Product Reviews
Lysine Supplements Review

Reviewed and edited by Tod Cooperman, M.D. Tod Cooperman, M.D.
Initial Posting: 2/6/16   Last Update: 4/7/20

Choose the Best Lysine Supplement

CL Tests Reveal Which Lysine Supplements Provide the Best Quality and Value

COVID-19 UPDATE: Lysine for Coronavirus?
Lysine supplement brands compared in this review
21st Century L-Lysine for Cats Nature Made L-Lysine Source Naturals L-Lysine
Andrew Lessman ProCaps Lysine Pet Naturals of Vermont L-Lysine for Cats Spring Valley [Walmart] L-Lysine
Carlson L-Lysine Puritan's Pride L-Lysine Swanson Free-Form L-Lysine
CVS/pharmacy L-Lysine Rexall L-Lysine Up & Up [Target] L-Lysine
Douglas Laboratories L-Lysine Rite Aid Pharmacy L-Lysine Vitacost L-Lysine
Finest Nutrition [Walgreens] L-Lysine Solaray L-Lysine Vitamin World L-Lysine
GNC L-Lysine Solgar L-Lysine  
21st Century L-Lysine for Cats Andrew Lessman ProCaps Lysine Carlson L-Lysine CVS/pharmacy L-Lysine Douglas Laboratories L-Lysine Finest Nutrition [Walgreens] L-Lysine GNC L-Lysine Nature Made L-Lysine Pet Naturals of Vermont L-Lysine for Cats Puritan's Pride L-Lysine Rexall L-Lysine Rite Aid Pharmacy L-Lysine Solaray L-Lysine Solgar L-Lysine Source Naturals L-Lysine Spring Valley [Walmart] L-Lysine Swanson Free-Form L-Lysine Up & Up [Target] L-Lysine Vitacost L-Lysine
Make sure the lysine supplement you take passed our quality review and is right for you!
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  • Lysine (L-lysine) is an essential amino acid found in many protein-rich foods (see Lysine in Food) and is needed for proper growth and other critical functions (see details in What It Is).
  • As a supplement, lysine may help prevent cold sores (herpes simplex labialis), genital herpes lesions, and canker sores. Although it is also found in topical products for cold sores, it is not known to be active topically (See details in What It Does).
    • COVID-19 UPDATE: Due to its potential antiviral and immune-stimulating properties, lysine is being promoted fight coronavirus (SARS-CoV-2) infection (COVID-19). However, there is no evidence at this time to suggest taking lysine supplements can help prevent or treat COVID-19. See the COVID-19 section section for details.
  • Typical daily dosage is 1,000 to 3,000 mg (see details in Quality Concerns).
  • Lysine has also been used to prevent/treat feline herpesvirus 1 infection — but there is no clinical evidence to support this use and it is not recommended (see details in What It Does, For Cats).
  • CL's tests found that all but one product contained their listed amounts of lysine (see details in What CL Found).
  • Best value: The cost to obtain lysine from CL Approved products ranged from 4 cents to 33 cents per 1,000 mg (and up to 72 cents for cat products). See which CL Approved products provide the best value.
  • To compare product test ratings, ingredients, and prices, see the Results Table.
  • People with kidney disease, gallstones, elevated cholesterol, and glutaric acidemia type I should exercise caution with lysine supplements (see details in Concerns and Cautions).
In this comprehensive review of lysine supplements, you'll get test results and quality ratings for 17 lysine supplements for people (including 7 that passed our voluntary Quality Certification Program) and two popular lysine supplements for cats. You'll also get information about an additional lysine supplement similar to one that passed testing. You'll learn:
    • Which lysine supplements passed or failed testing 
    • How lysine supplements compare on quality and cost and which provide the best value.
    • What lysine can and cannot do for your health, and your cat's health.
    • How to read the labels, so you know how much lysine you can really expect from a product without being fooled.  
    • Lysine dosage for uses including cold sores, genital herpes lesions and canker sores.
    • Concerns, drug interactions, and potential side-effects of lysine.

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Learn More About Lysine Supplements Answers -- for Lysine Supplements Review
Must I take amino acid supplements on an empty stomach? Can I take them with other amino acids or with food to help with swallowing capsules? Get the answer >>

Can lysine, vitamin B-12, or other vitamins or minerals help prevent or reduce canker sores? Get the answer >>

Which supplements can cause diarrhea? Get the answer >>
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