Double Strength L-Lysine 1000 mg Ingredients & Drug Interactions
by NOW
What is this page for?
First and foremost: checking Double Strength 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
Double Strength L-Lysine 1000 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 Double Strength L-Lysine 1000 mg by NOW
Ask about any prescription or over-the-counter medication and we check it for interactions with Double Strength L-Lysine 1000 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 Double Strength L-Lysine 1000 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 contains one active ingredient: L-lysine hydrochloride at 1000 mg per tablet. Lysine is an amino acid — one of the building blocks your body uses to make protein.
The tablet also contains several inactive ingredients (microcrystalline cellulose, silicon dioxide, stearic acid, a vegetarian coating, croscarmellose sodium, and magnesium stearate), which are fillers, binders, and capsule materials that have no active effect.
Does it work?
Moderate evidence
L-lysine is possibly effective for cold sores (herpes labialis) — meaning there's some evidence it may help, but it's not conclusive. The evidence for child growth, pressure ulcers, and diabetic foot ulcers isn't established in the data we hold, so we can't tell you whether it works for those 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 hasn't been thoroughly studied.
The most common side effects reported are abdominal pain, diarrhea, and indigestion. There is one case report of oral lysine linked to a serious kidney condition, though this is extremely rare.
For pregnancy, supplement safety isn't well studied — lysine from food is fine, but check with your doctor before taking it as a supplement. For breastfeeding, there isn't enough reliable information, so caution is advised — talk with your pharmacist or doctor.
Meds to double-check
Minor interactions only
5-HT4 agonists (medications that boost gut motility) — lysine may reduce their effects. If you take one of these, let us check it with you before you start this supplement.
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 getting cold sores, L-lysine may be worth a try — the evidence suggests it could help. If you take a 5-HT4 agonist or any other prescription medication, check it with us first.
If you're pregnant or breastfeeding, ask 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 Jun 20, 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 Double Strength L-Lysine 1000 mg, straight from the product label.
| Brand | NOW |
|---|---|
| Barcode (UPC) | 733739001238 |
| Net contents | 250 Tablet(s) |
| Market status | On market |
| Date entered into DSLD | Jun 20, 2024 |
| DSLD ID | 314283 |
| 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, Halal, Gluten 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 Double Strength L-Lysine 1000 mg by NOW, sourced from the NIH Dietary Supplement Label Database.
Supplement Facts
| Ingredient | Amount | % DV |
|---|---|---|
| L-Lysine Hydrochloride | 1270 mg | -- |
| L-Lysine | 1 Gram(s) | -- |
Other ingredients: Microcrystalline Cellulose, Silicon Dioxide, Stearic Acid, Vegetarian Coating, Croscarmellose Sodium, 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 2 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.
Essential amino acid
Triangle K (Kosher)
This product has twice the L-Lysine (1,000 mg per tablet) as in our regular strength product (500 mg per tablet).
NOW L-Lysine is a Pharmaceutical Grade essential amino acid.
Crescent H (Halal)
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 or tree nut ingredients. Produced in a GMP facility that processes other ingredients containing these allergens.
Formulation
Natural color variation may occur in this product.
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 or tree nut ingredients.
Storage
Store in a cool, dry place after opening.
FDA Statement of Identity
A Dietary Supplement
Seals/Symbols
Triangle K (Kosher)
Crescent H (Halal) GMP Quality Assured
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.
Double Strength L-Lysine 1000 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 Double Strength L-Lysine 1000 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, Silicon Dioxide, Stearic Acid, Vegetarian Coating, Croscarmellose Sodium, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.
Double Strength L-Lysine 1000 mg by NOW Drug Interactions
HelloPharmacist Interaction Report
NOW's Double Strength L-Lysine 1000 mg contains one active ingredient — L-lysine hydrochloride — which has one documented interaction.
L-lysine may theoretically reduce the effects of 5-HT4 agonists (medications that boost serotonin signaling in the gut, sometimes used for stomach motility). Animal research suggests lysine blocks this receptor, though the clinical importance in people isn't yet clear.
This is a Minor interaction, meaning the effect is usually small.
Read the full breakdown — every affected drug type, severity by severity
Altogether, these interactions span 1 individual medication.
Before you start, run your exact medications through the search tool on this page. If you take a 5-HT4 agonist or any other prescription drug, let us know so we can check it for you.
Check your own medications below · Editorial policy · How we use AI
Want to check YOUR meds against Double Strength 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 Double Strength L-Lysine 1000 mg interact with 1 drug. Click any drug to see the details.
1 of the 1 ingredient in Double Strength L-Lysine 1000 mg interact with drugs. Each result below shows which ingredient is responsible. L-Lysine
TegaserodZelnorm
How Tegaserod interacts with Double Strength 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 Double Strength 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 Double Strength L-Lysine 1000 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
Double Strength L-Lysine 1000 mg by NOW: Common Questions
Does Double Strength L-Lysine 1000 mg by NOW interact with any medications?
How can one product interact with so many drugs?
Where does this information come from?
Will L-lysine help my cold sores?
What side effects does L-lysine cause?
Is L-lysine safe to take if I'm pregnant?
Can I take L-lysine while breastfeeding?
What's L-lysine and why would I take it?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Not sure if Double Strength 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 Double Strength 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
Double Strength 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