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Dietary supplement

L-Tryptophan Ingredients & Drug Interactions

by BulkSupplements.com

Powder Category: Amino Acid/protein
Most serious interaction: Major
The interaction bottom line Most serious interaction: Major

L-Tryptophan is a dietary supplement by BulkSupplements.com with 1 active ingredient. Its ingredients are commonly taken for sleep problems, low mood and depression, anxiety.Based on those ingredients, 394 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are L-Tryptophan. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

HelloPharmacist Scorecard of L-Tryptophan by BulkSupplements.com

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains one active ingredient: L-tryptophan, an amino acid your body uses to make serotonin and other important brain chemicals. The powder form delivers this ingredient without any other active components.

No inactive fillers or binders are included.

Does it work?

Couldn't assess
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not assessable

This is a single-ingredient L-tryptophan product and its label doesn't state a use — see L-tryptophan's own graded uses on its monograph.

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.

L-tryptophan's track record is mixed. For depression, the evidence leans toward it being ineffective.

For anxiety, bruxism (teeth grinding), premenstrual dysphoric disorder, and athletic performance, we don't have enough reliable evidence to rate whether it works. If you're considering it for any of these reasons, talk with your doctor about whether the current evidence supports it for your situation.

The evidence, ingredient by ingredient L-tryptophan

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

L-tryptophan is generally well tolerated when taken by mouth. Common side effects include belching, diarrhea, drowsiness, dry mouth, flatulence, headache, heartburn, lightheadedness, nausea, stomach pain, blurred vision, and vomiting.

There is one serious concern: a rare neurological disorder called eosinophilia-myalgia syndrome (EMS) was linked to L-tryptophan in the late 1980s, but nearly all cases traced back to contaminated product from a single Japanese manufacturer and happened before a 1990 FDA import limit took effect. During pregnancy, safety data is mixed—some evidence suggests it may be unsafe.

During breastfeeding, safety is not established, so it's best avoided. If you're pregnant or breastfeeding and interested in L-tryptophan, discuss it with your doctor or pharmacist for personalized advice.

Side effects, ingredient by ingredient L-tryptophan

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — L-tryptophan.
  • The most serious interaction on file is rated Major.
  • For scale: 394 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Check with your doctor or pharmacist before taking L-tryptophan if you use any central nervous system depressants (sleep aids, sedatives, pain relievers that cause drowsiness) or serotonergic drugs (many antidepressants, some migraine treatments, other psychiatric medications). The combination could intensify drowsiness or raise your serotonin level dangerously high.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no assessable stated purpose. Major medication interactions have been identified, and safety information is well characterized.

L-tryptophan may be worth considering if you're looking into amino acid supplements, but it comes with documented interactions with sleep aids, sedatives, and serotonin-related psychiatric drugs—and its effectiveness for common uses like depression or anxiety isn't well proved. If you take CNS depressants or any serotonergic medication, you'll need to check with your doctor or pharmacist before starting this product.

Pregnancy and breastfeeding require individual discussion with your healthcare provider.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Sep 24, 2021.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about L-Tryptophan, straight from the product label.

Brand BulkSupplements.com
Barcode (UPC) X000IVXQSP
Net contents 250 Gram(s); 8.8 Ounce(s)
Market status On market
Date entered into DSLD Sep 24, 2021
DSLD ID 254830
Product type Amino Acid/protein
Supplement form Powder
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Gluten Free, Dairy Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for L-Tryptophan by BulkSupplements.com, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
500 mg
Maximum serving Sizes:
500 mg
Servings per container
500
UPC/BARCODE
X000IVXQSP
IngredientAmount% DV
L-Tryptophan500 mg--

Other ingredients: None

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
General Statements

Clean & pure bulk supplements

FDA Disclaimer Statement

Warning: This product is not intended to diagnose, treat, cure, or prevent any disease.

Precautions

Always consult a physician before taking any dietary supplement.

Keep out of reach of children.

Formulation

Free of: Added sugar, soy, dairy, yeast, gluten, additives

Suggested/Recommended/Usage/Directions

Suggested use: As a dietary supplement, take 500 mg (about 1/5 tsp) once or twice daily, or as directed by a physician.

Storage

Store in a dry, cool place

See for yourself

L-Tryptophan by BulkSupplements.com label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

What’s inside

The Ingredients in L-Tryptophan by BulkSupplements.com

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size500 mg Dosage formPowder Servings per container500 Amounts shown are per serving.

L-Tryptophan

Interacts with
394 drugs
500 mg per serving

L-tryptophan is an essential amino acid the body uses to make serotonin and melatonin, and people take it to support sleep and mood. The evidence for...

L-Tryptophan monograph & interactions

Other (inactive) ingredients: None. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Tryptophan by BulkSupplements.com Drug Interactions

Want to check YOUR meds against L-Tryptophan?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

Go to the checker
394Drugs
248 Major 146 Moderate

Ingredients driving the most interactions

Each ingredient & the kinds of drugs it affects

For each ingredient in L-Tryptophan with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

L-Tryptophan2 drug types · 394 drugs

Cns Depressants

Theoretically, concomitant use of L-tryptophan with CNS depressants might cause additive sedative effects.
Clinical research shows that L-tryptophan can cause fatigue and drowsiness.

Likelihood Probable Evidence B
Serotonergic Drugs

Theoretically, combining L-tryptophan with serotonergic drugs might cause additive serotonergic effects.
L-tryptophan is a precursor to serotonin. Theoretically, combining serotonergic drugs with L-tryptophan might increase the risk of serotonergic side effects, including serotonin syndrome and cerebral vasoconstrictive disorders.

Likelihood Possible Evidence D
The maker

Brand information

Manufacturer and brand details for L-Tryptophan, from the product label.

BulkSupplements.com

See all BulkSupplements.com products
Name
BulkSupplements.com
Street Address
7511 Eastgate Rd
City
Henderson
State
NV
ZipCode
89011
Web Address
BulkSupplements.com
Pharmacist Counseling Corner

L-Tryptophan by BulkSupplements.com: Common Questions

Does L-Tryptophan by BulkSupplements.com interact with any medications?
Yes. Based on its ingredients, L-Tryptophan has a known interaction with 394 medications, including 248 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
L-Tryptophan contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
What is L-tryptophan supposed to do?
L-tryptophan is an amino acid your body uses to build serotonin, a brain chemical involved in mood and sleep. That's why it's often marketed for depression, anxiety, and sleep—though the evidence it actually works for these is limited or unclear.
Can I take this while pregnant?
Safety data for pregnancy is mixed. The data available advises some caution. Talk with your doctor before taking it during pregnancy; they can weigh the pros and cons for your specific situation.
Can I take this while breastfeeding?
Safety is not established for breastfeeding. It's best avoided unless your doctor advises otherwise. Check with your doctor or pharmacist about whether it's right for you.
What are the common side effects?
Most people tolerate it well, but common side effects include drowsiness, nausea, diarrhea, headache, flatulence, dry mouth, and lightheadedness. More serious effects are rare with modern products.
Does this work for depression?
The evidence suggests L-tryptophan is probably not effective for depression. If you're considering it for depression or anxiety, talk with your doctor about treatments with stronger evidence behind them.
Why was L-tryptophan banned in the U.S. before?
In 1989, a contaminated batch from one Japanese manufacturer caused over 1,500 cases of a rare neurological disorder called eosinophilia-myalgia syndrome. The FDA limited imports in 1990. Modern L-tryptophan is from different sources, but the history means you should buy from reputable manufacturers.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Not sure if L-Tryptophan is safe with your meds?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

L-Tryptophan label
Sources

Sources & How We Checked

L-Tryptophan's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 18 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

L-tryptophan 18 references
  1. Messiha FS. Fluoxetine: adverse effects and drug-drug interactions. J Toxicol Clin Toxicol 1993;31:603-30. PubMed
  2. Devoe LD, Castillo RA, Searle NS. Maternal dietary substrates and human fetal biophysical activity. The effects of tryptophan and glucose on fetal breathing movements. Am J Obstet Gynecol 1986;155:135-9. DOI
  3. Lieberman HR, Corkin S, Spring BJ. The effects of dietary neurotransmitter precursors on human behavior. Am J Clin Nutr 1985;42:366-70. PubMed
  4. U. S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Nutritional Products, Labeling, and Dietary Supplements. Information Paper on L-Tryptophan and 5-hydroxy-L-tryptophan, February 2001.
  5. Sullivan EA, Kamb ML, Jones JL, et al. The natural history of eosinophilia-myalgia syndrome in a tryptophan-exposed cohort in South Carolina. Arch Intern Med 1996;156:973-9. DOI
  6. Philen RM, Hill RH, Flanders WD, et al. Tryptophan contaminants associated with eosinophilia-myalgia syndrome. Am J Epidemiol 1993;138:154-9. PubMed
  7. Bohme A, Wolter M, Hoelzer D. L-tryptophan-related eosinophilia-myalgia syndrome possibly associated with a chronic B-lymphocytic leukemia. Ann Hematol 1998;77:235-8. PubMed
  8. Singhal AB, Caviness VS, Begleiter AF, et al. Cerebral vasoconstriction and stroke after use of serotonergic drugs. Neurology 2002;58:130-3. PubMed
  9. Priori R, Conti F, Luan FL, et al. Chronic fatigue: a peculiar evolution of eosinophilia myalgia syndrome following treatment with L-tryptophan in four Italian adolescents. Eur J Pediatr 1994;153:344-6..
  10. Klein R, Berg PA. A comparative study on antibodies to nucleoli and 5-hydroxytryptamine in patients with fibromyalgia syndrome and tryptophan-induced eosinophilia-myalgia syndrome. Clin Investig 1994;72:541-9.. PubMed
  11. Simat TJ, Kleeberg KK, Muller B, Sierts A. Synthesis, formation, and occurrence of contaminants in biotechnologically manufactured L-tryptophan. Adv Exp Med Biol 1999;467:469-80.. PubMed
  12. Shaw K, Turner J, Del Mar C. Tryptophan and 5-hydroxytryptophan for depression. Cochrane Database Syst Rev 2002;(1):CD003198. PubMed
  13. Kilbourne EM, Philen RM, Kamb ML, Falk H. Tryptophan produced by Showa Denko and epidemic eosinophilia-myalgia syndrome. J Rheumatol Suppl 1996;46:81-8.
  14. Horwitz RI, Daniels SR. Bias or biology: evaluating the epidemiologic studies of L-tryptophan and the eosinophilia-myalgia syndrome. J Rheumatol Suppl 1996;46:60-72.
  15. Shapiro S. Epidemiologic studies of the association of L-tryptophan with the eosinophilia-myalgia syndrome: a critique. J Rheumatol Suppl 1996;46:44-58.
  16. Mayeno AN, Gleich GJ. The eosinophilia-myalgia syndrome: lessons from Germany. Mayo Clin Proc 1994;69:702-4. PubMed
  17. Carr L, Ruther E, Berg PA, Lehnert H. Eosinophilia-myalgia syndrome in Germany: an epidemiologic review. Mayo Clin Proc 1994;69:620-5. PubMed
  18. Ullrich SS, Fitzgerald PCE, Giesbertz P, Steinert RE, Horowitz M, Feinle-Bisset C. Effects of intragastric administration of tryptophan on the blood glucose response to a nutrient drink and energy intake, in lean and obese men. Nutrients 2018;10(4). pii: PubMed

See these in context on the L-tryptophan monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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