uses JavaScript to provide the best possible experience for our content, but your browser has it disabled. Learn how to enable it here.


Last Updated: 04/07/2020 |

Lysine supplement brands compared in this review


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

Vitamin World L-Lysine

Make sure the lysine supplement you take passed our quality review and is right for you!
Isn't your health worth it?

See the Review Now

Join now at


  • What is lysine? 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).
  • What are the health benefits of lysine? 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).
  • How much lysine to take? 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).
  • What did CL's tests of lysine find? CL's tests found that all but one product contained their listed amounts of lysine (see details in What CL Found).
  • Best value for lysine: 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.
  • Lysine safety and side effects: 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.

Join to unlock the full report and get full access to over 1,300 reviews

See the Review Now

Join now at