L-Lysine Ingredients & Drug Interactions
by NOW
What is this page for?
First and foremost: checking L-Lysine 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 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 by NOW
Ask about any prescription or over-the-counter medication and we check it for interactions with L-Lysine 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 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
L-Lysine by NOW contains one active ingredient: L-Lysine Hydrochloride, an amino acid (a building block of protein). This product has no other inactive ingredients listed.
Does it work?
Couldn't assess
L-Lysine is possibly effective for herpes labialis, also known as cold sores. The evidence for child growth, pressure ulcers, and diabetic foot ulcers is insufficient — the data we hold doesn't establish whether it works for these uses.
How safe is it?
Well-documented data
L-Lysine is generally well tolerated at typical doses. High amounts may cause stomach upset, and long-term safety from supplements hasn't been well studied.
The most common side effects reported are abdominal pain, diarrhea, and indigestion. One case report linked oral lysine to kidney inflammation progressing to chronic kidney failure, though this is rare.
Lysine from food is fine in pregnancy, but supplement safety during pregnancy is not well studied — check with your doctor first. There isn't enough reliable information on supplement use while breastfeeding, so caution is advised.
Meds to double-check
Minor interactions only
The one medication type to double-check before taking this product is 5-HT4 agonists. Lysine may theoretically reduce their effects.
Run your exact medications through the search tool on this page.
The bottom line
Scorecard at a glanceFully disclosed formula with no assessable stated purpose. Only minor medication interactions are documented, and safety information is well characterized.
L-Lysine is a single-amino-acid supplement possibly effective for cold sores. If you take 5-HT4 agonist drugs, check with us before starting.
Pregnant or breastfeeding? Talk to your doctor or pharmacist first — the safety data is still limited.
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 Jul 25, 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, straight from the product label.
| Brand | NOW |
|---|---|
| Barcode (UPC) | 733739002402 |
| Net contents | 1 lb; 454 Gram(s) |
| Market status | On market |
| Date entered into DSLD | Jul 25, 2024 |
| DSLD ID | 314444 |
| Product type | Amino Acid/protein |
| Supplement form | Powder |
| 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 by NOW, sourced from the NIH Dietary Supplement Label Database.
Supplement Facts
| Ingredient | Amount | % DV |
|---|---|---|
| L-Lysine Hydrochloride | 552 mg | -- |
| L-Lysine | 435 mg | -- |
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 1/4 level teaspoon 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.
Consult physician if pregnant/nursing, taking medication, or have a medical condition.
Keep out of reach of children.
Do not eat freshness packet enclosed.
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.
Formulation
Natural color variation may occur in this product.
Pure Powder Supports collagen synthesis Healthy immune function
Non-GMO
Vegetarian/Vegan
Not manufactured with wheat, gluten, soy, milk, egg, fish, shellfish, tree nut or sesame ingredients.
Storage
Store in a cool, dry place after opening.
This product is sold by weight not volume.
FDA Statement of Identity
A Dietary Supplement
General Statements
Amino acids Family owned since 1968.
Seals/Symbols
GMP Quality Assured
Triangle K (Kosher)
Is this label outdated? Report a formula or label change and our pharmacy team will review it.
L-Lysine 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 by NOW
This is the 1 active ingredient this product is made of. Select it to open its full monograph.
Serving size552 mg Dosage formPowder Servings per container822 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 & interactionsL-Lysine by NOW Drug Interactions
HelloPharmacist Interaction Report
L-Lysine by NOW is a single-ingredient supplement with one documented interaction.
The one medication type affected is 5-HT4 agonists (drugs that work through a specific serotonin pathway), which lysine may theoretically reduce the effects of. Animal research suggests lysine acts as a partial serotonin receptor 4 antagonist and blocks diarrhea caused by 5-HT4 agonist drugs, though human evidence is limited.
Read the full breakdown — every affected drug type, severity by severity
Alongside this minor interaction, no other drug types are documented as interacting with lysine in our data.
If you take any prescription medication, run it through the search tool on this page to check your exact drugs before starting this supplement.
Check your own medications below · Editorial policy · How we use AI
Want to check YOUR meds against L-Lysine?
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 interact with 1 drug. Click any drug to see the details.
1 of the 1 ingredient in L-Lysine interact with drugs. Each result below shows which ingredient is responsible. L-Lysine
TegaserodZelnorm
How Tegaserod interacts with L-Lysine — 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 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, 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 by NOW: Common Questions
Does L-Lysine by NOW interact with any medications?
How can one product interact with so many drugs?
Where does this information come from?
Does L-Lysine actually work for cold sores?
What are the side effects of L-Lysine?
Can I take L-Lysine while pregnant?
Is it safe to take L-Lysine while breastfeeding?
Why is L-Lysine used?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Not sure if L-Lysine 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’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'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