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Lysine Supplements

Read our review to find the best lysine (l-lysine) supplements, avoid pitfalls with labels, and learn whether lysine helps for cold sores (herpes simplex labialis), genital herpes lesions, and canker sores. Plus lysine dosage, safety and side-effect information. Find out which ones passed our tests and why.

Lysine Supplements Review

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CL Answer

Can any vitamins or minerals help prevent or reduce canker sores or cold sores?

Find out which, if any, supplements, including iron, L-lysine, monolaurin, olive leaf extract, vitamin B-12, and zinc, may be beneficial for canker sores or cold sores.

Lip of woman with a cold sore

News Release

August 31, 2023

Some L-Lysine Supplement Labels May Be Misleading, According to ConsumerLab Tests

White Plains, New York, August 31, 2023 —  Lysine (L-lysine) supplements may help prevent cold sores, genital herpes lesions, and canker sores, and are also promoted to slow hair loss, and treat herpes infections in cats.

CL Answer

Can beetroot juice or supplements lower blood pressure or improve exercise performance, and are they safe?

Learn more about beetroot juice and beetroot supplements and if beetroot can really help lower blood pressure.

Beetroot Juice for Lowering Blood Pressure? -- Glass of beetroot juice and blood pressure monitor

Clinical Update

1/16/2024

Lysine for Sleep?

Does taking lysine improve sleep? Find out in the What It Does section of our Lysine Supplements Review, which includes our Top Picks for L-lysine.

Also see: Which supplements and lifestyle changes improve sleep, and which cause insomnia?

CL Answer

What are human growth hormone (HGH) supplements? What are the benefits? Are they safe?

Learn about the benefits and risks of human growth hormone (HGH) supplements and injections. Get science-based insights on usage and effects.

Man at gym taking supplement

Clinical Update

11/08/2022

L-lysine For Hair?

Can supplementing with L-lysine help slow or reverse hair shedding? Find out what research suggests and who might benefit in our updated CL Answer about supplements for hair.

CL Answer

Which supplements can cause diarrhea?

Can supplements like magnesium cause diarrhea? Find out which supplements may cause diarrhea, such as vitamin B12, curcumin, magnesium, vitamin C and fish oil.

Which supplements can cause diarrhea? -- Woman with gastrointestinal pain

News Release

February 09, 2016

Lysine: Does It Work for Cold Sores and Which Brands Are Best? -- ConsumerLab.com Reviews the Evidence and Tests Supplements Often Used to Prevent Herpes Eruptions

White Plains, New York, February 9, 2016 — Lysine is an essential amino acid often taken as a supplement to prevent cold sores, genital herpes lesions, and canker sores. It's also given to cats with feline herpesvirus 1.

Product Review

Olive Leaf Extract Supplements Review

Learn What Olive Leaf Does and the Best Brands

CL Answer

Do any supplements help with COVID-19? Do supplements like vitamin D, zinc, vitamin C, or herbals work?

Find out if natural remedies & supplements for coronavirus such as zinc, vitamin C, garlic, or elderberry help to prevent or treat COVID-19.

Supplements for Coronavirus (COVID-19)? -- mask and pills

Clinical Update

7/20/2019

Zinc for Canker Sores?

We've added information about zinc to our answer to the question: Can lysine, vitamin B-12, or other vitamins or minerals help prevent or reduce canker sores?

Clinical Update

9/06/2023

Supplements for Cold Sores

Do lysine, monolaurin, or olive leaf extract help prevent or treat cold sores? Find out in our updated article about supplements for canker sores and cold sores.

Recalls & Warnings

August 14, 2023

Liver Injury Linked to "Immune Booster" Supplement Sold on Amazon

A 27-year-old woman in Pennsylvania was admitted to intensive care for drug-induced liver injury after taking Prodigy Life HRP-AID, a supplement sold on Amazon and promoted as an "immune system booster" to reduce the intensity and frequency of cold sore outbreaks, according to a ...

Product Review

Electrolytes & Sports Drinks Review

See Which Sports Drinks, Powders, and Pills Deliver the Right Electrolytes

Product Review

Lavender and Tea Tree Essential Oils Review

Oils Tested for Authenticity and Purity

Product Review

Lion's Mane and Chaga Supplements Review

Read Labels Carefully -- Many Can Mislead

Lion's Mane and Chaga Supplements tested by ConsumerLab.com

CL Answer

Can drinking coffee prevent gallstones? Can supplements help?

Information about the impact coffee has on gallstone disease. Plus, supplements that have been proposed to help with gallstone pain.

Coffee and Gallstones -- coffee in cup and coffee beans

Recalls & Warnings

December 31, 2020

FDA Warns Seller of Flu Immune

On December 21, 2020, the FDA issued a warning letter to Riverstone LLC for selling the products Flu Immune Drops, L-Lysine, Lysine Extra, and Monolaurin with unsupported claims that they can treat coronavirus (COVID-19).

CL Answer

Which supplements and lifestyle changes improve sleep, and which cause insomnia?

Find out which vitamins may help you sleep and learn if any vitamins or supplements can cause insomnia.

CL Answer

Do any supplements help prevent or reduce eye floaters?

Find out eye floaters (vitreous floaters) be treated with supplements like vitamin C, lutein, ginkgo, milk thistle, collagen or hyaluronic acid, or with products such as VitreousHealth.

How to Reduce Eye Floaters With Vitamins & Supplements -- Close-up of an eye

Recalls & Warnings

September 28, 2022

FDA Warns Muscle Sports for Joint Health, Immune & Workout Supplement, Vitamin C, Elderberry, and Other Claims

On September 23, 2022, the FDA issued a warning letter to Muscle Sports Products, LLC following inspection of the company’s websites which found statements about company products, including Join Revolution Capsules, IMMUNITY + Powder, Rhino Rampage PUMPED Capsules, Attack Pre-Workout ...

Recalls & Warnings

August 13, 2016

Seller of Omega-3, Ginkgo, Vision Supplements & More Warned for Drug Claims

On July 22, 2016, the FDA issued a warning letter to Viva Nutraceuticals (J & E International Corporation) following a review of the company's website and promotional literature, which found statement made about its products, Eyestonia, Ginkgo Biloba 60mg, Golden Omega-3 Max, ...

Recalls & Warnings

March 04, 2016

Federal Court Shuts Down Seller of Supplement Promoted for Herpes

On February 26, 2016, a federal court ordered dietary supplement company Viruxo LLC to stop selling its product Virux, which was promoted to treat herpes.

Recalls & Warnings

October 24, 2012

FDA Seizes Many Supplements from New York Company Due To Drug Claims

On October 23, 2012, U.S. Marshalls, acting on behalf of the FDA, seized dietary supplements and unapproved drugs from Confidence, Inc., a supplement manufacturer in Port Washington, N.Y. The products included dietary supplements Dr.

Recalls & Warnings

March 15, 2013

Maker of Liquid Supplements Warned For Manufacturing Violations and Drug Claims

On January 31, 2013, the FDA issued a warning letter to Liquid Health, Inc.

Recalls & Warnings

February 06, 2016

Seller of Turmeric, Milk Thistle and More Warned for Manufacturing Violations, Drug Claims

On January 15, 2016, the FDA issued a warning letter to Terra Firma Botanicals, Inc.

Recalls & Warnings

April 29, 2014

Seller of B Vitamins, CoQ10, Amino Acids and Other Supplements Warned for Manufacturing Violations and Drug Claims

On April 1, 2014, the FDA issued a warning letter to Bio-Recovery, Inc.

Recalls & Warnings

March 04, 2008

Airborne Settles Lawsuit Over False Advertising of its "Miracle Cold Buster"

On March 4, 3008, the Center for Science in the Public Interest (CSPI) announced that the makers of Airborne -- a multivitamin and herbal supplement whose labels and ads falsely claimed that the product cures and prevents colds -- will refund money to consumers who bought the product, as part of a ...