Medically Reviewed on 4/21/2022

Generic Name: lysine

Brand and Other Names: L-lysine, lysine monohydrochloride

Drug Class: Herbals

What is lysine, and what is it used for?

Lysine is an essential amino acid, a building block of proteins, and is involved in many biological processes in the body. Essential amino acids are necessary for human health, but are not synthesized in the body and must be obtained from the diet.

Lysine is used to treat cold sores (herpes simplex labialis), increase alkalinity in the body (metabolic alkalosis), improve bone density, and boost athletic performance.

Lysine plays a vital role in many processes including:

  • Synthesis of carnitine, a compound that is involved in converting fatty acids into energy
  • Absorption of calcium
  • Formation of collagen, the protein in bone and connective tissue such as skin, cartilage, and tendons
  • Production of antibodies, hormones, and enzymes

Herpes simplex viral proteins are rich in arginine, another amino acid, which promotes viral replication. Lysine inhibits viral replication by blocking the activity of arginine because it uses the same pathways as arginine. Studies show that regular intake of lysine may prevent cold sore outbreaks, or reduce their frequency and severity, but may not improve the healing of sores.

Lysine lowers the pH levels in the body and restores acid-base balance in metabolic alkalosis. Some studies suggest lysine may help muscle tissue recovery and some athletes use it as a protein supplement. Lysine helps calcium absorption, but there aren’t any studies that support its use in preventing bone loss (osteoporosis).

Good dietary sources of lysine include animal products including red meats, pork and poultry, eggs, cheese, and other dairy products, and certain types of fish such as cod and sardine. Vegetable sources include soy, legumes, spirulina, and fenugreek seeds. Lysine supplements are available as oral tablets and capsules, and topical formulations.

Suggested uses of lysine include:

  • Herpes simplex labialis caused by the herpes simplex virus type-1 (HSV-1)
  • Metabolic alkalosis
  • Enhancement of athletic performance


  • Use lysine with caution if you are taking calcium supplements; lysine increases calcium absorption
  • Excessive doses of lysine may cause gallstones and kidney disorders
  • Avoid lysine supplementation in children with lysinuric protein intolerance, a rare genetic disorder that causes inability to digest certain amino acids including lysine

What are the side effects of lysine?

Common side effects of lysine include:

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug.

Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

What are the dosages of lysine?

Dosage varies; consult specific product information.

Suggested Dosage:

Herpes Simplex Labialis

  • 1,000 mg orally once to three times daily for 6-12 months
  • Topical: (Super Lysine Plus) applied every 2 hours for 11 days

Metabolic Alkalosis

  • 10 grams orally once daily, divided doses for up to 5 days


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What drugs interact with lysine?

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

  • Enhance absorption of calcium supplements
  • Lysine may reduce the effects of some gastrointestinal drugs known as 5-HT4 agonists.
  • Concurrent use with aminoglycoside antibiotics such as gentamicin, neomycin, and streptomycin may increase the risk of toxicity to the kidney.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

Pregnancy and breastfeeding

  • Lysine is an essential amino acid and studies suggest that daily requirement goes up during pregnancy.
  • Lysine crosses the placenta and is present in breast milk. There is, however, insufficient research on safety of lysine use during pregnancy and breastfeeding.
  • It is safer to get adequate lysine through dietary intake and avoid lysine supplementation.


  • There is not much research on how much lysine one should take and the effects of overdose.
  • Lysine overdose may cause stomach pain and diarrhea. In case of overdose, seek medical help or contact Poison Control.

What else should I know about lysine?

  • Lysine is generally safe in recommended doses, however, it is ideally obtained from dietary sources.
  • Lysine cannot take the place of medications; do not take it instead of prescribed medications.
  • Lysine is marketed as a supplement and is not as stringently regulated by the FDA as prescription drugs are; exercise caution.


Lysine is an essential amino acid used to treat cold sores (herpes simplex labialis), increase alkalinity in the body (metabolic alkalosis), improve bone density, and boost athletic performance. Lysine increases calcium absorption. Excessive doses may cause gallstones and kidney disorders. Common side effects of lysine include abdominal pain, diarrhea, kidney inflammation (interstitial nephritis), and chronic kidney (renal) failure. It is safer to get adequate lysine through dietary intake and avoid lysine supplementation during pregnancy and when breastfeeding.

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You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Medically Reviewed on 4/21/2022