What is this test?
This test measures serotonin in blood. It is an adjunct, not a stand-alone test, when evaluating or monitoring serotonin-producing neuroendocrine (carcinoid) tumours; it is not a laboratory test for depression, anxiety, or mood.
Why might it be ordered?
- For symptoms such as episodic flushing and diarrhoea when a clinician considers carcinoid syndrome in the differential diagnosis.
- As an adjunct to more appropriate initial tests, such as 24-hour urinary 5-HIAA or chromogranin A, when clinically indicated.
- For monitoring an established or treated serotonin-producing tumour.
What sample is needed?
The catalogue specifies venous blood. The exact material, such as serum or whole blood, and its processing are method-dependent and must be confirmed with the laboratory.
How should you prepare?
Some medicines, including certain antidepressants and lithium, can change the value. Do not stop anything on your own; provide a full medicines list and follow the laboratory instructions about food and timing.
How should you understand the result?
The concentration is compared with the interval for the specific method. A high value may support a wider assessment but does not prove a tumour, and a normal value does not exclude every neuroendocrine tumour.
Sources and editorial status
This patient-facing text is an editorial draft. It should be approved by a laboratory physician before official publication.