What does the Serotonin test measure?

Why is Serotonin measured?

Urine serotonin is used in functional testing to explore mood, sleep, and gastrointestinal complaints, though its predominantly peripheral origin limits direct inference about brain serotonergic activity. Marked elevation raises suspicion for carcinoid tumours, which require plasma or 24-hour urine 5-HIAA for definitive work-up. Functional interpretations must distinguish peripheral from central contributions.

Reference ranges

Standard reference

Method-specific; clinical laboratories prefer 24-hour collections for carcinoid screening.

Functional medicine optimal

Functional practitioners may favour ranges tighter than laboratory limits, but these intervals are not validated in controlled trials and should be treated as hypothesis-generating.

Units

µg/g creatinine, nmol/mmol creatinine, µg/24 hr, nmol/24 hr, ng/mg creatinine, μg/g creatinine

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.