L-Lysine 500 mg Ingredients & Drug Interactions
What is this page for?
First and foremost: checking L-Lysine 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
L-Lysine 500 mg is a dietary supplement by Natural Factors with 1 active ingredient. Its ingredients are commonly taken for cold sores (herpes labialis), genital herpes outbreaks, supporting protein and collagen formation.Based on those ingredients, 1 medication has a known interaction with it, the most serious rated minor. The ingredients most likely to interact are L-Lysine. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.
Check Your Meds Against L-Lysine 500 mg by Natural Factors
Ask about any prescription or over-the-counter medication and we check it for interactions with L-Lysine 500 mg by Natural Factors — and tell you which ingredient is responsible.
AI summaries are generated from our interaction database for education only — always confirm with your pharmacist. How we use AI
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HelloPharmacist Scorecard of L-Lysine 500 mg by Natural Factors
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.
What’s inside
Full disclosure
This product contains one active ingredient: L-lysine, an amino acid your body uses to support immune function and tissue repair. At 500 mg per capsule, you're getting a straightforward single-ingredient supplement with no other actives.
The capsule itself is made from vegetarian material, and the other ingredients — rice powder, magnesium stearate, and silica — are inactive fillers and processing aids.
Does it work?
Moderate evidence
L-lysine is possibly effective for cold sores (herpes labialis). The evidence suggests it may help, though it's not definitive.
For other uses listed — child growth, pressure ulcers, and diabetic foot ulcers — there isn't enough reliable evidence to know whether it works. If you're considering lysine for cold sores, it's worth a try, but talk it over with your doctor if you're thinking about it for any other purpose.
How safe is it?
Well-documented data
Lysine is generally well tolerated at normal doses. The most common side effects from oral use are stomach upset — including abdominal pain, diarrhea, and indigestion — and these tend to be mild.
High amounts may cause more stomach trouble, and the long-term safety of high-dose supplements hasn't been thoroughly studied. There's one rare case report of kidney problems linked to lysine, though this is not common.
For pregnancy, the safety data on lysine supplements isn't well studied, so talk with your doctor before taking it. Breastfeeding safety isn't well established either — check with your doctor or pharmacist for personalized advice.
Getting lysine from food is fine during both.
Meds to double-check
Minor interactions only
If you take a 5-HT4 agonist (a medication that works on serotonin receptor 4 to help with digestive motility), check with your doctor or pharmacist before adding this lysine supplement — it may reduce the drug's effectiveness. No other medication interactions are documented in our data for lysine, but run your full medication list through the search tool on this page to be sure.
The bottom line
Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Only minor medication interactions are documented, and safety information is well characterized.
L-lysine may help with cold sores if you want to try it, but the evidence isn't rock-solid. If you take a 5-HT4 agonist (a digestive medication), check with your doctor or pharmacist first — this supplement could reduce how well it works.
Stomach upset is possible, especially at higher doses. Talk with your doctor or pharmacist before starting, especially if you're pregnant, breastfeeding, or taking any medications.
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 22, 2020.
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
General information
Key facts about L-Lysine 500 mg, straight from the product label.
| Brand | Natural Factors |
|---|---|
| Barcode (UPC) | 068958028231 |
| Net contents | 90 Vegetarian Capsule(s) |
| Market status | On market |
| Date entered into DSLD | May 22, 2020 |
| DSLD ID | 220448 |
| Product type | Amino Acid/protein |
| Supplement form | Capsule |
| Dietary claims / uses | Nutrient, All Other, Structure/Function |
| Intended target group(s) | Vegan, Vegetarian, Adult (18 - 50 Years), Gluten Free, Dairy Free, Sugar Free |
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-Lysine 500 mg by Natural Factors, sourced from the NIH Dietary Supplement Label Database.
Supplement Facts
| Ingredient | Amount | % DV |
|---|---|---|
| L-Lysine | 1000 mg | -- |
Other ingredients: Vegetarian Capsule, Rice powder, Magnesium Stearate, Silica
Tap any ingredient to jump to its full detail below.
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.
Seals/Symbols
isura Non-GMO - Mass Spec Documentation Lab tested
Purity & Potency Guaranteed
Suggested/Recommended/Usage/Directions
Suggested Usage: 2 capsules 3 times per day with meals or as directed by a health professional.
Precautions
Cautions: As with any supplement, consult your health professional before use if you are pregnant, breastfeeding, or trying to conceive, or if you are taking medication, have a medical condition, or anticipate surgery.
Keep out of the reach of children.
Sealed for your protection. Do not use if seal is broken.
Formula
L-Lysine is an essential amino acid necessary for growth, development tissue maintenance, and repair.
Formulation
L-Lysine supports a healthy immune system and is one of the nine essential amino acids that the body needs to manufacture proteins. Natural Factors amino acids are the highest quality pharmaceutical grade products available. Manufactured by Natural Factors to ensure safety and potency in accordance with Good Manufacturing Practices (GMP) of the FDA and Health Canada.
Contains no artificial colors, preservatives, or sweeteners; no dairy, sugar, wheat, gluten, yeast, soy, corn, egg, fish, shellfish, animal products, salt, tree nuts, or GMOs.
Suitable for vegetarians/vegans.
Free form amino acid Healthy immune system
Storage
For freshness, store in a cool, dry place.
FDA Disclaimer Statement
This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
General Statements
Product of Canada. Recyclable container and label.
FDA Statement of Identity
Dietary Supplement
Is this label outdated? Report a formula or label change and our pharmacy team will review it.
L-Lysine 500 mg by Natural Factors label
The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.
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)The Ingredients in L-Lysine 500 mg by Natural Factors
This is the 1 active ingredient this product is made of. Select it to open its full monograph.
Serving size2 Vegetarian Capsule(s) Dosage formCapsule Servings per container45 Amounts shown are per serving.
L-Lysine
Interacts with1 drug
Lysine is an essential amino acid your body cannot make on its own, so it must come from food or supplements. People most often take extra lysine to t...
L-Lysine monograph & interactionsOther (inactive) ingredients: Vegetarian Capsule, Rice powder, Magnesium Stearate, Silica. These complete the product’s ingredient list but are not active constituents.
L-Lysine 500 mg by Natural Factors Drug Interactions
HelloPharmacist Interaction Report
L-Lysine 500 mg by Natural Factors interacts with one medication type.
Through its lysine content, this product may reduce the effects of 5-HT4 agonists — a class of drugs used to treat certain digestive and motility issues. Animal research suggests lysine blocks serotonin receptor 4, which is the same target these medications work on, so taking them together could theoretically weaken the drug's effect.
Read the full breakdown — every affected drug type, severity by severity
Although this interaction is rated Minor, if you take a 5-HT4 agonist, check with your doctor or pharmacist before starting lysine to confirm whether this product is right for you. Altogether, these interactions span 1 individual medication.
You can search for your exact medications using the tool on this page to see if any are affected.
Check your own medications below · Editorial policy · How we use AI
Want to check YOUR meds against L-Lysine 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 checkerIngredients driving the most interactions
Individual Drug Interactions
The ingredients in L-Lysine 500 mg interact with 1 drug. Click any drug to see the details.
1 of the 1 ingredient in L-Lysine 500 mg interact with drugs. Each result below shows which ingredient is responsible. L-Lysine
TegaserodZelnorm
How Tegaserod interacts with L-Lysine 500 mg — through 1 ingredient. Tap an ingredient for the detail:
L-lysine5-ht4 Agonists Minor
Interaction Summary
Theoretically, lysine may reduce the effects of 5-HT4 agonists.
Read the full L-lysine + Tegaserod interactionEach ingredient & the kinds of drugs it affects
For each ingredient in L-Lysine 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-Lysine
5-Ht4 Agonists
Theoretically, lysine may reduce the effects of 5-HT4 agonists.
Animal research suggests that L-lysine is a partial serotonin receptor 4 (5-HT4) antagonist and inhibits diarrhea induced by the 5-HT4 agonist, 5-hydroxytryptophane.
Brand information
Manufacturer and brand details for L-Lysine 500 mg, from the product label.
L-Lysine 500 mg by Natural Factors: Common Questions
Does L-Lysine 500 mg by Natural Factors interact with any medications?
How can one product interact with so many drugs?
Where does this information come from?
Will this help my cold sores?
Is it safe to take long-term?
Can I take this while pregnant?
What's the difference between lysine from food and this supplement?
Can high doses cause problems?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Not sure if L-Lysine 500 mg is safe with your meds?
Our pharmacists answer your medication & supplement questions — free.
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.
The Full Monographs Behind L-Lysine 500 mg’s Ingredients
Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.
Sources & How We Checked
L-Lysine 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.
- NIH Dietary Supplement Label Database (DSLD) — The official product label on file for this supplement.
- Natural Medicines (Therapeutic Research Center) — Evidence-graded clinical reference behind the ingredient interaction data.
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 7 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.
Lysine 7 references
- Thein DJ, Hurt WC. Lysine as a prophylactic agent in the treatment of recurrent herpes simplex labialis. Oral Surg Oral Med Oral Pathol 1984;58:659-66. PubMed
- McCune MA, Perry HO, Muller SA, O'Fallon WM. Treatment of recurrent herpes simplex infections with L-lysine monohydrochloride. Cutis 1984;34:366-73.
- DiGiovanna JJ, Blank H. Failure of lysine in frequently recurrent herpes simplex infection. Treatment and prophylaxis. Arch Dermatol 1984;120:48-51. DOI
- Milman N, Scheibel J, Jessen O. Lysine prophylaxis in recurrent herpes simplex labialis: a double-blind, controlled crossover study. Acta Derm Venereol 1980;60:85-7.
- Griffith RS, Walsh DE, Myrmel KH, et al. Success of L-lysine therapy in frequently recurrent herpes simplex infection. Treatment and prophylaxis. Dermatologica 1987;175:183-90. DOI
- Lo JC, Chertow GM, Rennke H, Seifter JL. Fanconi's syndrome and tubulointerstitial nephritis in association with L-lysine ingestion. Am J Kidney Dis 1996;28:614-7. PubMed
- Smriga M, Torii K. L-Lysine acts like a partial serotonin receptor 4 antagonist and inhibits serotonin-mediated intestinal pathologies and anxiety in rats. Proc Natl Acad Sci U S A. 2003 Dec 23;100(26):15370-5.
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