Last Editorial Review: 6/11/2021
Other Name(s):

Hydrochlorure de L-Lysine, L-2,6-diaminohexanoic acid, Lisina, L-Lysine, L-Lysine HCl, L-Lysine Hydrochloride, L-Lysine Monohydrochloride, Lys, Lysine Hydrochloride, Lysine Monohydrochloride, Monochlohydrate de L-Lysine, Monochlohydrate de Lysine.


Lysine is an amino acid (building block of protein). Unlike some other amino acids, the human body cannot make lysine; therefore it must be eaten in the diet. Sources of lysine include meat, fish, dairy, eggs, and some plants such as soy and other legumes.

Lysine is taken by mouth or applied directly to the skin for preventing and treating cold sores (caused by the virus called herpes simplex labialis).

Lysine is taken by mouth to improve athletic performance and for improving symptoms of schizophrenia. Lysine is also used to reduce symptoms of canker sores, and for diabetes, high triglyceride levels in the blood, muscle strength, stress, and a metabolic condition called metabolic alkalosis.

Lysine is applied to the skin for bed sores.

How does it work?

Lysine seems to prevent the herpes virus from growing.


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Uses & Effectiveness

Possibly Effective for...

  • Cold sores (herpes simplex labialis). Research suggests that lysine seems to reduce cold sores when taken by mouth and also when applied as a cream to the skin. Applying a specific product containing lysine, zinc oxide and 14 other ingredients (Super Lysine Plus +) seems to help reduce cold sores faster. However, some research suggests that lysine does not reduce the severity or recurrence of cold sores.

Insufficient Evidence to Rate Effectiveness for...

  • Canker sores. Early research suggests that taking 500 mg of lysine daily prevents canker sores and 4000 mg daily decreases the length of canker sores.
  • Diabetes. Some evidence shows that taking lysine twice daily for 2 months does not affect blood sugar levels in people with diabetes. However, other early research suggests that taking lysine twice daily for 2 months decreases blood sugar levels compared to before treatment in diabetes patients.
  • High triglyceride levels. Early research suggests that taking lysine daily for 12 weeks, with or without vitamin B6, does not affect body weight, triglyceride levels, or blood sugar levels in men with high triglycerides. Taking lysine might actually reduce high-density lipoprotein (HDL or "good") cholesterol levels.
  • Muscle strength. Early research suggests that consuming 80 mg/kg of lysine in the diet daily for 8 weeks improve muscle strength in the forearm by about 7.5% in young men.
  • Bed sores. Research suggests that applying a specific cream containing lysine (Lys-HA, Lysial, Fatai-Nyl Srl; Jasper LLC, Lugano, Switzerland) reduces bed sores in hospitalized adults. The cream seems to help patients with more severe bed sores better than minor ones.
  • Schizophrenia. Taking lysine by mouth seems to improve schizophrenia symptoms in some people taking antipsychotic drugs. Research suggests that taking lysine three times daily for 8 weeks improves symptoms by about 34% in people who are not fully responding to the drug risperidone.
  • Stress. Early research suggests that eating wheat that contains added lysine reduces stress in females and anxiety in males.
  • Improving athletic performance.
  • Metabolic condition involving pH of body tissues (metabolic alkalosis)..
More evidence is needed to rate the effectiveness of lysine for these uses.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).

Side Effects

Lysine is POSSIBLY SAFE for most people when taken by mouth at recommended doses for up to one year, or when applied to the skin short-term. It can cause side effects such as stomach pain and diarrhea.


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Special Precautions & Warnings

Pregnancy and breast-feeding: There is not enough reliable information about the safety of taking lysine if you are pregnant or breast feeding. Stay on the safe side and avoid use.

Kidney disease: There is one report of kidney disease linked with taking lysine supplements. If you have a kidney disease, check with your healthcare provider before taking lysine.

Osteoporosis: Using Lysine with calcium supplements might increase calcium absorption.

Intolerance to lysinuric protein: Lysine supplementation might cause diarrhea and stomach cramps in children who are intolerant to lysinuric protein.


Calcium supplementsInteraction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Lysine can increase how much calcium the body absorbs. Taking calcium along with lysine can increase the amount of calcium in the body. Avoid taking large amounts of calcium and lysine at the same time.

Gastrointestinal agents (5-HT4 agonist)Interaction Rating: Minor Be cautious with this combination.Talk with your health provider.

Lysine might inhibit the effects of some gastrointestinal agents including prucalopride and tegaserod.


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The following doses have been studied in scientific research:


  • For cold sores (herpes simplex labialis): 1000 mg of lysine taken daily in up to two divide doses for up to 12 months, or 1000 mg taken three times daily for 6 months has been used. For preventing cold sores from recurring, 500-1248 mg taken daily or 1000 mg taken three times daily has been used.
  • For treating cold sores (herpes simplex labialis): a specific combination of lysine plus zinc oxide and 14 other ingredients (Super Lysine Plus +) applied every 2 hours for 11 days has been used.

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