Serotonin, Serum

Serotonin, Serum

What it is

The Serotonin, Serum test measures the amount of serotonin in the blood. Serotonin is a neurotransmitter and hormone that plays a key role in mood regulation, digestion, sleep, and other bodily functions. Abnormal serotonin levels may be linked to mood disorders, gastrointestinal conditions, and certain rare tumors such as carcinoid tumors.

Uses

This test is used to:

• Help detect and monitor carcinoid tumors that secrete serotonin.
• Evaluate unexplained flushing, diarrhea, and wheezing (symptoms of carcinoid syndrome).
• Support diagnosis of serotonin-related metabolic or neuroendocrine disorders.
• Assist in differential diagnosis of gastrointestinal and endocrine symptoms.

Symptoms / Conditions That May Lead to the Test

Doctors may recommend this test if you have:

• Persistent diarrhea without clear cause.
• Skin flushing or redness not related to allergies.
• Unexplained wheezing or breathing difficulties.
• Rapid heartbeat or palpitations.
• Abdominal cramps, nausea, or unexplained weight loss.

Abnormal Results

• High Serotonin Levels: May indicate the presence of carcinoid tumors, especially if accompanied by carcinoid syndrome symptoms. Can also be influenced by certain foods (bananas, walnuts, avocados) or medications.
• Low Serotonin Levels: Rarely tested for clinically in serum but may be associated with mood disorders, digestive problems, or other conditions affecting serotonin regulation.

Further confirmatory tests such as urinary 5-HIAA (5-hydroxyindoleacetic acid) or imaging may be ordered if serotonin levels are abnormal.

Risks

The test requires a routine blood sample. Risks are minimal and may include:

• Mild pain or discomfort at the needle site.
• Minor bruising or bleeding.
• Rare dizziness or fainting after the blood draw.