L-Lysine 1000 mg Ingredients & Drug Interactions
by 21st Century
What is this page for?
First and foremost: checking L-Lysine 1000 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 1000 mg is a dietary supplement by 21st Century 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 1000 mg by 21st Century
Ask about any prescription or over-the-counter medication and we check it for interactions with L-Lysine 1000 mg by 21st Century — 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 1000 mg by 21st Century
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 supplement contains one active ingredient: L-lysine, an amino acid your body uses to build and repair tissues, particularly in skin and connective tissue. The rest of the tablet is made up of inactive ingredients (cellulose, stearic acid, croscarmellose sodium, magnesium silicate, magnesium stearate, polyethylene glycol, polyvinyl alcohol, silicon dioxide, and titanium dioxide) — these are fillers and binders that hold the tablet together.
Does it work?
Moderate evidence
L-lysine is possibly effective for cold sores (herpes labialis). For other uses listed in the research — child growth, pressure ulcers, and diabetic foot ulcers — the evidence isn't reliable enough for us to rate it one way or the other.
How safe is it?
Well-documented data
Lysine is generally well tolerated at typical doses. At high amounts, it may cause stomach upset like abdominal pain, diarrhea, or indigestion.
Long-term safety at high doses hasn't been well studied. For pregnancy, supplement safety hasn't been well studied either — food sources of lysine are fine, but check with your doctor before taking a supplement.
There isn't enough reliable information on supplement use while breastfeeding, so caution is advised and a conversation with your doctor or pharmacist is wise.
Meds to double-check
Minor interactions only
If you take a 5-HT4 agonist (a medication that speeds up stomach or bowel movement), let your doctor or pharmacist know before adding this supplement — lysine may reduce how well it works.
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.
If you're looking to manage cold sores, lysine may help — the evidence suggests it's possibly effective. It's generally well tolerated, though high doses can upset your stomach.
If you're pregnant, breastfeeding, or take medications for digestive motility, talk it over with your doctor or pharmacist before starting.
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 Jan 24, 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 1000 mg, straight from the product label.
| Brand | 21st Century |
|---|---|
| Barcode (UPC) | 740985280638 |
| Net contents | 90 Tablet(s) |
| Market status | On market |
| Date entered into DSLD | Jan 24, 2024 |
| DSLD ID | 304110 |
| 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), 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 1000 mg by 21st Century, sourced from the NIH Dietary Supplement Label Database.
Supplement Facts
| Ingredient | Amount | % DV |
|---|---|---|
| L-Lysine | 1000 mg | -- |
Other ingredients: Cellulose, Stearic Acid, Croscarmellose Sodium, Magnesium Silicate, Magnesium Stearate, Polyethylene Glycol, Polyvinyl Alcohol, Silicon Dioxide, Titanium Dioxide
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.
Formula
L-Lysine is an essential amino acid which must be supplied rom nutritional sources and is a building block of protein.
Suggested/Recommended/Usage/Directions
Directions: As a dietary supplement, adults take one (1) tablets daily with any meal or as directed by a healthcare provider.
Precautions
Do not exceed recommended dosage. Individual results may vary.
Warning: Consult a healthcare provider prior to use if pregnant, nursing, on medications, have a medical condition or are planning a medical procedure.
Stop use and contact a physician if adverse reactions occur. Do not use if product appears to be tampered with or seal is broken.
Keep out of reach of children.
Storage
Store at room temperature.
Formulation
No added sugar, yeast, preservatives or artificial flavors.
Suitable for vegans.
Actual size
Skin & tissue support
Gluten free Non-GMO
Guaranteed quality Laboratory tested Trusted quality for over 30 years
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.
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 1000 mg by 21st Century 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 1000 mg by 21st Century
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 container90 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: Cellulose, Stearic Acid, Croscarmellose Sodium, Magnesium Silicate, Magnesium Stearate, Polyethylene Glycol, Polyvinyl Alcohol, Silicon Dioxide, Titanium Dioxide. These complete the product’s ingredient list but are not active constituents.
L-Lysine 1000 mg by 21st Century Drug Interactions
HelloPharmacist Interaction Report
L-Lysine 1000 mg by 21st Century has one documented interaction.
Through its lysine content, it may reduce the effects of 5-HT4 agonists (a class of medications used to treat certain digestive issues). Animal research suggests lysine acts as a partial blocker of the serotonin receptor 4, which could theoretically dampen how these drugs work.
Read the full breakdown — every affected drug type, severity by severity
Alternate serotonin or motility agents you take should be reviewed with your doctor or pharmacist before starting this supplement, since the reduced drug effect could matter for your treatment. Altogether, these interactions span 1 individual medication.
Check your own medications below · Editorial policy · How we use AI
Want to check YOUR meds against L-Lysine 1000 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 1000 mg interact with 1 drug. Click any drug to see the details.
1 of the 1 ingredient in L-Lysine 1000 mg interact with drugs. Each result below shows which ingredient is responsible. L-Lysine
TegaserodZelnorm
How Tegaserod interacts with L-Lysine 1000 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 1000 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 1000 mg, from the product label.
21st Century
See all 21st Century products- Name
- 21st Century HealthCare, Inc.
- Street Address
- 2119 S. Wilson St.
- City
- Tempe
- State
- AZ
- ZipCode
- 85282
- Web Address
- 21stcenturyvitamins.com
L-Lysine 1000 mg by 21st Century: Common Questions
Does L-Lysine 1000 mg by 21st Century interact with any medications?
How can one product interact with so many drugs?
Where does this information come from?
Will L-lysine help me get rid of my cold sores?
What are the side effects?
Is it safe to take while pregnant?
Can I take it while breastfeeding?
What other uses does L-lysine have?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Not sure if L-Lysine 1000 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 1000 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 1000 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