Herb & supplement monograph

Lysine Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Lysine interacts with medications. The heart of this page is the interaction list — every drug Lysine is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Lysine is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Reviewed by licensed pharmacists Sourced from Natural Medicines

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Lysine Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Lysine drug interaction appears very low for most people. Only a single interaction has been documented, it is rated minor, and it has not been shown to occur in humans.

Interactions deserving the most attention

The one recorded interaction involves 5-HT4 agonists, a class of medications that stimulate a specific serotonin receptor, often to help gut movement. Animal research suggests lysine may partly block that receptor and could, in theory, dull these drugs' effects. However, this finding is graded as unlikely, meaning it has appeared in lab or animal work but has not been shown to happen in people. So even this lone interaction is not a strong practical concern for most users.

What the rest of the list means

A short interaction list like this reflects how simply the body handles lysine, an amino acid it already uses every day. The single entry rests on animal research rather than human studies, so a meaningful effect on any medication has not been demonstrated. That makes lysine one of the less complicated supplements from a drug interaction standpoint.

Check your medications against Lysine

Based on HelloPharmacist’s Lysine interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Lysine

1 medication has a known interaction with Lysine, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Lysine using our pharmacist-reviewed interaction data.

AI summaries are generated from our Lysine interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Lysine combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Lysine affects

Every type of medication (drug category) Lysine is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 1 drug category Lysine interacts with

5-ht4 Agonists

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

Monograph

Lysine: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

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 the evidence is mixed and far from conclusive. For most healthy people who eat enough protein, supplements are likely unnecessary, but they are generally considered low-risk at typical doses.

Part used: Amino acid (L-lysine)
Common forms: Tablets, capsules, powder, topical creams (often combined with other ingredients)

People commonly use it for

Cold sores (herpes labialis)
Genital herpes outbreaks
Supporting protein and collagen formation
Calcium absorption support
General nutritional supplement

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Generally well tolerated at typical doses, but high amounts may cause stomach upset and long-term safety is not well studied.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Lysine (often sold as L-lysine) is an essential amino acid. Amino acids are the building blocks your body uses to make proteins. "Essential" means your body cannot make it on its own, so you must get it from food or supplements.

Lysine is found naturally in protein-rich foods such as meat, fish, eggs, dairy, soy, and legumes. Because of this, most people who eat a balanced diet get plenty of lysine without needing a supplement.

As a supplement, lysine is sold as tablets, capsules, powders, and topical creams. People most commonly take it in hopes of preventing or speeding the healing of cold sores caused by the herpes simplex virus.

How it works

As an amino acid, lysine is used by your body to build proteins, including those involved in making collagen, a structural protein in skin, bone, and connective tissue.

The proposed cold sore benefit is based on the idea that lysine may interfere with another amino acid called arginine, which the herpes virus seems to need to multiply. Some lab research suggests that more lysine and less arginine could slow the virus, but this mechanism has not been firmly proven to matter in real-world outbreaks.

Much of the reasoning about lysine comes from its basic nutritional role and from laboratory studies rather than large, high-quality human trials.

Effectiveness

Does Lysine work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 12 uses evaluated

1 Possibly effective 11 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

Possibly Effective Herpes labialis (cold sores)