The serotonin test measures the level of serotonin in the blood. Serotonin is a chemical produced by nerve cells. The serum serotonin level is a blood test to measure the amount of serotonin in your body.
Learn about the serotonin test, which may be used in combination with a 5-HIAA test to help diagnose carcinoid tumors.
Also Known as: Serotonin, Serotoninergic, 5-Hydroxytryptamine, 5-HT

How the test is performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Normal Values:
The normal range is 50 to 200 ng/mL (0.28 to 1.14 µmol/L).
Increase Serotonin levels in
- Increased Serotonin synthesis: L-Tryptophan
- Decrease Serotonin metabolism: MAO inhibitors
- Increase Serotonin release: Amphetamines, Cocaine
- Inhibit Serotonin uptake
- Tricyclic Antidepressants: Amitriptyline
- Selective Serotonin Reuptake Inhibitor (SSRI): Prozac
- Other: Meperidine, Dextromethorphan
- Direct Serotonin Receptor Agonists: Buspar, Imitrex
- Dopamine Agonists: Amantadine, Wellbutrin, Levodopa
- Other Non-specific Serotonin increase: Lithium
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