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Dietary supplement

L-Cysteine 500 mg Ingredients & Drug Interactions

by Puritan's Pride Premium

L-Cysteine 500 mg label
See full label image
Capsule Category: Amino Acid/protein
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking L-Cysteine 500 mg against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

L-Cysteine 500 mg is a dietary supplement by Puritan's Pride Premium with 1 active ingredient. Its ingredients are commonly taken for antioxidant support, skin and hair health, liver support.Based on those ingredients, 86 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are L-Cysteine. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against L-Cysteine 500 mg by Puritan's Pride Premium

Ask about any prescription or over-the-counter medication and we check it for interactions with L-Cysteine 500 mg by Puritan's Pride Premium — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
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HelloPharmacist Scorecard of L-Cysteine 500 mg by Puritan's Pride Premium

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

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Aug 13, 2026

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-cysteine, an amino acid (a building block your body uses to make proteins and other compounds). Each capsule delivers 500 mg.

The capsule itself also holds inactive ingredients — rice flour, gelatin, magnesium stearate, and silica — which are binders and fillers that help hold the supplement together.

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-cysteine product and its label doesn't state a use — see L-cysteine'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.

We don't have enough reliable evidence to rate L-cysteine for the conditions it's often promoted for — hair loss (androgenic alopecia), leg ulcers (venous leg ulcers), hangover, stroke, or gastritis. That doesn't mean it doesn't work; it means the studies aren't there yet to say either way.

If you're thinking about it for one of these uses, your doctor or pharmacist can help you weigh what evidence does exist.

The evidence, ingredient by ingredient L-cysteine

How safe is it?

Some data gaps
Safety Information · database check
Some gaps

Safety data exists for these ingredients, but with some important gaps.

Why this rating?
  • We hold adverse-effect (side-effect) data for 0 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-cysteine is generally well tolerated at the amounts found in food, but the safety of high-dose supplements like this one over long periods hasn't been studied well. Because long-term safety data is limited, use only if your doctor advises it.

The supplement is likely safe during pregnancy and breastfeeding, though you should talk with your doctor before taking any new supplement while pregnant or nursing.

Side effects, ingredient by ingredient L-cysteine

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — L-cysteine.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: diabetes medications.
  • For scale: 86 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.

If you take any antidiabetes drug (medication to lower blood sugar), check with your doctor or pharmacist before starting this product. L-cysteine may lower blood sugar on its own, which could increase the risk of going too low when combined with your medication.

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. Moderate medication interactions have been identified, and some safety-information gaps remain.

L-Cysteine 500 mg is a straightforward single-ingredient supplement that's generally well tolerated at food levels, but we don't have good evidence it works for the conditions it's marketed for. The main concern is if you take diabetes medications — you'll need to check with your doctor or pharmacist first because of the risk of low blood sugar.

If you have no diabetes medications and your doctor says it's okay, it's an option worth discussing.

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 May 24, 2023.

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-Cysteine 500 mg, straight from the product label.

Brand Puritan's Pride Premium
Barcode (UPC) 074312101007
Net contents 50 Rapid Release Capsule(s)
Market status On market
Date entered into DSLD May 24, 2023
DSLD ID 285038
Product type Amino Acid/protein
Supplement form Capsule
Dietary claims / uses Nutrient, All Other
Intended target group(s) Adult (18 - 50 Years), Gluten Free, Dairy Free, Sugar 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-Cysteine 500 mg by Puritan's Pride Premium, 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:
1 Capsule(s)
Maximum serving Sizes:
1 Capsule(s)
Servings per container
50
UPC/BARCODE
074312101007
IngredientAmount% DV
L-Cysteine500 mg--

Other ingredients: Rice Flour, Gelatin, Magnesium Stearate, Silica

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.
Formulation

Free form

Note: This product has an odor which is characteristic of l-cysteine.

No artificial color, flavor or sweetener, no preservatives, no sugar, no milk, no lactose, no soy, no gluten, no wheat, no yeast, no fish. Sodium free.

FDA Statement of Identity

Amino Acid Supplement

General Statements

Puritan’s Pride supplements are produced from the finest raw materials under our stringent quality control standards. Our state-of-the-art manufacturing and packaging facilities ensure you the highest quality nutritional supplements money can buy. When it comes to your health...choose the best.

To reorder item #100 www.puritan.com 1-800-645-1030 shop online www.puritan.com

Precautions

Warning: If you are pregnant, nursing, taking any medications or have any medical condition, consult your doctor before use.

Discontinue use and consult your doctor if any adverse reactions occur.

Keep out of reach of children.

Do not use if seal under cap is broken or missing.

Storage

Store at room temperature.

Brand IP Statement(s)

Copyright 2012 Puritan's Pride, Inc.

Seals/Symbols

QA Quality Assured

Suggested/Recommended/Usage/Directions

Directions: For adults, take one (1) capsule up to two times daily, preferably on an empty stomach.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

L-Cysteine 500 mg by Puritan's Pride Premium label

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

L-Cysteine 500 mg label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in L-Cysteine 500 mg by Puritan's Pride Premium

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

Serving size1 Capsule(s) Dosage formCapsule Servings per container50 Amounts shown are per serving.

L-Cysteine

Interacts with
86 drugs
500 mg per serving

L-cysteine is a sulfur-containing amino acid your body uses to make proteins and the antioxidant glutathione. Most people get enough from food, and su...

L-Cysteine monograph & interactions

Other (inactive) ingredients: Rice Flour, Gelatin, Magnesium Stearate, Silica. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Cysteine 500 mg by Puritan's Pride Premium Drug Interactions

Want to check YOUR meds against L-Cysteine 500 mg?

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
86Drugs
86 Moderate

Ingredients driving the most interactions

L-Cysteine 86

Individual Drug Interactions

The ingredients in L-Cysteine 500 mg interact with 86 drugs. Click any drug to see the details.

1 of the 1 ingredient in L-Cysteine 500 mg interact with drugs. Each result below shows which ingredient is responsible. L-Cysteine

Each ingredient & the kinds of drugs it affects

For each ingredient in L-Cysteine 500 mg 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-Cysteine1 drug type · 86 drugs

Antidiabetes Drugs

Theoretically, taking L-cysteine supplements with antidiabetes drugs might increase the risk of hypoglycemia.
Animal research suggests that L-cysteine can have hypoglycemic effects.

Likelihood Possible Evidence D
L-Cysteine full monograph & interactions
The maker

Brand information

Manufacturer and brand details for L-Cysteine 500 mg, from the product label.

Puritan's Pride Premium

See all Puritan's Pride Premium products
Name
Puritan's Pride, Inc.
City
Holbrook
State
NY
ZipCode
11741
Phone Number
1-800-645-1030
Web Address
www.puritan.com
Pharmacist Counseling Corner

L-Cysteine 500 mg by Puritan's Pride Premium: Common Questions

Does L-Cysteine 500 mg by Puritan's Pride Premium interact with any medications?
Yes. Based on its ingredients, L-Cysteine 500 mg has a known interaction with 86 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
L-Cysteine 500 mg 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.
Is L-cysteine safe during pregnancy or breastfeeding?
According to the data we hold, L-cysteine is likely safe during pregnancy and lactation. That said, it's always wise to talk with your doctor or pharmacist before taking any new supplement while pregnant or nursing, so they can review your full picture.
Does this supplement actually work for hair loss, ulcers, or hangovers?
We don't have enough reliable evidence to say whether L-cysteine works for those uses. The studies aren't there yet. Your doctor can help you decide if it's worth trying based on what smaller studies or clinical experience suggest.
What is L-cysteine, and what does it do in the body?
L-cysteine is an amino acid — one of the building blocks your body uses to make proteins and other important compounds. Your body makes some on its own, and you get some from food.
Is this supplement well tolerated?
L-cysteine at the amounts found in food is generally well tolerated. However, the safety of high-dose supplements like this 500 mg capsule over long periods hasn't been studied thoroughly, so caution is advised if you're taking it long-term.
Does this product contain any fillers or other inactive ingredients?
Yes — the capsule contains rice flour, gelatin, magnesium stearate, and silica as inactive ingredients. These are binders and fillers that help hold the supplement together.

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

Not sure if L-Cysteine 500 mg is safe with your meds?

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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-Cysteine 500 mg label
Go deeper

The Full Monographs Behind L-Cysteine 500 mg’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

L-cysteine

Interacts with 86 drugs

L-cysteine is a sulfur-containing amino acid your body uses to make proteins and the antioxidant glutathione. Most people get enough from food, and supplements are usually well tolerated, bu...

Read the full L-cysteine monograph →
Sources

Sources & How We Checked

L-Cysteine 500 mg'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 2 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-cysteine 2 references
  1. Dowlati Y, Maheux M, Meyer JH. The effect of oral L-cysteine on breast milk and plasma cysteine concentrations. Neuropsychiatr Dis Treat 2020;16:3163-3172.
  2. Lee S, Han KH, Nakamura Y, et al. Dietary L-cysteine improves the antioxidative potential and lipid metabolism in rats fed a normal diet. Biosci Biotechnol Biochem 2013;77(7):1430-4.

See these in context on the L-cysteine 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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