L-Cysteine Powder
by Source Naturals · powder · 3.53 ounces
- On the market (NIH)
- UPC 0 21078 00120 1
- DSLD label 274767
- Serving 1.2 g (1/4 Teaspoon)
- 83 servings
L-Cysteine Powder by Source Naturals lists one ingredient: 900 mg of L-cysteine per serving of 1.2 g. Its current label entered the NIH Dietary Supplement Label Database on November 22, 2022.
What is in L-Cysteine Powder?
Each row as the label prints it, per serving of 1.2 g. 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).
| Ingredient | Amount | % DV | Among products listing it |
|---|---|---|---|
| L-Cysteineas L-Cysteine Hydrochloride Monohydrate | 900 mg | Higher than 98% of 516 products listing cysteine (median 85 mg). |
Source: NIH ODS Dietary Supplement Label Database, label 274767 (entered November 22, 2022), version 9.4.0. See the label on DSLD or its label image (PDF). 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 900 mg of L-cysteine (filed by NIH under cysteine) is higher than 98% of the 516 cysteine products that print an amount; 7 list more.
The NIH database records one serving 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?
6 products list the very same ingredients; the nearest amounts come first.
- 100% Pure L-CysteineNutraBio same ingredients
- Cysteine 500 mgDr. Clark Research Association Dr. Clark Zentrum same ingredients
- L-Cysteine Free Form 500 mgVitamin World · off the market same ingredients
- L-Cysteine 500 mgDouglas Laboratories same ingredients
- L-Cysteine 500 mgVitamin World same ingredients
- L-Cysteine-SNutri-West same ingredients
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: 1/4 teaspoon per day between meals. If you experience stomach irritation, take with meals.
- Warnings
- Note: If you are pregnant, may become pregnant, or are breastfeeding, consult your health care professional before using this product.
- Do not use if either tamper-evident seal is broken or missing.
- Keep out of the reach of children.
- Allergens and what it does not contain
- Contains no yeast, dairy, egg, gluten, corn, soy or wheat. Contains no sugar, starch, salt, preservatives, or artificial color, flavor or fragrance.
- Storage
- Store in a cool, dry place.
Source: label statements in DSLD label 274767.
How many labels does L-Cysteine Powder have?
One label is on file, entered on November 22, 2022.
- Label 274767 (current) Entered November 22, 2022 · on the market · 3.53 ounces · UPC 0 21078 00120 1
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.