Lab Test

Serotonin, Serum

Test Codes



Send Outs


This assay is NOT a Serotonin Release Assay (used for the diagnosis of heparin-induced thrombocytopenia).

Specimen Collection Criteria

Collect (preferred specimen): One plain Red-top tube.
Also acceptable: One Gold-top SST tube.

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and refrigerate.

Preparation for Courier Transport

Transport: 2.5 mL serum, refrigerated.

Rejection Criteria

Specimens not collected or processed as indicated.

In-Lab Processing

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and refrigerate.

Transport: 2.5 mL serum, refrigerated. 


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 4 days
Refrigerated (2-8°C or 36-46°F): 21 days
Frozen (-20°C/-4°F or below): 90 days

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.


Sent to Mayo Medical Laboratories, Rochester, MN.


Monday, Wednesday, Friday.
Results available in 5-7 days.

Reference Range

Less than or equal to 230 ng/mL.

Test Methodology

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).


Medication which may affect seratonin concentrations include lithium, MAO inhibitors, methyldopa, morphine, and reserpine. In general, serotonin-containing foods do not interfere significantly. Slight increases may be seen in acute intestinal obstruction, acute MI, cystic fibrosis, dumping syndromes, and nontropical sprue. Metastasizing abdominal carcinoid tumors often show serotonin values greater than 400 ng/mL.

Note: In general, EDTA whole blood (as compared to serum) transported with ascorbic acid preservative will give values most representative of blood concentrations. 95% of blood serotonin is typically found in platelets.

Clinical Utility

Serotonin (5-hydroxytryptamine) is derived from tryptophan and is carried in blood by platelets. This smooth muscle stimulant is oxidatively deaminated to 5-hydroxyindoleacetic acid (5-HIAA).

Increased serotonin levels have been seen in carcinoid syndrome, migraine, schizophrenic, essential hypertension, Huntington's disease, and Duchenne's muscular dystrophy. In carcinoid tumors , the serotonin is variably metabolized to 5-HIAA, depending upon the tissue of origin. The majority of patients usually have very high levels of urinary 5-HIAA.

CPT Codes

LOINC:  27057-9


Last Updated


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