5-HTP

5-HTP at a Glance

5-HTP (5-hydroxytryptophan) is the intermediate between the amino acid tryptophan and serotonin, extracted commercially from the seeds of the African shrub Griffonia simplicifolia.

What makes it useful is that it bypasses the rate-limiting step in serotonin synthesis. Tryptophan has to pass through tryptophan hydroxylase, which is tightly regulated; 5-HTP is already past it and crosses into the brain freely, so it raises serotonin far more directly.

What It’s Used For

• Depression & low mood — its most-studied use, raising serotonin for mood.
• Sleep & insomnia — serotonin is the precursor to melatonin, which is the route here.
• Appetite & weight loss — increases satiety.
• Migraine & headache — used in migraine prophylaxis.
• Fibromyalgia — for pain and sleep in fibromyalgia.
• Cognitive function — studied alongside the mood work.

How It Works

Tryptophan → 5-HTP → serotonin is a two-step path, and the first step is the bottleneck. Supplying 5-HTP skips it, so conversion depends only on aromatic L-amino acid decarboxylase, which is abundant and unregulated.

That enzyme works throughout the body, so a good share of an oral dose becomes serotonin peripherally, in the gut. This is why 5-HTP is paired with a peripheral decarboxylase inhibitor in research settings, and why doses are started low and taken with food.

The full trial record is in Pharmacology & Research below.

Pharmacology & Research

5-HTP (5-hydroxy-L-tryptophan, oxitriptan) is a non-proteinogenic amino acid that sits one enzymatic step downstream of tryptophan and one step upstream of serotonin. Because it bypasses tryptophan hydroxylase — the rate-limiting enzyme in serotonin synthesis — and is not diverted into protein or niacin, oral 5-HTP raises central serotonin more reliably than tryptophan does ^{1,10Reference 1Maffei · 2020ReviewMaffei, M. E. (2020). 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology — review. Int J Mol Sci. https://pubmed.ncbi.nlm.nih.gov/33375373/View study →Reference 10Birdsall · 1998ReviewBirdsall, T. C. (1998). 5-Hydroxytryptophan: a clinically-effective serotonin precursor — review. Altern Med Rev. https://pubmed.ncbi.nlm.nih.gov/9727088/View study →}.

The evidence posture is best described as promising but thin: several small randomized trials point the right way for mood, appetite and fibromyalgia, but almost none are large, independently replicated, or long. Unlike a vitamin or mineral, 5-HTP corrects no dietary deficiency — it is a pharmacologically active serotonergic agent taken on top of a normal diet, so the relevant question is efficacy and safety, not repletion. Two practical caveats dominate: nausea is dose-limiting, and 5-HTP must never be combined with SSRIs, SNRIs, MAOIs, triptans or other serotonergic drugs because of serotonin-syndrome risk.

Evidence by IndicationStrength of support · Beta

Support is an experimental score I’m building — a composite weighted by study type (human > animal > in vitro > review) and study volume. It’s a beta: a fast way to rank strength of evidence at a glance, not a validated metric. Each application links down to its write-up.

01Depression & low moodPromising58%Cochrane review of 2 small RCTs (OR 4.10) + a 2025 RCT; quality-limited ^{2,7Reference 2Shaw et al. · 2002Systematic reviewTryptophan and 5-hydroxytryptophan for depression — systematic review (Cochrane)View study →Reference 7Li et al. · 2025RCTThe Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults — randomised controlled trialView study →}

02Appetite & weight lossPromising52%Small double-blind trials in obese women (900 mg/d), mostly one lab ^{3,4Reference 3Cangiano et al. · 1992RCTEating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan — randomised controlled trialView study →Reference 4Cangiano et al. · 1991RCTEffects of 5-hydroxytryptophan on eating behavior and adherence to dietary prescriptions in obese adult subjects — randomised controlled trialView study →}

03FibromyalgiaPromising48%One 50-patient double-blind trial; older, unreplicated ^{5Reference 5Caruso et al. · 1990RCTDouble-blind study of 5-hydroxytryptophan versus placebo in the treatment of primary fibromyalgia syndrome — randomised controlled trialView study →}

04Migraine & headacheShaky42%Dated prophylaxis trials; mixed, weak modern evidence ^{14Reference 14Yoon et al. · 2005ReviewEvidence-based medicine in migraine prevention — reviewView study →}

05Sleep & insomniaShaky38%Mechanistic (serotonin→melatonin); little direct RCT data ^{1,10Reference 1Maffei · 2020ReviewMaffei, M. E. (2020). 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology — review. Int J Mol Sci. https://pubmed.ncbi.nlm.nih.gov/33375373/View study →Reference 10Birdsall · 1998ReviewBirdsall, T. C. (1998). 5-Hydroxytryptophan: a clinically-effective serotonin precursor — review. Altern Med Rev. https://pubmed.ncbi.nlm.nih.gov/9727088/View study →}

06Cognitive functionShaky32%Single 30-person single-blind RCT in older adults ^{7Reference 7Li et al. · 2025RCTThe Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults — randomised controlled trialView study →}

Mechanisms

Pharmacokinetics

5-HTP is well absorbed orally — roughly 70% reaches the bloodstream — and absorption does not depend on an amino-acid transporter, so it can be taken with food without losing effect ^{10Reference 10Birdsall · 1998ReviewBirdsall, T. C. (1998). 5-Hydroxytryptophan: a clinically-effective serotonin precursor — review. Altern Med Rev. https://pubmed.ncbi.nlm.nih.gov/9727088/View study →}. It crosses the blood–brain barrier freely. The plasma half-life is short, on the order of ~2–4 hours, and pharmacokinetics follow a one-compartment model with a mean oral clearance near 28 L/h and substantial between-person variability ^{11Reference 11Smarius et al. · 2008RCTPharmacology of rising oral doses of 5-hydroxytryptophan with carbidopa — randomised crossover trialView study →}. Much of an oral dose is decarboxylated to serotonin in the periphery before reaching the brain; co-administering a peripheral decarboxylase inhibitor (carbidopa) raises central delivery and cuts nausea, and is standard in research challenge tests ^{11Reference 11Smarius et al. · 2008RCTPharmacology of rising oral doses of 5-hydroxytryptophan with carbidopa — randomised crossover trialView study →}. Because peripheral conversion drives GI side effects, dropout climbs steeply with dose — roughly 7% at 100 mg but ~46% at 300 mg in one challenge study ^{11Reference 11Smarius et al. · 2008RCTPharmacology of rising oral doses of 5-hydroxytryptophan with carbidopa — randomised crossover trialView study →} — which is the practical case for starting low, splitting doses, and taking with food.

Clinical trials

A ClinicalTrials.gov search on the intervention “5-hydroxytryptophan / 5-HTP” returns 42 registered studies, mostly small and investigator-initiated; as an old, off-patent, low-cost molecule, 5-HTP attracts little industry-funded trial investment, and no large phase-III program exists. Recent registered work includes mood/cognition and body-composition trials.

Counts from ClinicalTrials.gov intervention search; last checked: July 2026.

Dietary Sources

5-HTP is an intermediate metabolite, not a dietary nutrient, so it is essentially absent from food in meaningful amounts — the body makes its own from tryptophan, and there is no “eat more of X to get 5-HTP” analogue. What food can supply is its precursor, tryptophan, found in protein-rich foods (poultry, eggs, dairy, fish, soy, nuts and seeds), but dietary tryptophan is heavily diverted into protein synthesis and the kynurenine pathway, and only a small fraction becomes serotonin.

The one notable natural source of 5-HTP itself is the seed of the West African legume Griffonia simplicifolia, whose seeds contain roughly 1–3% 5-HTP by weight — this is where nearly all commercial supplement material is extracted from ^{1Reference 1Maffei · 2020ReviewMaffei, M. E. (2020). 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology — review. Int J Mol Sci. https://pubmed.ncbi.nlm.nih.gov/33375373/View study →}. Some 5-HTP is also produced by chemical or enzymatic/microbial synthesis. Because 5-HTP is not obtainable from a normal diet, supplementation is the only practical way to raise intake, which is precisely why it is sold as a supplement rather than recommended as a food component.

Dosage

These are doses studied in research, not a personal recommendation. 5-HTP is not an essential nutrient, so there is no RDA/AI and no established Tolerable Upper Intake Level.

• Typical supplemental range: 50–300 mg/day, often divided. Mood and cognition trials have commonly used 100 mg/day ^{7Reference 7Li et al. · 2025RCTThe Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults — randomised controlled trialView study →}, while older appetite/weight trials used much higher doses — up to 900 mg/day — which more often provoke nausea ^{3Reference 3Cangiano et al. · 1992RCTEating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan — randomised controlled trialView study →}.
• Titration: Because peripheral conversion to serotonin drives GI upset, dropout rises sharply with dose (≈7% at 100 mg vs ≈46% at 300 mg in a challenge study) ^{11Reference 11Smarius et al. · 2008RCTPharmacology of rising oral doses of 5-hydroxytryptophan with carbidopa — randomised crossover trialView study →}. Starting low (50–100 mg), splitting doses, and taking with food improves tolerability.
• Timing: For sleep, doses are usually taken in the evening; unlike tryptophan, absorption is not blocked by dietary amino acids, so it can be taken with meals ^{10Reference 10Birdsall · 1998ReviewBirdsall, T. C. (1998). 5-Hydroxytryptophan: a clinically-effective serotonin precursor — review. Altern Med Rev. https://pubmed.ncbi.nlm.nih.gov/9727088/View study →}.
• Cofactors: Vitamin B6 (as pyridoxal-5-phosphate) is the cofactor for the decarboxylation of 5-HTP to serotonin and is often co-supplemented; magnesium is frequently paired for sleep formulas.

Safety

5-HTP is usually well tolerated on its own, but it is an active serotonergic agent — the interaction that matters is with other serotonergic drugs, and it is the one that can actually be dangerous.

Safety at a Glance

⚠️ Moderate toxicityDrug interactionsSedating

• No clear pattern of serious organ toxicity. Decades of widespread use at typical supplemental doses.
• Serotonin syndrome is the key interaction. SSRIs, SNRIs, MAOIs, tricyclics, triptans, tramadol, dextromethorphan and St John’s Wort should not be combined with it unsupervized.
• Not for pregnancy or breastfeeding without supervision. See the box below.
• Nausea is dose-limiting. GI upset is dose-dependent and the main reason people stop; drowsiness can also occur.
• Stop before scheduled surgery. Serotonergic interactions with some anesthetic agents.
• Buy from tested sources. Trace “Peak X” contaminants have been found in some commercial samples, though no EMS epidemic has been attributed to 5-HTP.

Full Safety & Interactions Detail

At typical supplemental doses 5-HTP is usually well tolerated, and decades of widespread use have produced no clear pattern of serious organ toxicity ^{9Reference 9Das et al. · 2004ReviewSafety of 5-hydroxy-L-tryptophan — reviewView study →}. The most common adverse effects are gastrointestinal — nausea, and less often vomiting, diarrhea and abdominal discomfort — which are dose-dependent and are the main reason people stop ^{11Reference 11Smarius et al. · 2008RCTPharmacology of rising oral doses of 5-hydroxytryptophan with carbidopa — randomised crossover trialView study →}. Drowsiness can also occur.

• Serotonin syndrome (the key interaction): 5-HTP raises serotonin, so combining it with SSRIs, SNRIs, MAOIs, tricyclics, triptans, tramadol, dextromethorphan, St John’s Wort or other serotonergic agents can cause potentially dangerous serotonin excess (agitation, tremor, hyperthermia, autonomic instability). These combinations should be avoided unless supervised by a clinician.
• Peri-operative caution: Because of serotonergic interactions with some anesthetic agents, 5-HTP is generally stopped before scheduled surgery.
• The EMS / “Peak X” question: In 1989 an epidemic of eosinophilia-myalgia syndrome (EMS) was traced to a contaminated batch of synthetic L-tryptophan from a single manufacturer — not to tryptophan itself. Trace contaminants (“Peak X”) have subsequently been detected in some commercial 5-HTP samples, raising theoretical concern ^{12,13Reference 12Klarskov et al. · 2003Structural characterization of a case-implicated contaminant, “Peak X,” in commercial preparations of 5-hydroxytryptophanView study →Reference 13Klarskov et al. · 1999Eosinophilia-myalgia syndrome case-associated contaminants in commercially available 5-hydroxytryptophanView study →}. However, no confirmed EMS epidemic has been attributed to 5-HTP despite decades of use, and detailed safety analyses have found the contaminant levels to be minute and of doubtful clinical significance ^{9Reference 9Das et al. · 2004ReviewSafety of 5-hydroxy-L-tryptophan — reviewView study →}. The prudent reading: buy from reputable, tested sources, but the historical alarm is largely a tryptophan story, not a 5-HTP one.

Pregnancy & Lactation

⚠ Avoid in pregnancy⚠ Avoid while breastfeeding

Verdict: avoid unless directed by a clinician. There is insufficient safety data on 5-HTP in pregnancy or breastfeeding, and its serotonergic activity plus theoretical contaminant concerns make caution the responsible default. This should not be used during pregnancy or lactation without medical supervision.

References

1. Maffei, M. E. (2020). 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology — review. Int J Mol Sci. https://pubmed.ncbi.nlm.nih.gov/33375373/
2. Shaw, K., Turner, J., & Del Mar, C. (2002). Tryptophan and 5-hydroxytryptophan for depression — systematic review (Cochrane). Cochrane Database Syst Rev. https://pubmed.ncbi.nlm.nih.gov/11869656/
3. Cangiano, C., et al. (1992). Eating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan — randomised controlled trial. Am J Clin Nutr. https://pubmed.ncbi.nlm.nih.gov/1384305/
4. Cangiano, C., et al. (1991). Effects of 5-hydroxytryptophan on eating behavior and adherence to dietary prescriptions in obese adult subjects — randomised controlled trial. Adv Exp Med Biol. https://pubmed.ncbi.nlm.nih.gov/1722953/
5. Caruso, I., Sarzi Puttini, P., Cazzola, M., & Azzolini, V. (1990). Double-blind study of 5-hydroxytryptophan versus placebo in the treatment of primary fibromyalgia syndrome — randomised controlled trial. J Int Med Res. https://pubmed.ncbi.nlm.nih.gov/2193835/
6. Pöldinger, W., Calanchini, B., & Schwarz, W. (1991). A functional-dimensional approach to depression: serotonin deficiency as a target syndrome in a comparison of 5-hydroxytryptophan and fluvoxamine — randomised trial. Psychopathology. https://pubmed.ncbi.nlm.nih.gov/1909444/
7. Li, S., Sutanto, C. N., Xia, X., & Kim, J. E. (2025). The Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults — randomised controlled trial. Nutrients. https://pubmed.ncbi.nlm.nih.gov/40944161/
8. Truyens, M., et al. (2022). Effect of 5-Hydroxytryptophan on Fatigue in Quiescent Inflammatory Bowel Disease — multicentre randomised controlled trial. Gastroenterology. https://pubmed.ncbi.nlm.nih.gov/35940251/
9. Das, Y. T., Bagchi, M., Bagchi, D., & Preuss, H. G. (2004). Safety of 5-hydroxy-L-tryptophan — review. Toxicol Lett. https://pubmed.ncbi.nlm.nih.gov/15068828/
10. Birdsall, T. C. (1998). 5-Hydroxytryptophan: a clinically-effective serotonin precursor — review. Altern Med Rev. https://pubmed.ncbi.nlm.nih.gov/9727088/
11. Smarius, L. J., et al. (2008). Pharmacology of rising oral doses of 5-hydroxytryptophan with carbidopa — randomised crossover trial. J Psychopharmacol. https://pubmed.ncbi.nlm.nih.gov/18308795/
12. Klarskov, K., Johnson, K. L., Benson, L. M., et al. (2003). Structural characterization of a case-implicated contaminant, “Peak X,” in commercial preparations of 5-hydroxytryptophan. J Rheumatol. https://pubmed.ncbi.nlm.nih.gov/12508395/
13. Klarskov, K., Johnson, K. L., Benson, L. M., et al. (1999). Eosinophilia-myalgia syndrome case-associated contaminants in commercially available 5-hydroxytryptophan. Adv Exp Med Biol. https://pubmed.ncbi.nlm.nih.gov/10721089/
14. Yoon, M. S., Savidou, I., Diener, H. C., & Limmroth, V. (2005). Evidence-based medicine in migraine prevention — review. Expert Rev Neurother. https://pubmed.ncbi.nlm.nih.gov/15938666/
15. Ioannou, S., Williams, A. L., et al. (2017). Preliminary fMRI findings concerning the influence of 5-HTP on food selection. Brain Behav. https://pubmed.ncbi.nlm.nih.gov/28127513/
16. Thorpe, J., et al. (2018). Combination pharmacotherapy for the treatment of fibromyalgia in adults — systematic review (Cochrane). Cochrane Database Syst Rev. https://pubmed.ncbi.nlm.nih.gov/29457627/
17. Victor, S., & Ryan, S. W. (2003). Drugs for preventing migraine headaches in children — systematic review (Cochrane). Cochrane Database Syst Rev. https://pubmed.ncbi.nlm.nih.gov/14583952/

View all 17 references▾