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Dietary supplement

L-Lysine Ingredients & Drug Interactions

by Pure Encapsulations

L-Lysine label
See full label image
Capsule Category: Amino Acid/protein
Most serious interaction: Minor
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
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

The interaction bottom line Most serious interaction: Minor

L-Lysine is a dietary supplement by Pure Encapsulations 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 Hydrochloride. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against L-Lysine by Pure Encapsulations

Ask about any prescription or over-the-counter medication and we check it for interactions with L-Lysine by Pure Encapsulations — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of L-Lysine by Pure Encapsulations

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.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Aug 13, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains 1 active ingredient: L-lysine hydrochloride, an amino acid your body uses to build proteins and support immune function. The inactive ingredients are cellulose (a plant-based bulking agent), water, and ascorbyl palmitate (a form of vitamin C used as a preservative).

Does it work?

Moderate evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed

This product doesn't appear to be marketed for a specific use, so we graded Lysine's overall clinical evidence instead.

Moderate

Some clinical evidence supports Lysine for:

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.
  • Since the label doesn't commit to one use, we graded the ingredient's overall clinical evidence instead.
  • On file: Herpes labialis (cold sores) — rated "Possibly Effective" (Natural Medicines).

L-lysine is possibly effective for cold sores (herpes labialis) — meaning there's some evidence it may help, though more research would strengthen the case. For child growth, pressure ulcers, and diabetic foot ulcers, there isn't enough reliable evidence yet to know whether it works.

The evidence, ingredient by ingredient Lysine

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

L-lysine from food is safe. When taken as a supplement, it's generally well tolerated at typical doses, but high amounts may cause stomach upset, diarrhea, or indigestion.

Long-term safety from supplementation hasn't been thoroughly studied. Because safety during pregnancy and breastfeeding hasn't been well studied, talk with your doctor or pharmacist before using this supplement if you're pregnant or nursing.

Side effects, ingredient by ingredient Lysine

Meds to double-check

Minor interactions only
Known Interaction Concern · database check
Minor only

Only Minor-severity interactions are documented for these ingredients.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Lysine.
  • The most serious interaction on file is rated Minor.
  • For scale: 1 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

If you take a 5-HT4 agonist, let your doctor or pharmacist know before adding this supplement — lysine may reduce its effectiveness. For all other medications, no interactions are documented in our data, though that's not a guarantee none exist elsewhere.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence behind its ingredients' uses. Only minor medication interactions are documented, and safety information is well characterized.

L-lysine may help with cold sores if you're looking for a supplement option. If you take a 5-HT4 agonist (a gut-focused medication), check with your doctor or pharmacist first — this supplement might reduce how well it works.

For any other questions about whether it's right for you, talk it over with your own healthcare provider.

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 22, 2023.

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

At a glance

General information

Key facts about L-Lysine, straight from the product label.

Brand Pure Encapsulations
Barcode (UPC) 766298001685
Net contents 90 Capsule(s)
Market status On market
Date entered into DSLD Jun 22, 2023
DSLD ID 293997
Product type Amino Acid/protein
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Gluten Free
From the label
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 Pure Encapsulations, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Capsule(s)
Maximum serving Sizes:
1 Capsule(s)
Servings per container
90
UPC/BARCODE
766298001685
IngredientAmount% DV
L-Lysine Hydrochloride500 mg--

Other ingredients: Cellulose, Water, Ascorbyl Palmitate

Tap any ingredient to jump to its full detail below.

Label statements
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.
Storage

Store in a cool, dry place.

Suggested/Recommended/Usage/Directions

Recommendations: As a dietary supplement, take 1 capsule, 2 times daily, between meals, or as directed by a health professional.

Precautions

Warning: If you are pregnant or lactating, have any health condition or are taking any medication, consult your health professional before use.

Keep out of reach of children.

Use only if safety seal is intact.

General Statements

Contents may not fill package in order to accommodate required labeling. Please rely on stated quantity. Scan to learn about our hypoallergenic supplements

Seals/Symbols

GFCO.org (Gluten-Free Certification Organization)

Formulation

Certified gluten free by the Gluten-Free Certification Organization, www.gluten.org

Supports immune function

Gluten-free, non-GMO & hypoallergenic

Gluten-free, non-GMO & hypoallergenic

FDA Statement of Identity

Dietary Supplement

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.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

L-Lysine by Pure Encapsulations label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

L-Lysine label

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)
What’s inside

The Ingredients in L-Lysine by Pure Encapsulations

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size1 Capsule(s) Dosage formCapsule Servings per container90 Amounts shown are per serving.

L-Lysine Hydrochloride

Interacts with
1 drug
500 mg per serving

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 Hydrochloride monograph & interactions

Other (inactive) ingredients: Cellulose, Water, Ascorbyl Palmitate. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Lysine by Pure Encapsulations Drug Interactions

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 checker
1Drugs
1 Minor

Ingredients driving the most interactions

L-Lysine Hydrochloride 1

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 Hydrochloride

Each 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 Hydrochloride1 drug type · 1 drug

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.

Likelihood Unlikely Evidence D
L-Lysine Hydrochloride full monograph & interactions
The maker

Brand information

Manufacturer and brand details for L-Lysine, from the product label.

Pure Encapsulations

See all Pure Encapsulations products
Name
Pure Encapsulations
Street Address
490 Boston Post Road
City
Sudbury
State
MA
Phone Number
1-800-753-2277
Web Address
www.PureEncapsulations.com
Pharmacist Counseling Corner

L-Lysine by Pure Encapsulations: Common Questions

Does L-Lysine by Pure Encapsulations interact with any medications?
Yes. Based on its ingredients, L-Lysine has a known interaction with 1 medication. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
L-Lysine contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Does L-lysine actually work for cold sores?
It's possibly effective — meaning there's some evidence it may help, but the science isn't rock-solid yet. If you're thinking about trying it, talk with your doctor or pharmacist about whether it makes sense for you.
What side effects should I watch for?
Most people tolerate it well. At higher doses, some people report stomach upset, diarrhea, or indigestion. One rare case of kidney problems was reported with long-term use, though this is uncommon.
Is L-lysine safe to take while pregnant or breastfeeding?
The safety data on supplements isn't well studied in pregnancy and breastfeeding. Talk with your doctor or pharmacist before starting — they can weigh the pros and cons for your situation.
What is L-lysine and what does it do in my body?
It's an amino acid — a building block your body uses to make proteins and support your immune system. You get it from foods like meat, cheese, and eggs, and this supplement gives you a concentrated dose.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Not sure if L-Lysine is safe with your meds?

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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.

L-Lysine label
Go deeper

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.

Herb & supplement monograph

Lysine

Interacts with 1 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 try to prevent or shorten cold sores, but...

Read the full Lysine monograph →
Sources

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.

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
  1. 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
  2. McCune MA, Perry HO, Muller SA, O'Fallon WM. Treatment of recurrent herpes simplex infections with L-lysine monohydrochloride. Cutis 1984;34:366-73.
  3. DiGiovanna JJ, Blank H. Failure of lysine in frequently recurrent herpes simplex infection. Treatment and prophylaxis. Arch Dermatol 1984;120:48-51. DOI
  4. 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.
  5. 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
  6. 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
  7. 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.

See these in context on the Lysine monograph →

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

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