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Serum Serotonin Test – 5-hydroxytryptamine level

5-HT level; 5-hydroxytryptamine level; Serotonin test

The serotonin test measures the level of serotonin in the blood.

The serotonin test measures the level of serotonin in the blood. Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

No special preparation is needed.

How the Test will Feel

When the needle is inserted to draw blood, some people feel slight pain. Others feel a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

Serotonin is a chemical produced by nerve cells.

This test may be done to diagnose carcinoid syndrome. Carcinoid syndrome is a group of symptoms associated with carcinoid tumors. These are tumors of the small intestine, colon, appendix, and bronchial tubes in the lungs. People with carcinoid syndrome often have high levels of serotonin in the blood.

Normal Results

The normal range is 101 to 283 ng/mL.

Note: Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. 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.

Risks

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:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

FAQ

What is a normal serotonin serum level?

  • Generally, the normal range for serotonin levels in your blood is 101–283 nanograms per milliliter (ng/mL). This benchmark, however, may differ slightly depending on the measurements and samples tested, so talk to your doctor about specific test results. High levels of serotonin may be a sign of carcinoid syndrome.

What does low serum serotonin mean?

  • People who feel unusually irritable or down for no apparent reason may have low serotonin levels. Depression: Feelings of sadness, hopelessness, and anger, as well as chronic fatigue and thoughts of suicide, may indicate depression. Anxiety: Low serotonin levels may cause anxiety.

What is a serotonin blood test called?

  • The main test for carcinoid syndrome measures a substance called 5-HIAA in the urine. When a tumor makes serotonin, your body turns it into 5-HIAA. This test may require collecting all the urine you make over a 24-hour period. Another test measures a substance called chromogranin A in your blood.

Can you test for serotonin levels?

  • No single test can confirm a serotonin syndrome diagnosis. Your doctor will diagnose the condition by ruling out other possibilities. Your doctor will likely begin by asking about your symptoms, medical history, and any medications you’re taking. Your doctor will also conduct a physical examination.

What are the signs of low serotonin levels?

Some common signs of serotonin deficiency include:

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

Add references, clinical guidelines, textbooks, journal articles, or trusted medical sources here. You can edit this area later with a custom field named _rx_references.

Written by Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist

Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices. Born and educated in Bangladesh, Dr. Rashid earned his BPT from the University of Dhaka before pursuing postgraduate training internationally. He completed his MD in Internal Medicine at King’s College London, where he developed a special interest in inflammatory arthritis and metabolic bone disease. He then undertook a PhD in Orthopedic Science at the University of Oxford, conducting pioneering research on cytokine signaling pathways in rheumatoid arthritis. Following his doctoral studies, Dr. Rashid returned to clinical work with a fellowship in interventional pain management at the Rx University School of Medicine, refining his skills in image-guided joint injections and minimally invasive pain-relief techniques.