Discard first morning urine then collect all urine for 24 hours, keep refrigerated throughout collection. Mix well and send 25.0 mL urine refrigerated in a screw-capped plastic urine container. Record total volume on container label.

Alternate collection with preservative: Refrigerate urine during collection (critical) and add 25.0 mL 6N HCl to the entire collection within 4 hours of collection completion. Mix collection well, and check pH to ensure pH is between 1 and 3. Send a 25.0 mL urine aliquot refrigerated in a screw-capped plastic urine container. Record total volume on container label.

**Patients should not eat avocados, bananas, butternut, cantaloupe, dates, eggplant, grapefruit, hickory nuts, honeydew, kiwi fruit, melons, nuts, pecans, pineapple, plums, tomatoes, or walnuts for a 48 hour period prior to start and duration of collection. Could result in falsely elevated 5-HIAA excretion. Medications affecting metabolism of serotonin must be avoided at least 72 hours before and during collection. Patients should also avoid coffee, tea, and tobacco. Patient should consult their physician before discontinuing any medications.