PlainVitamins

L-Tryptophan

by Source Naturals · capsule · 30 capsules

  • On the market (NIH)
  • UPC 0 21078 01983 1
  • DSLD label 73847
  • Serving 1 to 3 capsules; amounts per 3 capsules
  • 10 servings

L-Tryptophan by Source Naturals lists 2 ingredients, 2 with an amount per serving of 3 capsules, such as 575 mcg of iron and 1.5 g of L-tryptophan. Its current label entered the NIH Dietary Supplement Label Database on May 24, 2017.

What is in L-Tryptophan?

Each row as the label prints it, per serving of 3 capsules. The capsule beside an amount places it among every product in the NIH database that lists the same ingredient: the bar is the middle half of their amounts, the line in it the median, the whiskers the 10th and 90th percentiles; the green tick is the FDA Daily Value and the red dashed tick the adult upper limit (IOM).

L-Tryptophan: Supplement Facts rows against the market (DSLD label 73847, January 2026 release)
IngredientAmount% DVAmong products listing it
IronIron Note: naturally occurring575 mcg3%Iron in L-Tryptophan against 6,910 products0.575 mg per serving; the middle half of products list 1.2 mg to 18 mg, the median 5 mg.DV 18 mgUL 45 mg0.575 mg

89% of 6,910 products listing iron give more (median 5 mg). Per day at the most servings: 1.73 mg.

L-Tryptophan1.5 gTryptophan in L-Tryptophan against 605 products1,500 mg per serving; the middle half of products list 55 mg to 471 mg, the median 123 mg.1,500 mg

Higher than 98% of 605 products listing tryptophan (median 123 mg). Per day at the most servings: 4,500 mg.

Source: NIH ODS Dietary Supplement Label Database, label 73847 (entered May 24, 2017), version 9.4.0. See the label on DSLD. Amounts are what the maker printed; DSLD does not test products. Daily Values: the FDA's Daily Value page.

Is that a lot?

The rows in the top or bottom tenth of the products that list the same ingredient, and any above the adult upper limit at the most servings a day the directions give:

  • Its 1,500 mg of L-tryptophan (filed by NIH under tryptophan) is higher than 98% of the 605 tryptophan products that print an amount; 8 list more.

The NIH database records 1 to 3 servings a day from the label's directions; its % Daily Values are for adults and children 4 or more years of age. The directions as printed are further down this page.

The Tolerable Upper Intake Level is the most of a nutrient per day, from food, water and supplements together, that is likely to pose no risk for almost all adults (Institute of Medicine, 2011). It does not apply under medical supervision. This page compares labels; it is not medical advice.

Sources: amounts from the DSLD label; Daily Values from 21 CFR 101.9(c)(8)(iv); adult upper limits from the Institute of Medicine's DRI summary tables (2011). How positions are computed.

Which products have the closest formulas?

2 products list the very same ingredients; the nearest amounts come first.

Source: ingredient lists of every product's current label in DSLD (version 9.4.0); similarity weights each shared ingredient by how rare it is.

What does the label say about taking it?

Quoted from the label as DSLD transcribed it: the maker's words, including any claim about what the product does, which the FDA has not evaluated and PlainVitamins does not endorse.

Directions
Suggested Use: 1 capsule three times daily, between meals and preferably with fruit juice. To support restful sleep, take 3 capsules before bed.
Warnings
Do not use if either tamper-evident seal is broken or missing.
Keep out of the reach of children.
Caution: If you are pregnant, may become pregnant, breastfeeding, or are taking medications such as SSRIs or MAOIs consult your health care professional before using this product.
Storage
Store in a cool, dry place.

Source: label statements in DSLD label 73847.

What else is on the label?

Other ingredients: Gelatin, Silica, Magnesium Stearate, Dibasic Calcium Phosphate, Microcrystalline Cellulose.

How many labels does L-Tryptophan have?

2 labels are on file under this name since May 24, 2017: other sizes, label designs and reformulations. The current one leads this page.

  1. Label 73851 Entered May 24, 2017 · off the market December 22, 2021 · 120 tablets · UPC 0 21078 01980 0
  2. Label 73847 (current) Entered May 24, 2017 · on the market · 30 capsules · UPC 0 21078 01983 1

DSLD also links this label to: L-Tryptophan 500 mg (package size difference, same product), L-Tryptophan 500 mg (package size difference, same product), L-Tryptophan 500 mg (package size difference, same product), L-Tryptophan 500 mg (package size difference, same product).

Source: DSLD label entry and market events, version 9.4.0 (labels entered through September 25, 2025).

Who makes it?

The label names Source Naturals, Inc. (distributor), Santa Cruz, CA. All Source Naturals products.

Where next?