eligible for a liver transplant. Medicine, therapy, and support groups, especially together, help many people stop drinking. Depending on how well your liver works, medicine may not be an option, so a doctor can help you find an approach that is right for you.
Medical disclaimer: LiverDirectory provides educational information and a directory of providers. It does not provide medical advice, diagnosis, or treatment. Always consult a licensed physician regarding any medical condition.
