Optimal: Red

Acceptable: Gold**

**Acceptable if serum is separated from gel within 24 hours of collection.

4.5mL; full tube

1 mL whole blood

1.  Specimen should be drawn just prior to next dose (trough level).

2. A minimum of 2 hours prior to next dose is also acceptable.

3. Indicate time of last dose.

4. Gently invert the sample 5-6 times after collection.

Refrigerate

1. Allow the specimen to clot for 30 minutes.

2. Centrifuge specimen within 2 hours of collection.

3. After centrifugation, specimen tubes without a gel barrier should have the serum aliquoted to a false bottom container.

4. Keep the serum refrigerated until testing can be performed.