What are the side effects of 5-HTP?

Nausea and GI discomfort (most common, dose-related) Drowsiness: take care with driving or machinery Headache Stop taking it and seek practitioner advice for hardening skin, muscle or joint pain or stiffness, tremor, agitation, confusion or a faster heart rate

Who should avoid 5-HTP?

Taking antidepressants: an explicit Health Canada contraindication Scleroderma Pregnancy or breastfeeding without guidance On carbidopa without practitioner oversight

Amino acid

5-HTP

The immediate serotonin precursor, extracted from Griffonia simplicifolia seed, that crosses into the brain more readily than tryptophan. Small trials suggest benefit for mood and sleep, but quality is low and it carries the same serious serotonin-syndrome interaction with antidepressants. An evening/mood-slot ingredient requiring conservative dosing.

Grade CUpdated October 24, 2026Written and fact-checked in-house against The Evidence Standard. Not a clinical review.

Please note

Educational content, not medical advice. Doses below are ranges used in research, not recommendations. Talk to a qualified clinician before starting any supplement, especially if you take medication, are pregnant, or manage a health condition.

Evidence grade: Evidence: Grade C
Studied dose range: 100–300 mg/day typical (Health Canada: mood 150–300 mg/day; sleep 100–200 mg/day; maximum 300 mg per single dose). Start low and titrate over ~2 weeks to limit nausea.
Time to effect: Mood trials reported change from about 2 weeks, mostly without a placebo group; the one recent sleep trial reported its result at 12 weeks.
Best form: Standardized Griffonia simplicifolia seed extract; divided or enteric dosing reduces nausea.

The short answer

5-HTP (Amino acid) is studied for mood-balance support (conservative) and evening or sleep support. In our conservative reading of the published human research, the evidence is Grade C (limited). 100–300 mg/day typical (Health Canada: mood 150–300 mg/day; sleep 100–200 mg/day; maximum 300 mg per single dose). Start low and titrate over ~2 weeks to limit nausea. Mood trials reported change from about 2 weeks, mostly without a placebo group; the one recent sleep trial reported its result at 12 weeks. A studied dose is what trials used, not a recommended dose.

Full profile

Also known as	5-Hydroxytryptophan, Griffonia simplicifolia extract
Best for	Mood-balance support (conservative) · Evening or sleep support · Fibromyalgia-related discomfort (conservative)
Evidence grade	Grade C · Limited: early or small human trials
Studied dose range	100–300 mg/day typical (Health Canada: mood 150–300 mg/day; sleep 100–200 mg/day; maximum 300 mg per single dose). Start low and titrate over ~2 weeks to limit nausea.
Time to effect	Mood trials reported change from about 2 weeks, mostly without a placebo group; the one recent sleep trial reported its result at 12 weeks.
Best form	Standardized Griffonia simplicifolia seed extract; divided or enteric dosing reduces nausea.

Evidence, honestly graded

Limited. 5-HTP crosses the blood-brain barrier without the transport competition tryptophan faces, and small double-blind trials suggest benefit for mood and for fibromyalgia symptoms (Caruso 1990), but the Cochrane review and a follow-up meta-analysis (Shaw 2001; Shaw 2002) judged the overall evidence insufficient to recommend routine use: the trials are small, old, and largely unreplicated at modern standards. Newer trials don't change that. The largest placebo-controlled trial we found, in 166 adults with fatigue from inactive inflammatory bowel disease, found 100 mg twice daily no better than placebo on fatigue, depression, anxiety or stress after 8 weeks (Truyens 2022), and a 30-person single-blind trial in older adults reported better sleep in poor sleepers at 12 weeks against no treatment rather than a placebo (Sutanto 2024). Graded C, with a prominent drug-interaction caution.

See the full grading rubric (study type, replication, population match, and dose adequacy) in The Evidence Standard.

704 natural health products with an active licence in Health Canada's LNHPD list 5-HTP as a medicinal ingredient.

That makes 5-HTP a recognized, licensable medicinal ingredient in Canada, regulated by Health Canada's Natural and Non-prescription Health Products Directorate, which issues each licensed natural health product a Natural Product Number (NPN). Search the LNHPD to verify.

Source: Health Canada Licensed Natural Health Products Database, snapshot 2026-10-18. A count of products with an active licence, not an endorsement of any health claim. This describes the ingredient's regulatory standing in Canada, not Signal State Core, which is a pre-launch concept and is not a licensed natural health product.

Side effects

Nausea and GI discomfort (most common, dose-related)
Drowsiness: take care with driving or machinery
Headache
Stop taking it and seek practitioner advice for hardening skin, muscle or joint pain or stiffness, tremor, agitation, confusion or a faster heart rate

Who should avoid it or check first

Taking antidepressants: an explicit Health Canada contraindication
Scleroderma
Pregnancy or breastfeeding without guidance
On carbidopa without practitioner oversight

Interactions

Serious serotonin-syndrome risk with SSRIs, SNRIs, MAOIs, triptans, tramadol, dextromethorphan, and other serotonergic agents; this caution must be prominent
Caution with carbidopa; additive sedation with CNS depressants

Stacks well with

Melatonin (evening slot)

Use caution stacking with

Any antidepressant or serotonergic agent
L-Tryptophan (redundant serotonergic precursor)

What to look for on a label

Carry the mandatory "do not use if you are taking antidepressants" warning verbatim.
The dedicated Canadian 5-HTP monograph distinguishes antidepressant and scleroderma contraindications from consultation cautions, and gives driving and stop-use instructions. Confirm the full warning set for the intended use before filing.

References

Shaw K, Turner J, Del Mar C (2001). Cochrane Database of Systematic Reviews, (3):CD003198Systematic review (Cochrane)Signal favoring treatment; evidence insufficient to recommend routine use.
Shaw K, Turner J, Del Mar C (2002). Australian and New Zealand Journal of Psychiatry, 36(4):488–491Meta-analysisBetter than placebo, but low-quality evidence base.
Caruso I, Sarzi Puttini P, Cazzola M, Azzolini V (1990). Journal of International Medical Research, 18(3):201–209Double-blind, placebo-controlledImproved fibromyalgia symptoms versus placebo.
Truyens M, Lobatón T, Ferrante M, et al. (2022). Gastroenterology, 163(5):1294–1305.e3Multicentre randomized, placebo-controlled crossover, n=166 adults with inflammatory bowel disease in remission and fatigue, two 8-week periodsStudied dose: 100 mg twice dailyNo difference from placebo in fatigue (a 20% or greater reduction in 35.6% on 5-HTP vs 37.6% on placebo) or in depression, anxiety and stress scores.
Sutanto CN, Xia X, Heng CW, et al. (2024). Clinical Nutrition, 43(3):593–602Single-blind randomized controlled trial, n=30 adults with a mean age of 66, 12 weeks, versus no supplementStudied dose: 100 mg dailyPoor sleepers improved their global sleep-quality score at week 12; good sleepers did not.
Health Canada: 5-HTP, 28 August 2024. Dedicated monograph gives contraindications, driving caution and concrete stop-use symptoms.

Entries above without a linked identifier are either editorial summaries of a wider body of literature or references to a named authority (a regulator or government monograph) cited by name rather than by a single paper.

Grades and studied doses are our conservative reading of the human research, shown for education. They are not product claims, and a studied dose is not a recommended dose.

Revision history

Every change to this ingredient's evidence status, dated and explained. The full cross-library log lives at Evidence Updates.

2026-10-24Citation review
Added the largest placebo-controlled trial we found: in 166 adults with inactive inflammatory bowel disease, 100 mg twice a day for 8 weeks did no better than placebo on fatigue, depression, anxiety or stress. Also added a small 12-week sleep trial in older adults that had no placebo group. C holds.
2026-10-12Safety note
Added the Canadian monograph's driving caution and the symptoms that mean stop. The antidepressant and scleroderma contraindications are unchanged. C holds.
2026-07-12New profile
New profile at Grade C, with explicit serotonergic-interaction cautions.

See how 5-HTP compares on grade, dose, and goal in the Evidence Explorer.

Less noise. More signal.

Get The Signal by email

New research write-ups, evidence-grade changes and safety notes, about every two weeks. Free, with the Clean Focus Stack Guide when you join, and first word if Signal State Core launches.

About every two weeksFree guide on signupUnsubscribe anytime