When urine or other matrices are not ideal, LabCorp offers drug testing of blood specimens. Blood analysis may be appropriate in situations when it is suspected that a person is actively under the influence of a drug or alcohol. Since drugs are rapidly metabolized and eliminated from the body, blood analysis offers a very brief detection window. Drugs in blood are typically detectable from minutes to hours depending on the drug and the dose versus one to several days in urine.

Initial testing is performed by a drug-specific enzyme immunoassay (ELISA), and confirmation analysis is performed by GC/MS. Standard profiles include the five to seven drug classes and detection levels.