CDT test: what your value says about alcohol use

You do not need to stop drinking beforehand. The test looks back at the weeks before it. If you want to show a decline, allow at least two to three weeks of abstinence. After years of heavy use it takes longer.

The Dutch guideline sets the cut-off at 2.0%. The upper limit of the normal reference interval is 1.7%. Measurement uncertainty is 0.3 percentage points. A value just over the line is therefore not conclusive on its own.

Up to 1.7% counts as normal on the standardised CDT-IFCC method. Laboratories may apply small differences in reference values. So always read the range printed on your own result.

Not from one evening with this measurement. It shows a pattern across roughly two to four weeks. For recent use, other tests suit better, such as EtG in urine.

Gamma-GT is a liver value and rises from far more than alcohol alone. This measurement is more specific. The guideline places CDT first and gamma-GT second.

Yes, as a pattern across recent weeks. For a fitness-to-drive assessment the guideline names CDT as the most suitable blood value, with gamma-GT second. CDT does not show a single evening of drinking. A test you order yourself does not count toward the CBR assessment and does not replace it.

Mainly CDT, and to a lesser degree gamma-GT. MCV, ASAT and ALAT were removed from the fitness-to-drive protocol in 2020 because they discriminated too poorly. For use in the last few days, EtG suits better than a blood value.

CDT reflects alcohol use across roughly two to four weeks. If you stop drinking, the value usually returns to normal within two to three weeks. After years of heavy drinking it often takes longer.

Only when a marker requires it; the test states it. Fasting is: only water after 22:00 the evening before, at least 8 hours. Leave out coffee and tea that morning, and the draw is before 10:00. Water is always allowed.

This screening costs €165,-, blood draw included. No draw costs are added; you pay yourself.

No, and you need not explain anything to your GP. We request a referral through ZorgDomein within one business day; orders after 17:00 or at the weekend count from the next business day. The ZorgDomein email holds a barcode for the draw site. At some draw sites you pick a time on your order page, or we book it.

No. A screening you request yourself falls outside the basic Dutch insurance. You pay it yourself, and it does not affect your deductible (eigen risico).

Count on one business day, because only then is the referral email in; without a referral you cannot go. After that, some draw sites see you in a walk-in session; the rest work by appointment. Each location tells you which.

The barcode from the ZorgDomein email and a valid ID. The barcode can simply be on your phone. No BSN? Then the email has no barcode and you print the referral form from the link in it.

Yes, take it as always, unless your own doctor decided otherwise. Some markers need more preparation, such as no alcohol for 24 hours. That is on the test and in the instructions with your order.

At the draw site you show the barcode and a valid ID, and then blood is taken. That takes about a quarter of an hour.

Yes, every result is assessed by a BIG-registered doctor, who explains the values in your account. Any treatment you discuss with your GP.

An independent, certified laboratory from the Zuivertest network, spread across the whole of the Netherlands. The laboratories also manage the draw sites; Zuivertest does not own them. Reference values can vary between laboratories.

No. The screening does not go through your GP and does not enter your medical record, and your employer receives nothing. Data goes to a healthcare provider only with your written consent and is never sold. Anonymous is not possible: a valid result asks for your name, date of birth and a valid ID.