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Lysine (essential amino acid)

Written by Stephanie Nera, RPh, PharmD · Pharmacology

Updated Jan 25, 2021


Uses of lysine

Lysine is an essential amino acid. As an essential amino acid, it is required to be taken in through food or supplements. This is because the body does not naturally synthesize lysine. It plays an essential role in the production of carnitine, a nutrient responsible for converting fatty acids into energy, which helps to lower cholesterol. In addition, it lowers the amount of arginine necessary for herpes virus replication in cells and may improve calcium absorption.

How should I take lysine?


Lysine is available as an oral supplement. Therefore, it should be taken by mouth with a glass of water. It can be taken with or without meals.

Proper storage conditions

Store at room temperature, away from moisture and direct sunlight. To prevent drug damage, you should not store it in the bathroom or the freezer. There may be different brands of this drug that may have different storage needs. Therefore, it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush it down the toilet or pour them into a drain unless instructed to do so. Additionally, do not use it if expired. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using lysine?

Before taking this drug, tell your doctor if you:

  • Are currently pregnant or breastfeeding
  • Currently have high cholesterol or cardiovascular disease
  • Have liver or kidney impairment
  • Are currently taking any medications that contain arginine, lysine, or other amino acids
  • Have any history of allergy to other medications

Is it safe during pregnancy or breastfeeding?

There are no adequate studies in women for determining risk when using this drug during pregnancy or while breastfeeding. Therefore, always consult with your doctor to weigh the potential benefits and risks before taking lysine. Lysine is pregnancy risk category C according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk,
  • B=No risk in some studies,
  • C=There may be some risk,
  • D=Positive evidence of risk,
  • X=Contraindicated,
  • N=Unknown

Side effects

What are the side effects of lysine?

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. However, it can cause side effects such as stomach pain and diarrhea.

Rarely, large doses or chronic intake of lysine supplements may cause interstitial nephritis.

Not everyone experiences these side effects while some may experience side effects not mentioned here. If you have any concerns about side effects, please consult your doctor or pharmacist.


What drugs may interact with lysine?

Lysine may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

The use of calcium supplements with lysine may be associated with increased absorption and reduced elimination of calcium. Aminoglycoside toxicity may be enhanced in patients taking lysine supplementation. In addition, lysine may decrease the amount of arginine and vice versa.

Does food or alcohol interact with lysine?

Lysine may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist regarding any potential food or alcohol interactions before using this drug.

What health conditions may interact with lysine?

For patients with kidney problems, cardiovascular disease, or high cholesterol, lysine supplements may not be suitable. This may worsen your health condition or alter the way the drug works. However, because lysine is a necessary part of the human diet, it is impossible to completely avoid it. Therefore, it is important to always let your doctor and pharmacist know all the health conditions you currently have.


The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using this drug.

What is the dose for an adult?

Treatment and prophylaxis of herpes simplex

  • To treat symptoms: 3,000-9,000 mg/day, oral, in divided doses.
  • To prevent recurrences: 500-1,500 mg/day.

Dietary supplement

  • Oral: 500-1,000 mg/day.

What is the dose for a child?

There is no established pediatric dose. It may be unsafe for your child. Therefore, it is always important to consult with your doctor or pharmacist for more information.

How is lysine available?

Lysine is available in the following dosage forms and strengths:

  • Capsule, oral: 500 mg, 1000 mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.


Hello Health Group does not provide medical advice, diagnosis or treatment.

Written by

Stephanie Nera, RPh, PharmD


Updated Jan 25, 2021

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