Collect SST/1 mL serum, after 30 minutes of clotting, promptly centrifuge and send.

Alternate sample: Red top

Patient preparation: This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.