For a test of alcohol, of the alcohol marker ethylglucuronide, of CDT or the liver values (AST, ALT, GGT) the blood sample should be taken by medical staff. Blood or serum is also the most adequate specimen for monitoring medical drugs. Some drugs such as immune suppressive agents and also metals can be better measured in EDTA blood. Blood taken for analysis of illegal drugs particularly cocaine but also benzodiazepines (flunitrazepam) should be collected into a tube with sodium or potassium fluoride.
If blood transport to the laboratory is delayed, the samples should be kept in the refrigerator.