Type the milligrams of L-tryptophan in one capsule and how many you take at night. You see where that sits among the doses the placebo-controlled sleep trials gave, the trials that gave about that much, and what each one found — including the ones that found nothing.
Your night
Among the doses the sleep trials gave 1 g a night (500 mg × 2) — the trials gave 0.25 to 6 g
6 trials gave about 1 g (within 10%): 3 reported better sleep, 3 found no difference.
- Hartmann & Spinweber 1979 — 15 mild insomniacs (sleep latency over 30 minutes); ¼ g, ½ g and 1 g, each against a placebo, at bedtime, in a sleep laboratory. At 1 g it reported a better sleep measure than placebo: “One gram of L-tryptophan significantly reduced sleep latency: the lower doses produced a trend in the same direction. Stage IV sleep was significantly increased by 1/4 g of L-tryptophan.”
- Brown et al. 1979 — 18 women whose sleep onset took over 20 minutes; 1 g or 3 g, on 10 nights over 3 months, 20 minutes before lights out. At 1 g it found no difference from placebo: “Neither dose of l-tryptophan differed from placebo as to the amount of REM, SWS or wakefulness, but 3 gms. significantly reduced sleep onset latency on some of the nights.”
- Nicholson & Stone 1979 — 6 healthy men aged 20 to 30; 2, 4 and 6 g at night, and 1, 2 and 4 g before an afternoon sleep, in a sleep laboratory. At 1 g it found no difference from placebo: “It was not possible to establish an effect of L-tryptophan compared with placebo on night-time sleep With 4 g L-tryptophan there was an increase in the duration of stage 3 of day-time sleep compared with placebo. The hypnotic activity of L-tryptophan per se is limited and uncertain.”
- Hartmann, Lindsley & Spinweber 1983 — 96 people with serious insomnia, in separate groups; 1 g nightly for 7 nights, nightly. At 1 g it found no difference from placebo: “During the treatment week, flurazepam produced significant improvement on several sleep measures compared to placebo, while tryptophan and secobarbital did not. Sleep latency was not significantly improved by tryptophan during the treatment week, but continued to improve during the post-treatment week, resulting in a significant difference between tryptophan and baseline in week 2.”
- Wang et al. 2016 — 80 people in residential drug-abstinence treatment (45 finished); 1,000 mg a day for 2 weeks, daily. At 1 g it reported a better sleep measure than placebo: “The reduction in the Athens Insomnia Scale score in the tryptophan group was significantly greater than that in the placebo group (P = 0.017).”
- van Dalfsen & Markus 2019 — 98 adults chosen by a serotonin-transporter gene variant; 1,000 mg a day for 1 week, crossed over with a placebo week, before sleep. At 1 g it reported a better sleep measure than placebo: “Tryptophan improved objective sleep efficiency and objective wake after sleep onset irrespective of allelic variation.”
Of the 14 placebo-controlled sleep trials of L-tryptophan alone we could read (1979–2019, 629 people in all), 7 reported a better sleep measure than placebo — two of them in daytime naps of healthy adults, one only after the third night — 5 found no difference, and 2 had a mixed result.
NCCIH: “Dietary supplements containing substances that can be changed into melatonin in the body—L-tryptophan and 5-hydroxytryptophan (5-HTP)—have sedative effects, but it is unclear how they work and there is very limited data on their effects on insomnia.” “The 2017 clinical practice guideline from the American Academy of Sleep Medicine recommended against using tryptophan for treating chronic insomnia.”
This is not medical advice, and no result here says L-tryptophan will help you sleep. If you take an antidepressant or any medicine that acts on serotonin, ask your doctor or pharmacist first. NCCIH: “There are serious safety concerns about kava products (which have been linked to severe liver damage) and L-tryptophan supplements (which may cause life-threatening serotonin toxicity when used with medicines that affect serotonin metabolism).”
The placebo-controlled sleep trials of L-tryptophan alone gave 0.25 to 6 g, most of them 1 to 3 g at bedtime. Of the 14 we could read, 7 reported a better sleep measure than placebo, 5 found no difference and 2 had mixed results. The NIH’s NCCIH calls the data on insomnia “very limited”. Type your capsule’s milligrams to see which trials gave about your amount.
How to use it
Type the milligrams of L-tryptophan in one capsule (the label’s Supplement Facts) and how many you take at night. The tool adds them up in grams, places that night among every dose the trials gave, and lists the trials that gave about the same — within 10% — with who took it, for how long, and what each found in the trial’s own words. With no trial that close, it names the trials of the nearest dose. It never suggests a dose: the trials are placed, not recommended.
What L-tryptophan is
MedlinePlus: “It is an essential amino acid. This means your body cannot produce it, so you must get it from your diet.” “The body uses tryptophan to help make melatonin and serotonin.” That is why it was tested for sleep: most of the trials ran in sleep laboratories in the 1970s and 1980s, at gram doses far above a capsule of a few hundred milligrams. One 1979 trial put those doses in context: “These results at low doses have interesting implications since the normal dietary intake of L-tryptophan is 1/2 g to 2 g per day.”
What the NIH says
NCCIH, the NIH’s center for complementary health, in its sleep disorders review (last updated May 2024): “Dietary supplements containing substances that can be changed into melatonin in the body—L-tryptophan and 5-hydroxytryptophan (5-HTP)—have sedative effects, but it is unclear how they work and there is very limited data on their effects on insomnia.” “The 2017 clinical practice guideline from the American Academy of Sleep Medicine recommended against using tryptophan for treating chronic insomnia.” And on safety: “There are serious safety concerns about kava products (which have been linked to severe liver damage) and L-tryptophan supplements (which may cause life-threatening serotonin toxicity when used with medicines that affect serotonin metabolism).”
The trials, and what they found
| Trial | Who | Dose | Found |
|---|---|---|---|
| Hartmann & Spinweber 1979 | 15 mild insomniacs | 0.25, 0.5, 1 g | shorter time to sleep at 1 g |
| Brown et al. 1979 | 18 women slow to fall asleep | 1, 3 g | shorter time to sleep at 3 g, on some nights |
| Nicholson & Stone 1979 | 6 healthy men | 1, 2, 4, 6 g | no effect on night-time sleep |
| Linnoila et al. 1980 | 19 older inpatients | 3 g | no difference |
| Hartmann, Lindsley & Spinweber 1983 | 96 people with serious insomnia | 1 g | no difference in the treatment week |
| Spinweber et al. 1983 | 20 healthy adults, daytime nap | 4 g | shorter time to fall asleep in a nap |
| Spinweber 1986 | 20 young men slow to fall asleep | 3 g | shorter time to sleep on nights 4–6, not 1–3 |
| Ferrero & Zahnd 1987 | 21 psychiatric inpatients | 0.25, 0.5 g | no difference |
| Demisch et al. 1987 | 39 people with chronic insomnia | 2 g | mixed: only when the full dose came first |
| George et al. 1989 | 10 healthy volunteers, daytime | 1.2, 2.4 g | shorter time to fall asleep in the daytime |
| Asheychik et al. 1989 | 76 men in alcohol treatment | 3 g | no difference |
| van Dalfsen & Markus 2015 | 111 adults, by a gene variant | 3 g | mixed: better only in one subgroup |
| Wang et al. 2016 | 80 people in drug-abstinence treatment | 1 g | better insomnia score |
| van Dalfsen & Markus 2019 | 98 adults, by a gene variant | 1 g | better sleep efficiency and less waking |
Left out, and why: a 1982 review (quoted below), an analysis of who responded in one trial, a trial with no control group, one that compared patients with their own baseline, one whose abstract gives no sleep result of its own, one that gave tryptophan with carbohydrate and no dose, tryptophan-depletion studies, and blends with melatonin, magnesium or herbs. One trial used no true placebo: “Instead of a placebo, a very low dose of 0.04 g L-TRP was used.”
What the reviews say
A 1982 review of 40 controlled studies, by the author of several of the trials: “Best results (in terms of positive effects on sleep or sleepiness) have been found in subjects with mild insomnia, or in normal subjects reporting a longer-than-average sleep latency.” “Mixed results are also reported in severe insomniacs and in patients with serious medical or psychiatric illness.” A 2022 meta-analysis pooled only a few trials: “Extracted data from 4 articles were also analyzed using random-effect meta-analysis and meta-regression.” “Results from the study suggested that Trp supplementation can shorten wake after sleep onset (-81.03 min/g, P = 0.017; SMD, -1.08 min [95%CI, -1.89 to -0.28]).” “However, Trp supplementation did not affect other sleep components.”
The 1989 recall
L-tryptophan was pulled from US shelves in 1989. The CDC reported: “As of November 21, 360 cases of eosinophilia-myalgia syndrome (EMS) had been reported by state health departments to CDC.” “The case-control studies in New Mexico and Minnesota establish a statistically significant association between use of LTCPs and development of EMS.” “On November 17, the Food and Drug Administration (FDA) announced its intention to seek a nationwide recall of all LTCPs in which LT is the sole or major component; this reinforced a November 11 alert to the public to refrain from using LTCPs.” NCCIH: “The use of L-tryptophan as a dietary supplement was discontinued in 1989 because of an outbreak of eosinophilia-myalgia syndrome (EMS) that was traced to contaminated synthetic L-tryptophan from a single manufacturer.” L-tryptophan is sold as a supplement again today and is not on the FDA’s current import alert list; ask your pharmacist about a brand’s testing.
Antidepressants and serotonin
Tryptophan is named on the FDA-approved label of sertraline (Zoloft), in its warning on serotonin syndrome: “Serotonin-norepinephrine reuptake inhibitors (SNRIs) and selective serotonin reuptake inhibitors (SSRIs), including ZOLOFT, can precipitate serotonin syndrome, a potentially life-threatening condition.” “The risk is increased with concomitant use of other serotonergic drugs (including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, meperidine, methadone, tryptophan, buspirone, amphetamines, and St. John’s Wort) and with drugs that impair metabolism of serotonin, i.e., MAOIs”. This tool does not check medicines: if you take any of these, ask your doctor or pharmacist before L-tryptophan.
Worked examples
- 500 mg × 2 capsules (the page’s example): 1 g, among the trial doses. Six trials gave about 1 g: three reported better sleep, three found no difference — including the largest, 96 people over a week.
- 500 mg × 1: 0.5 g. Two trials gave about that much, and neither found a difference at that dose.
- 1,000 mg × 3: 3 g. Five trials gave about 3 g: two reported better sleep, two found no difference and one had a mixed result.
- 200 mg × 1: 0.2 g, less than any sleep trial gave; the nearest dose, 0.25 g, was in two trials, neither with a clear result at that dose.
Common mistakes
- Confusing L-tryptophan with 5-HTP. 5-HTP is a different compound, sold separately; no trial here gave it.
- Reading a serving as a capsule. If the label’s serving is two capsules, divide its milligrams by two before typing.
- Counting a nap study as a night’s sleep. Two of the trials that found something measured how fast healthy adults fell asleep in the daytime.
- Expecting the first night to count. In one trial the shorter time to sleep appeared only on nights 4 to 6; in another, nothing differed from placebo in the treatment week.
- Taking it with an antidepressant without asking. The sertraline label names tryptophan among the drugs that raise the risk of serotonin syndrome.
Frequently asked questions
Does tryptophan help you sleep?
Of the 14 placebo-controlled trials of L-tryptophan alone we could read, 7 reported a better sleep measure than placebo, 5 found no difference and 2 were mixed. A 2022 meta-analysis found shorter waking during the night, and: “However, Trp supplementation did not affect other sleep components.” NCCIH: “The 2017 clinical practice guideline from the American Academy of Sleep Medicine recommended against using tryptophan for treating chronic insomnia.”
How much L-tryptophan for sleep did the trials give?
From 0.25 g to 6 g, most often 1 g or 3 g at night. This page found no official dose for L-tryptophan as a sleep aid, and the tool does not suggest one.
When did the trials give it?
Mostly at bedtime or 20 minutes before lights out; the 2015–2019 trials gave a daily amount for a week or two. Two tested only daytime sleep, in healthy adults.
Are tryptophan supplements safe to take with antidepressants?
The FDA-approved sertraline label names tryptophan among the drugs that raise the risk of serotonin syndrome, “a potentially life-threatening condition.” Ask your doctor or pharmacist before combining them.
Why was L-tryptophan recalled?
In 1989 it was linked to an epidemic of eosinophilia-myalgia syndrome; the CDC reported 360 cases by November 21, and the FDA sought a nationwide recall of products in which it was the sole or major component.
Is tryptophan the same as 5-HTP?
No — they are different compounds, sold separately, and none of these trials gave 5-HTP. MedlinePlus on tryptophan: “The body uses tryptophan to help make melatonin and serotonin.”
More sleep tools: the Melatonin Dose & Timing Calculator, Glycine for Sleep, Magnesium for Sleep and Chamomile for Sleep.
Read next
- L-Tryptophan
- L-Tryptophan foods: 11 foods high in the amino acid
- Does honey help you sleep?
- Do nootropics affect sleep?
This is not medical advice, and nothing here says L-tryptophan treats insomnia or any other condition. It places your amount among published trials and quotes what they found; if you take an antidepressant or any medicine that acts on serotonin, are pregnant or breastfeeding, or have trouble sleeping that lasts, talk to your doctor or pharmacist. Some links on this site are affiliate links: I buy what I review at full price, and a commission never changes a verdict.