Lysine is an essential amino acid needed for growth and to help maintain nitrogen balance in the body. (Essential amino acids cannot be made in the body and must be supplied by the diet or supplements.)

What Are Star Ratings?

This supplement has been used in connection with the following health conditions:

Used forWhy
3 Stars
Cold Sores
1 to 3 grams daily
Supplementing with lysine may reduce recurrences by suppressing the virus that causes sores.

The amino acid has been reported to reduce the recurrence rate of herpes simplex infections in both preliminary and double-blind trials. The amount used in these studies was usually 1 to 3 grams per day, although some people received as little as 312 mg per day. In one double-blind trial, lysine supplementation (1,200 mg per day) failed to prevent recurrences better than placebo. However, the results of that study may have been skewed by a large number of dropouts in the placebo group who fared poorly but were not included in the analysis.

When lysine has been used for acute outbreaks, the results have been mixed. In a preliminary study, 390 mg of lysine taken at the first sign of a herpes outbreak resulted in rapid resolution of the cold sores in all cases. However, in a double-blind study, supplementing with 1 gram of lysine per day for five days did not increase the healing rate of the cold sores.

2 Stars
Genital Herpes
1,000 mg daily
Taking lysine may speed healing and help prevent future outbreaks.

Most research on has been done on people with cold sores or on groups that include both cold sores and genital herpes sufferers. However, some evidence exists that supplemental lysine may be effective in the prevention and treatment of genital herpes. In one preliminary survey, 81% of people with HSV infections (including genital herpes) reported lysine was effective for reducing recurrences and shortening healing time in amounts averaging about 1,000 mg per day. A small double-blind trial of people with oral and genital herpes examined the effects of 1,248 mg or 624 mg of lysine daily versus placebo. The study found that 1,248 mg per day of lysine, but not the lower dose, was effective in reducing the recurrence rate of herpes outbreaks by 57% to 65%, while neither dose helped reduce the healing time. Another small double-blind trial found that using 3,000 mg per day of lysine in divided doses led to a decrease in severity of symptoms and a reduction in healing time of both oral and genital herpes. One preliminary report found no benefit of lysine for a group of patients with either oral or genital herpes.

1 Star
Shingles and Postherpetic Neuralgia
Refer to label instructions
Because shingles is caused by a herpes virus, some doctors believe that lysine could help, since it inhibits replication of herpes simplex, a related virus.

Because shingles is caused by a herpes virus, some doctors believe that supplementation could help people with the condition, since lysine inhibits replication of herpes simplex, a related virus. However, lysine has not been shown to inhibit Varicella zoster, nor has it been shown to provide any benefit for people with shingles outbreaks. Therefore, its use in this condition remains speculative.

How It Works

How to Use It

Most people do not require lysine supplementation. Doctors often suggest that people with recurrent herpes simplex infections take 1,000–3,000 mg of lysine per day.

Where to Find It

Brewer’s yeast, legumes, dairy, fish, and meat all contain significant amounts of lysine.

Possible Deficiencies

Most people, including vegans (vegetarians who also avoid dairy and eggs), consume adequate amounts of lysine. However, vegans whose diets contain large amounts of grains and only minimal amounts of beans could become deficient in lysine. Athletes involved in frequent vigorous exercise have increased need for essential amino acids, although most diets meet these increased needs. The essential amino acid requirements of burn patients may exceed the amount of lysine in the diet.


Interactions with Supplements, Foods, & Other Compounds

Lysine supplementation increases the absorption of calcium and may reduce its excretion.1 As a result, some researchers believe that lysine may eventually be shown to have a role in the prevention and treatment of osteoporosis.2

Lysine works with other essential amino acids to maintain growth, lean body mass, and the body’s store of nitrogen.

Interactions with Medicines

As of the last update, we found no reported interactions between this supplement and medicines. It is possible that unknown interactions exist. If you take medication, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.

Side Effects

Side Effects

In animals, high amounts of lysine have been linked to increased risk of gallstones3 and elevated cholesterol.4 At supplemental amounts, no consistent problems have been reported in humans, though abdominal cramps and transient diarrhea have occasionally been reported at very high (15–40 grams per day) intakes.5


1. Civitelli R, Villareal DT, Agnusdei D, et al. Dietary L-lysine and calcium metabolism in humans. Nutrition 1992;8:400-5.

2. Flodin NW. The metabolic roles, pharmacology, and toxicology of lysine. J Am Coll Nutr 1997;16:7-21 [review].

3. Kritchevsky D, Weber MM, Klurfeld DM. Gallstone formation in hamsters: influence of specific amino acids. Nutr Rep Int 1984;29:117.

4. Leszczynski DE, Kummerow FA. Excess dietary lysine induces hypercholesterolemia in chickens. Experientia 1982;38:266-7.

5. Flodin NW. The metabolic roles, pharmacology, and toxicology of lysine. J Am Coll Nutr 1997;16:7-21 [review].

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