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Ingredient guide

How much L-tryptophan per day?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Adults need about 4 to 5 mg of tryptophan per kg of body weight a day, roughly 280 to 350 mg at 70 kg, and food usually supplies about 826 mg. Supplement studies used 0.14 to 5 g a day, and the effect on night waking was clearest at 1 g or more.1,2,3,4,5

Key facts

  • Adults over 60 needed about 3.9 mg per kg a day in a 2026 study.6
  • Healthy young women took up to 5 g a day for 21 days without adverse effects on the measures checked.4
  • Some adults take 4 to 5 g a day on their own, about 60 to 70 mg per kg.2
  • Side effects were reported mainly at 70 to 200 mg per kg.2

What your body needs

Adults need about 4 to 5 mg of tryptophan per kg of body weight a day: 4 mg is the average requirement, and a 2012 review gives 5 mg. For a 70 kg adult, that is about 280 to 350 mg.1,2

Daily need at 4 to 5 mg per kg of body weight1,2
Body weightDaily need
50 kg200 to 250 mg
70 kg280 to 350 mg
90 kg360 to 450 mg
110 kg440 to 550 mg

A 2026 study put the need of adults aged 60 to 79 at about 3.9 mg per kg a day, with no difference between men and women.6

The 4 mg figure itself rests on a study in young women, which is one reason a team measured older adults directly in 2026. Their result came out close to it.6

What food already gives you

US adults eat about 826 mg of tryptophan a day, around three times the average need, and fewer than 1 percent fall below the requirement for any essential amino acid. For most people, then, a supplement is not needed to reach the requirement.1,7

Amounts used in supplement studies

Supplement studies have used 0.14 g to 5 g a day. The effect on night waking was clearest at 1 g or more, and healthy young women took up to 5 g a day for three weeks without adverse effects on the measures checked.3,4,5

May reduce time spent awake during the night, at 1 g or more a day*5,8

Early evidence

A 2022 meta-analysis pooled four trials and found that tryptophan shortened the time people spent awake after first falling asleep, with a larger effect at 1 g a day or more than at lower amounts. It did not change the other parts of sleep that were measured. NIH's center for complementary health says it is unclear how tryptophan works and describes the data as very limited.

Amount studied: 1 g or more a day; smaller amounts had less effect

The mood trials covered 0.14 to 3 g a day, taken on top of normal meals. In the three-week dose trial in young women, none of the amounts from 1 to 5 g a day changed mood scores.3,4

How our Sleep formula compares

What’s in ours

  • Sleep: L-Tryptophan, 100 mg per serving, from the label

At 100 mg per serving, the formula sits well below the 1 g level where the night waking effect was clearest, and adds about an eighth to what a typical diet already supplies. The studies tested tryptophan alone, not alongside melatonin and herbs.1,5

Upper amounts, and who should not take it

We found no official upper limit for tryptophan supplements, and researchers say a thorough dose-by-dose safety assessment has not been done. In one trial, 17 healthy young women took up to 5 g a day for 21 days with no adverse effects on the measures checked.2,4

The amounts some people choose for themselves, 4 to 5 g a day or about 60 to 70 mg per kg, come close to the 70 to 200 mg per kg at which side effects such as tremor, nausea and dizziness were reported.2

  • Do not take it if you take an MAOI antidepressant such as phenelzine.9
  • Ask first if you take any antidepressant or other medicine that raises serotonin. The labels give no amount of tryptophan that avoids the risk.8,10

Questions people ask

How many mg of L-tryptophan should I take for sleep?

The pooled sleep trials found the clearest effect at 1 g or more a day, and the evidence is early. That is what was studied, not a recommendation. Ask your doctor first, especially if you take any medicine.5

Is 500 mg of tryptophan a day too much?

It is above the daily need of most adults but below the roughly 826 mg the average US adult eats from food, and far below the 5 g a day tested for three weeks in young women. With an antidepressant or another serotonin medicine, though, ask first whatever the amount.1,4

Does body weight change how much you need?

Yes. At 4 to 5 mg per kg, a 50 kg adult needs about 200 to 250 mg a day and a 90 kg adult about 360 to 450 mg. The supplement studies we read reported fixed daily amounts rather than amounts by weight.1,2,3

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Sources

  1. Lieberman HR, Agarwal S, Fulgoni VL 3rd. Tryptophan Intake in the US Adult Population Is Not Related to Liver or Kidney Function but Is Associated with Depression and Sleep Outcomes. J Nutr. 2016;146(12):2609S-2615S. Opened 2026-10-07.
  2. Fernstrom JD. Effects and side effects associated with the non-nutritional use of tryptophan by humans. J Nutr. 2012;142(12):2236S-2244S. Opened 2026-10-07.
  3. Kikuchi AM, Tanabe A, Iwahori Y. A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioning. J Diet Suppl. 2021;18(3):316-333. Opened 2026-10-07.
  4. Hiratsuka C, Fukuwatari T, Sano M, Saito K, Sasaki S, Shibata K. Supplementing healthy women with up to 5.0 g/d of L-tryptophan has no adverse effects. J Nutr. 2013;143(6):859-866. Opened 2026-10-07.
  5. Sutanto CN, Loh WW, Kim JE. The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression. Nutr Rev. 2022;80(2):306-316. Opened 2026-10-07.
  6. Wang Z, Tomlinson C, Pencharz P, Li B, Kong D, Elango R, Courtney-Martin G. Dietary Tryptophan Requirements in Adults Aged >60 Years Is Not Affected by Sex or Decades of Age. J Nutr. 2026;156(11):101827. Online ahead of print. Opened 2026-10-07.
  7. Berryman CE, Cheung SN, Collette EM, Pasiakos SM, Lieberman HR, Fulgoni VL 3rd. Amino Acid Intake and Conformance With the Dietary Reference Intakes in the United States: Analysis of the National Health and Nutrition Examination Survey, 2001-2018. J Nutr. 2023;153(3):749-759. Opened 2026-10-07.
  8. National Center for Complementary and Integrative Health. Sleep Disorders and Complementary Health Approaches. Bethesda (MD): National Institutes of Health. Last updated May 2024. Opened 2026-10-07.
  9. Phenelzine sulfate tablets: prescribing information (Mylan Pharmaceuticals Inc.). DailyMed, U.S. National Library of Medicine. Published May 25, 2026. Opened 2026-10-07.
  10. Sertraline hydrochloride tablets: prescribing information (Cipla USA Inc.). DailyMed, U.S. National Library of Medicine. Published June 23, 2026. Opened 2026-10-07.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.