Lysine is an essential amino acid. The human body cannot make lysine, so it must be eaten in the diet. Sources include meat, fish, dairy, and eggs.

Lysine is a building block for making proteins in the body. It might also prevent the herpes virus from growing.

People use lysine for cold sores, canker sores, athletic performance, diabetes, and many other conditions, but there is no good scientific evidence to support most of these uses.
When taken by mouth: Lysine is possibly safe for most people when taken in doses up to 3000 mg daily for up to one year. It can cause side effects such as stomach pain and diarrhea.

When applied to the skin: Lysine is possibly safe for most people when used short-term.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if lysine is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Lysinuric protein intolerance: Lysine supplementation might cause diarrhea and stomach cramps in children who have this rare genetic disorder.


NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
Likely effective Effectiveness definitions
Possibly effective Effectiveness definitions
  • Cold sores (herpes labialis). Taking lysine by mouth might help prevent and heal cold sores. It's not clear if applying it to the skin helps.
There is interest in using lysine for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
Insufficient evidence Effectiveness definitions

Dosing & administration

Lysine has most often been used by adults in doses up to 3 grams daily for up to 1 year. It's also available in different topical products such as creams. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.

Interactions with pharmaceuticals

Gastrointestinal agents (5-HT4 agonist)

Interaction Rating=Minor Be watchful with this combination.

Lysine might reduce the effects of some gastrointestinal drugs called 5-HT4 agonists.

Interactions with herbs & supplements

Calcium: Lysine can increase how much calcium the body absorbs. This can increase the amount of calcium in the body. Taking lysine along with calcium might cause calcium levels to become too high.

Interactions with foods

There are no known interactions with foods.
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This monograph was last reviewed on 30/04/2023 10:00:00 and last updated on 31/10/2020 02:10:28. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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