L-Lysine HCL Ingredients & Drug Interactions
by Priority One Nutritional Supplements
What is this page for?
First and foremost: checking L-Lysine HCL 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 HCL is a dietary supplement by Priority One Nutritional Supplements 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.
Check Your Meds Against L-Lysine HCL by Priority One Nutritional Supplements
Ask about any prescription or over-the-counter medication and we check it for interactions with L-Lysine HCL by Priority One Nutritional Supplements — 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 HCL by Priority One Nutritional Supplements
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, an amino acid your body uses for protein building and immune function. The capsule also holds silicon dioxide (an inert flow agent) and is made from vegetarian cellulose.
Does it work?
Moderate evidence
The evidence here is mixed. L-lysine is possibly effective for cold sores (herpes labialis) — the research suggests it may help if you take it regularly.
For other uses like supporting child growth, pressure ulcers, or diabetic foot ulcers, we don't have enough reliable evidence to say whether it works.
How safe is it?
Well-documented data
Lysine from food is safe, and the supplement is generally well tolerated at typical doses. High amounts may cause stomach upset, and long-term safety hasn't been thoroughly studied.
During pregnancy, the safety data on lysine supplements isn't established — talk with your doctor first. For breastfeeding, there isn't enough reliable information either, so caution is advised and you should check with your doctor or pharmacist.
There's also one rare case report of a person who developed kidney problems linked to high-dose oral lysine, though this is uncommon.
Meds to double-check
Minor interactions only
If you take a 5-HT4 agonist (a medication for certain digestive conditions), check with your doctor or pharmacist before adding L-lysine — it may reduce how well the drug works. For all other medications, no interactions are documented in our data.
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 option if you're looking for support with cold sores, where the evidence leans toward it being possibly effective. If you take a 5-HT4 agonist, check with your doctor or pharmacist before starting.
Pregnant or breastfeeding? Talk it over with your healthcare provider first, since the safety data isn't complete.
For any other questions about whether it's right for you, your doctor or pharmacist can help.
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 Oct 23, 2020.
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 HCL, straight from the product label.
| Brand | Priority One Nutritional Supplements |
|---|---|
| Barcode (UPC) | 815354020822 |
| Net contents | 60 Vegetarian Capsule(s) |
| Market status | On market |
| Date entered into DSLD | Oct 23, 2020 |
| DSLD ID | 236797 |
| Product type | Amino Acid/protein |
| Supplement form | Capsule |
| Dietary claims / uses | All Other, Structure/Function |
| Intended target group(s) | Vegetarian, Adult (18 - 50 Years) |
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 HCL by Priority One Nutritional Supplements, sourced from the NIH Dietary Supplement Label Database.
Supplement Facts
| Ingredient | Amount | % DV |
|---|---|---|
| L-Lysine Hydrochloride | 500 mg | -- |
Other ingredients: Silicon Dioxide, Vegetarian Capsule
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.
Precautions
Warning: If you are pregnant or breast feeding consult your physician before using this product.
Keep out of reach of children.
Suggested/Recommended/Usage/Directions
Recommendations: Take (1) one capsule four times daily or as directed by a physician.
Storage
Keep container tightly closed, store in a cool, dry place.
Formulation
Contains no preservatives.
Vegetarian formulation
Non-GMO
General Statements
Bisphenol-A (BPA) & Phthalate Free
Priority One Nutritional Supplements Inc since 1988
For professional use only.
Seals/Symbols
GMP Certified
FDA Statement of Identity
A Dietary Supplement
FDA Disclaimer Statement
This statement has not been evaluated by the FDA. 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.
L-Lysine HCL by Priority One Nutritional Supplements 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 HCL by Priority One Nutritional Supplements
This is the 1 active ingredient this product is made of. Select it to open its full monograph.
Serving size1 Vegetarian Capsule(s) Dosage formCapsule Amounts shown are per serving.
L-Lysine Hydrochloride
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 Hydrochloride monograph & interactionsOther (inactive) ingredients: Silicon Dioxide, Vegetarian Capsule. These complete the product’s ingredient list but are not active constituents.
L-Lysine HCL by Priority One Nutritional Supplements Drug Interactions
HelloPharmacist Interaction Report
L-Lysine HCL by Priority One Nutritional Supplements has one documented interaction: it may reduce the effects of 5-HT4 agonists (a drug class used for certain gastrointestinal conditions).
Animal research suggests lysine acts as a partial blocker of the serotonin receptor that these drugs target, which could weaken their ability to work.
Read the full breakdown — every affected drug type, severity by severity
This is a Minor interaction, so it's not an immediate danger — but if you take a 5-HT4 agonist, it's worth a conversation with your doctor or pharmacist before starting lysine. Altogether, this interaction spans 1 individual medication.
Check your own medications below · Editorial policy · How we use AI
Want to check YOUR meds against L-Lysine HCL?
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 HCL interact with 1 drug. Click any drug to see the details.
1 of the 1 ingredient in L-Lysine HCL interact with drugs. Each result below shows which ingredient is responsible. L-Lysine Hydrochloride
TegaserodZelnorm
How Tegaserod interacts with L-Lysine HCL — through 1 ingredient. Tap an ingredient for the detail:
L-lysine Hydrochloride5-ht4 Agonists Minor
Interaction Summary
Theoretically, lysine may reduce the effects of 5-HT4 agonists.
Read the full L-lysine Hydrochloride + Tegaserod interactionEach ingredient & the kinds of drugs it affects
For each ingredient in L-Lysine HCL 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 Hydrochloride
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 HCL, from the product label.
Priority One Nutritional Supplements
See all Priority One Nutritional Supplements products- Name
- Priority One Nutritional Supplements, Inc.
L-Lysine HCL by Priority One Nutritional Supplements: Common Questions
Does L-Lysine HCL by Priority One Nutritional Supplements 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 should I watch for?
Is it safe to take while pregnant?
Can I take it while breastfeeding?
How much can I safely take?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Not sure if L-Lysine HCL 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 HCL’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 HCL'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