Test Directory

Serotonin measurement is used in conjunction with urinary 5-hydroxyindoleacetic acid (5-HIAA) and/or serum chromogranin A in the diagnosis of carcinoid syndrome.

Specimen Type: Serum

Collection Container: Gold Top, Serum Separator

Alternate Collection Container: Red Top, Plain

Desired Specimen Volume: 1 mL

1. Collect specimen in gold top, serum separator tube via venipuncture.

1. Separate serum from cells within 30 minutes of collection.
2. Transfer 1 mL of serum to a clear aliquot tube (screw cap).

Monoamine oxidase inhibitor drugs should be discontinued for at least one week prior to sampling since they tend to increase the level of serotonin.

Transport to the laboratory refrigerated. 

• Plasma sample received
• Serum that is not separated from cells

See patient report.

The majority of gastroenteropancreatic neuroendocrine, carcinoid tumors do not produce elevated whole blood or serum serotonin levels. In most cases, 5-hydroxyindoleacetic acid (5-HIAA) and chromogranin A are superior tests for the assessment of carcinoid syndrome. In rare instances, a deficiency of aromatic amino acids decarboxylase in carcinoid tumor cell limits the conversion of 5-HTP into serotonin.

Several medications (lithium, monoamine oxidase inhibitors, methyldopa, morphine, and reserpine) can produce elevation in serotonin concentration. Selective serotonin reuptake inhibitors can cause a reduction in serum and whole blood serotonin levels. Tryptophan-rich food (avocados, bananas, plums, walnuts, pineapple, eggplant, plantain, tomatoes, hickory nuts, kiwi, dates, grapefruit, cantaloupe, and honeydew melon) do not contribute to serum or blood serotonin measurements.

• 5-HT, Serum
• 5-Hydroxytryptamine, Serum