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.
5-HT level; 5-hydroxytryptamine level; Serotonin test
How the test is performed
Blood is most often drawn from a vein. The vein usually used is on the inside of the elbow or the back of the hand.
The procedure is done in the following way:
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.
A needle is gently inserted into the vein.
The blood collects into an airtight vial or tube attached to the needle.
The elastic band is removed.
The needle is removed.
The puncture site is covered with an adhesive strip to stop any bleeding.
For infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. Afterward, a bandage may be placed over the area if there is any bleeding.
How to prepare for the test
No special preparation is needed.
How the test will feel
When the needle is inserted to draw blood, you may feel slight pain, or only a prick or stinging. Afterward, there may be some throbbing.
Why the test is performed
This test may be done to diagnose carcinoid syndrome. Many patients with carcinoid syndrome have high levels of serotonin in blood and urine.
The normal range is 101-283 nanograms per milliliter (ng/mL).
Note: Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.
What abnormal results mean
A higher-than-normal level may indicate carcinoid syndrome.
What the risks are
There is very little risk in having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks may include:
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Salwen MJ, Siddiqi HA, Gress FG, Bowne WB. Laboratory diagnosis of gastrointestinal and pancreatic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 22.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.