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5-HTP supplement: what it does and who should avoid it

By the Life in Good Form editors. Updated 2026-10-15.

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What 5-HTP is

A 2020 review in the International Journal of Molecular Sciences explains that the body makes 5-HTP from tryptophan, then turns it into serotonin, which in turn becomes melatonin. Making 5-HTP is the limiting step in serotonin and melatonin production.

5-HTP is both a drug and a dietary supplement ingredient. Seeds of Griffonia simplicifolia are the main commercial source, because chemical synthesis is not economical on a large scale. NOW Foods' 5-HTP, for example, lists 100 mg of 5-HTP from Griffonia seed extract.

What the research shows

Depression. Early studies explored 5-HTP as an antidepressant with relatively few side effects. But a 2012 review in Neuropsychiatric Disease and Treatment states that many promoters make exaggerated and inaccurate claims about depression that the science does not support, and that 5-HTP may be contraindicated for some of the very patients it is promoted to.

Sleep. In normal subjects, 5-HTP increased REM sleep from 5% to 53% of placebo baseline, depending on dose. It was also used in children with sleep terrors.

Migraine and fibromyalgia. The 2020 review describes 5-HTP as studied for migraine prevention, with fewer days with headache after two weeks in one study, and improved clinical measures in 50 people with primary fibromyalgia, with only mild, short-lived side effects.

Other findings. The 2020 review notes evidence that transport of 5-HTP across the blood-brain barrier is impaired in major depression, which may limit how much reaches the brain in the people most likely to try it. It also describes partial improvement in coordination with long-term 5-HTP in cerebellar ataxia, though effects were sometimes incomplete. These are small, older studies, not proof of benefit.

Serotonin syndrome and antidepressants

Too much serotonin can cause serotonin syndrome, which the 2020 review describes as a triad of altered mental status, unstable body functions such as heart rate and temperature, and muscle abnormalities. It usually results from antidepressant medicines and can be fatal, though supportive care usually brings full recovery.

Because 5-HTP is a direct serotonin precursor, NOW Foods' label says to consult a physician if you take medications, especially antidepressants. Do not combine 5-HTP with SSRIs or other serotonin-raising drugs unless your doctor directs it.

Other side effects and purity

• Stomach upset. 5-HTP can cause dose-dependent digestive problems, and nausea and vomiting have been reported above 100 mg. NOW Foods notes mild, transient GI symptoms and suggests taking it with food if they occur.
• Drowsiness. NOW Foods warns it may cause drowsiness and suggests taking it at bedtime.
• Anxiety with certain drugs. Combining 5-HTP with a peripheral decarboxylase inhibitor may cause acute anxiety.
• Contaminants. Contaminated L-tryptophan caused eosinophilia-myalgia syndrome (EMS) in 1989. Studies have found a contaminant called peak X in some commercial 5-HTP samples, though no definitive toxicity cases have emerged apart from one unresolved case.
• Pregnancy. NOW Foods says 5-HTP is not recommended for pregnant or nursing women.

How to choose a 5-HTP supplement

• Talk with your doctor first, especially if you take antidepressants or have depression.
• Start low. NOW Foods' 100 mg capsule is taken once daily, preferably on an empty stomach at bedtime; NOW Foods also sells 50 mg and 200 mg Double Strength versions.
• Source and testing. Look for Griffonia seed extract and brands that state purity testing, given past contaminant findings.
• Avoid stacking. Mood blends often add L-tryptophan, GABA or L-theanine. Tryptophan is the building block the body uses to make 5-HTP.
• Not a depression treatment. See a professional for depression rather than self-treating.

What to look for when you buy

Questions people ask

What is 5-HTP supplement used for?

It has been studied for depression, sleep, migraine and fibromyalgia. Evidence is limited, and one review says depression claims are exaggerated.

Can I take 5-HTP with antidepressants?

Not without your doctor's advice. Both raise serotonin, and too much can cause serotonin syndrome.

When should I take 5-HTP?

Follow the label. NOW Foods suggests once daily, preferably on an empty stomach at bedtime, with food if stomach upset occurs.

What are 5-HTP side effects?

Stomach upset, nausea, vomiting at higher doses, and drowsiness.

Is 5-HTP safe in pregnancy?

No. NOW Foods says it is not recommended for pregnant or nursing women.

Sources

• 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology (pmc.ncbi.nlm.nih.gov), International Journal of Molecular Sciences (PMC7796270)
• 5-HTP efficacy and contraindications (pmc.ncbi.nlm.nih.gov), Neuropsychiatric Disease and Treatment (PMC3415362)
• 5-HTP 100 mg Veg Capsules (www.nowfoods.com/products/supplements/5-htp-100-mg-veg-capsule), NOW Foods

Sources checked 2026-10-15.