Initially Posted: 02/01/2016 | Last Updated: 09/12/2020

Lysine supplement brands compared in this review

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21st Century L-Lysine for Cats

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Andrew Lessman ProCaps Lysine

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Carlson L-Lysine

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CVS/pharmacy L-Lysine

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Douglas Laboratories L-Lysine

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Finest Nutrition [Walgreens] L-Lysine

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GNC L-Lysine

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Nature Made L-Lysine

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Pet Naturals of Vermont L-Lysine for Cats

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Puritan's Pride L-Lysine

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Rexall L-Lysine

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Rite Aid Pharmacy L-Lysine

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Solaray L-Lysine

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Solgar L-Lysine

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Source Naturals L-Lysine

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Spring Valley [Walmart] L-Lysine

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Swanson Free-Form L-Lysine

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Up & Up [Target] L-Lysine

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Vitacost L-Lysine

Vitamin World L-Lysine

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Summary

  • 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).
  • 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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