L-Lysine 500 mg Ingredients & Drug Interactions
by NOW
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 NOW 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 NOW
Ask about any prescription or over-the-counter medication and we check it for interactions with L-Lysine 500 mg by NOW — 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 NOW
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 has one active ingredient: L-lysine hydrochloride, an amino acid your body needs for protein synthesis and immune function. The tablet also contains inactive ingredients — microcrystalline cellulose (a filler), vegetarian coating, silicon dioxide, and magnesium stearate — that help hold the tablet together and keep it shelf-stable.
Does it work?
Moderate evidence
L-lysine is possibly effective for herpes labialis (cold sores), meaning some evidence supports its use but more research would strengthen that claim. For child growth, pressure ulcers, and diabetic foot ulcers, the evidence isn't established in our data — we hold insufficient reliable evidence to rate how well it works for these uses.
How safe is it?
Well-documented data
L-lysine is generally well tolerated at typical doses, though high amounts may cause stomach upset, and long-term safety hasn't been well studied. The most common side effects reported orally are abdominal pain, diarrhea, and indigestion.
There is one case report of oral lysine linked to kidney inflammation that progressed to chronic kidney failure, though this is extremely rare. For pregnancy, supplement safety hasn't been well studied — lysine from food is fine, but talk with your doctor before taking a supplement.
For breastfeeding, there isn't enough reliable information, so caution is advised and you should discuss it with your doctor or pharmacist.
Meds to double-check
Minor interactions only
If you take a 5-HT4 agonist (a medication for certain gut conditions), check with your pharmacist before starting — lysine may reduce how well it works. For all other medications, no interactions are documented in our data for the ingredients we could check.
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 is a reasonable choice if you're looking to manage cold sores, since it's possibly effective for that. If you take a 5-HT4 agonist, check with your pharmacist before adding this — it may weaken that medication's effect.
Pregnant or breastfeeding? Talk to your doctor first.
Otherwise, it's generally well tolerated, but let your pharmacist know if you develop stomach upset or diarrhea.
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 Aug 22, 2024.
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 | NOW |
|---|---|
| Barcode (UPC) | 733739001023 |
| Net contents | 250 Tablet(s) |
| Market status | On market |
| Date entered into DSLD | Aug 22, 2024 |
| DSLD ID | 315752 |
| Product type | Amino Acid/protein |
| Supplement form | Tablet Or Pill |
| Dietary claims / uses | Nutrient, All Other, Structure/Function |
| Intended target group(s) | Vegan, Vegetarian, Adult (18 - 50 Years), Kosher, Gluten Free, Dairy 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 NOW, sourced from the NIH Dietary Supplement Label Database.
Supplement Facts
| Ingredient | Amount | % DV |
|---|---|---|
| L-Lysine Hydrochloride | 637 mg | -- |
| L-Lysine | 500 mg | -- |
Other ingredients: Microcrystalline Cellulose, Vegetarian Coating, Silicon Dioxide, Magnesium Stearate
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.
Suggested/Recommended/Usage/Directions
Suggested Usage: Take 1 tablet 1 to 3 times daily.
Formula
Lysine is an essential amino acid that must be obtained through the diet or through supplementation. Lysine is necessary for the production of all proteins in the body, and is required for the maintenance of the structural proteins collagen and elastin, which form all connective tissue such as skin, tendon, and bone. Lysine is also a precursor to carnitine, which is needed for fat metabolism and energy production. In addition, Lysine may help to support a healthy immune system and proper cardiovascular function.
Triangle K (Kosher)
NOW L-Lysine is a Pharmaceutical Grade essential amino acid.
Essential Amino Acid
FDA Disclaimer Statement
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.
Precautions
Caution: For adults only. Keep out of reach of children.
Consult physician if pregnant/nursing, taking medication, or have a medical condition.
Not manufactured with wheat, gluten, soy, milk, egg, fish, shellfish, tree nut or sesame ingredients. Produced in a GMP facility that processes other ingredients containing these allergens.
Storage
Store in a cool, dry place after opening.
Formulation
Supports Collagen Synthesis Healthy Immune Function
Non-GMO
Vegetarian/Vegan
Made and quality tested in the USA with globally sourced ingredients.
Not manufactured with wheat, gluten, soy, milk, egg, fish, shellfish, tree nut or sesame ingredients.
Natural color variation may occur in this product.
Seals/Symbols
Triangle K (Kosher)
GMP Quality Assured
FDA Statement of Identity
A Dietary Supplement
General Statements
Amino Acids Family owned since 1968.
Is this label outdated? Report a formula or label change and our pharmacy team will review it.
L-Lysine 500 mg by NOW 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 NOW
This is the 1 active ingredient this product is made of. Select it to open its full monograph.
Serving size1 Tablet(s) Dosage formTablet Or Pill Servings per container250 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: Microcrystalline Cellulose, Vegetarian Coating, Silicon Dioxide, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.
L-Lysine 500 mg by NOW Drug Interactions
HelloPharmacist Interaction Report
NOW L-Lysine 500 mg contains one active ingredient, L-lysine hydrochloride, which has one documented drug interaction.
L-lysine may reduce the effects of 5-HT4 agonists (a type of medication used for certain gastrointestinal conditions). Animal research suggests lysine acts as a partial blocker of serotonin receptor 4, which is how these drugs work — so taking them together could weaken the medication's effect.
This is rated a Minor interaction.
Read the full breakdown — every affected drug type, severity by severity
Additionally, no other medication interactions are documented in our data for L-lysine. That doesn't mean none exist — it means we haven't found documented interactions with other drug types.
If you take a 5-HT4 agonist or any other prescription medication, run them through the interaction checker below before you start this supplement.
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.
NOW
See all NOW products- Name
- NOW Foods
- Street Address
- 395 S. Glen Ellyn Rd.
- City
- Bloomingdale
- State
- IL
- ZipCode
- 60108
- Web Address
- nowfoods.com
L-Lysine 500 mg by NOW: Common Questions
Does L-Lysine 500 mg by NOW interact with any medications?
How can one product interact with so many drugs?
Where does this information come from?
Can I take L-lysine if I'm pregnant or breastfeeding?
What are the most common side effects?
Does L-lysine really work for cold sores?
Will this help with pressure ulcers or diabetic foot ulcers?
What's in this tablet besides the lysine?
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