• Where is serotonin primarily stored in the blood?

Approximately 95% of the serotonin in the body is stored in blood platelets.

• What factors can trigger the flushing episodes associated with carcinoid syndrome?

Severe flushing of the face and neck is often triggered by emotions, alcohol, or certain types of food.

Medical Laboratories

Whole Blood Serotonin Test

Serotonin, Whole Blood Test

Experiencing unexplained flushing or palpitations? This test helps diagnose hormone-secreting tumors in the digestive tract by accurately measuring serotonin levels, guiding you toward the right medical care.

Trusted medical contentUpdated: 04-09-2026Views: 11LHL-1078

About this service

A whole blood serotonin test is a quantitative measurement of the concentration of the neurotransmitter and hormone serotonin (5-hydroxytryptamine - 5-HT) in whole blood. Approximately 95% of the body's serotonin is stored in platelets (found in whole blood), while the remainder is free in plasma. A significantly elevated serotonin level is an important indicator of a carcinoid tumor, a rare type of neuroendocrine tumor that secretes serotonin and other amines.

Conditions and notices

Fasting is not required

Strict fasting is not required, but fasting for 8-12 hours is preferred for more consistent results.

The doctor should be informed of all medications and supplements the patient is taking, especially antidepressants (SSRIs, MAOIs), migraine medications (triptans), and diuretics, as many of these affect serotonin levels. The doctor may ask the patient to stop taking some of these medications a few days before the examination.

It is preferable to avoid foods rich in serotonin (bananas, pineapple, walnuts, avocados, tomatoes, eggplant) 24-48 hours before the test.

Frequently Asked Questions

Short answers to the FAQs published with this service.

• Who is the target group for this serotonin test?

Target groups include patients with symptoms of carcinoid syndrome (like flushing or watery diarrhea), individuals with known carcinoid tumors for follow-up, and those with unexplained abdominal masses or liver issues.

• Does the whole blood serotonin test require fasting?

No, fasting is not required for this laboratory blood analysis.

• How is this test used to monitor treatment response?

In patients with known carcinoid tumors, a decrease in the level of serotonin in the blood indicates a good response to treatments such as surgery or medication.

• What symptoms might necessitate this procedure?

Whole Blood Serotonin Test

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