Low 5-HIAA (5-hydroxyindoleacetic acid): what it means
A 5-HIAA (5-hydroxyindoleacetic acid) result below the normal range is considered low. Here is what a reduced 5-HIAA (5-hydroxyindoleacetic acid) can point to, and when it is worth discussing with a doctor.
Reference range: 24-hour urine ~2–8 mg/day; a high level suggests a serotonin-producing carcinoid tumour — but many foods and drugs must be avoided beforehand to avoid false results
Understand your full resultWhat a low 5-HIAA (5-hydroxyindoleacetic acid) can mean
- Normal or low — the expected result; makes an active serotonin-producing carcinoid tumour unlikely.
- A falling level during treatment — can indicate the tumour is responding.
When to discuss with a doctor
Urinary 5-HIAA is a targeted specialist test, ordered mainly when carcinoid syndrome is suspected — for example unexplained flushing with diarrhoea — or to monitor a known carcinoid tumour. Its accuracy depends heavily on preparation: the serotonin-rich foods and interfering medicines must be avoided as instructed for a few days before and during the 24-hour urine collection, or the result can be falsely high. A genuinely raised level, interpreted with chromogranin A and imaging, points toward a carcinoid tumour that needs specialist management. Mediora.AI can surface a raised 5-HIAA from your results and flag the carcinoid pattern for review, but confirming the diagnosis and its treatment is a specialist assessment — the interpretation belongs with your doctor.
Conditions this can relate to
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Upload your test - freeMediora.AI is informational - interpretation, not a diagnosis. A single out-of-range value is common and often benign; always discuss decisions with your doctor.