Medically Reviewed on 1/5/2023

Generic Name: l-tryptophan

Other Names: tryptophan

Drug Class: Herbals

What is l-tryptophan, and what is it used for?

L-tryptophan is an essential amino acid required for the synthesis of proteins, enzymes, muscles, and chemicals (neurotransmitters) such as serotonin and melatonin that nerve cells use for signaling.

L-tryptophan supplements are used as an adjunct to antidepressant therapy to treat depressive disorders. L-tryptophan supplements are also used for many other conditions including anxiety, insomnia, teeth grinding (bruxism), premenstrual syndrome symptoms, and migraine headaches.

L-tryptophan is not naturally synthesized in the body and must be obtained from dietary intake. Some good sources of l-tryptophan include milk, cheese, turkey, chicken, egg whites, fish, oats, peanuts, and sesame, sunflower, and pumpkin seeds. In general, the body's needs for l-tryptophan can be met with a healthy, balanced diet.

Is l-tryptophan good for depression?

Supplemental l-tryptophan can increase the availability of l-tryptophan for the synthesis of the neurotransmitters, serotonin, and melatonin. Serotonin’s functions include the regulation of mood, sleep, appetite and digestion, while melatonin promotes nighttime sleep. Low levels of serotonin may be implicated in depression and mood disorders. L-tryptophan is likely effective for depression, however, there are insufficient scientific studies to support most of its other uses.


  • Do not take l-tryptophan if you are hypersensitive to any of the components in the formulation.
  • L-tryptophan has been associated with hypersensitivity reactions including rash, itching, hives, swelling, muscle pain and wheezing. Use with caution.
  • Higher l-tryptophan levels may increase the risk for cataract formation, especially if exposed to ultraviolet (UV) light.
  • Serotonin syndrome, a potentially life-threatening drug reaction, can occur if l-tryptophan is taken simultaneously with other drugs that increase serotonin levels, including selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs).
  • Use l-tryptophan with caution in patients with diabetes mellitus.
  • Use with caution in patients with bladder cancer.
  • L-tryptophan may increase the risk of lung conditions such as emphysema and pulmonary edema in patients with absence of hydrochloric acid in the stomach (achlorhydria).
  • L-tryptophan can cause amino acid imbalance in patients who are protein-deprived.
  • Some bipolar patients are acutely sensitive and would not tolerate dosages higher than 1-2 g/day.
  • In patients with depression, clinical worsening and suicide ideation may occur despite taking medication.


Learn to Spot Depression: Symptoms, Warning Signs, Medication See Slideshow

What are the side effects of l-tryptophan?

Common side effects of l-tryptophan include:

Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

What are the dosages of l-tryptophan?



  • 8-12 g/d orally divided four or three times daily
  • Lower dosage effective in combination with other antidepressants


  • Take with low-protein, carbohydrate-rich meals or snacks


  • Safety and efficacy not established


  • L-tryptophan overdose can cause agitation, confusion, diarrhea, fever, overactive reflexes, poor coordination, restlessness, shivering, sweating, uncontrolled excitement, trembling or shaking, twitching, and vomiting.
  • Overdose may be treated with discontinuation of l-tryptophan and symptomatic and supportive care.

What drugs interact with l-tryptophan?

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

  • L-tryptophan has no known severe interactions with other drugs.
  • Serious interactions of L-tryptophan include:
  • L-tryptophan has moderate interactions with at least 54 different drugs.
  • L-tryptophan has no known mild interactions with other drugs.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider about all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or healthcare provider if you have any questions about the medication.

Pregnancy and breastfeeding

  • L-tryptophan absorbed from food is likely safe during pregnancy. Avoid taking L-tryptophan supplements if you are pregnant.
  • There isn’t reliable information on the use of l-tryptophan in nursing mothers. Avoid use if you are breastfeeding.

What else should I know about l-tryptophan?

  • L-tryptophan supplements are possibly safe for most adults when taken orally in recommended doses for up to 3 weeks.
  • Check with your healthcare provider before taking any dietary supplement, including l-tryptophan.
  • Take l-tryptophan exactly as prescribed or as per label instructions.
  • Dietary supplements often contain many ingredients. Check labels for the components in the l-tryptophan product you choose.
  • L-tryptophan is marketed as a dietary supplement and is not regulated by the FDA. Products may differ in formulations and strengths, and labels may not always match contents; exercise caution in choosing your product.
  • L-tryptophan may impair physical and mental abilities. Avoid performing tasks that require mental alertness, such as driving and operating heavy machinery while taking the supplement.
  • Store safely out of reach of children.
  • In case of overdose, seek medical help or contact Poison Control.

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L-tryptophan supplements are used as an adjunct to antidepressant therapy to treat depressive disorders. L-tryptophan supplements are also used for many other conditions including anxiety, insomnia, teeth grinding (bruxism), premenstrual syndrome symptoms, and migraine headaches. Common side effects of l-tryptophan include nausea, dry mouth (xerostomia), loss of appetite (anorexia), vomiting, stomach pain, diarrhea, rash, hives (urticaria), itching (pruritus), swelling (edema), muscle pain (myalgia), wheezing, dizziness, drowsiness, headache, blurry vision, serotonin syndrome, and sexual disinhibition. Do not take if pregnant or breastfeeding.

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You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Medically Reviewed on 1/5/2023