What Is Lysine?

Can lysine help to heal cold sores?

Lysine capsules, tablets, beans, eggs, and nuts

Verywell / Anastasia Tretiak

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Lysine is an essential amino acid. Your body uses amino acids to make proteins, but it can't produce its own essential amino acids. You have to get them from diet or supplements.

Lysine is thought to help the body produce infection-fighting antibodies, enzymes, hormones, and body tissues. Lysine is found in high-protein foods like meat, nuts, beans, eggs, and soy.

Lysine supplements are also known as "L-lysine." They are sold as a natural remedy for a number of health problems. Some lysine supplements contain a combination of lysine and L-arginine, another essential amino acid.

This article will discuss some of the uses of lysine supplements and topical lysine. It will also discuss dosage, side effects, and some things you should look for when buying lysine supplements and ointments.

What Is Lysine Used For?

Lysine supplements are used to treat a wide range of conditions, including:

Proponents say lysine supplements can boost the immune system. They are also used to aid in muscle repair and improve muscle strength.

So far, there is not enough clinical evidence to support most of these uses.

A few studies suggest that lysine supplements can be used to treat certain health conditions. Here's a look at some key study findings.

Cold Sores

Some studies suggest lysine supplements may reduce the severity and duration of cold sore outbreaks. This may be because lysine keeps herpes simplex, the virus that causes cold sores, from reproducing.

A 2017 review, however, concluded there was not enough evidence to support the use of lysine supplements for preventing cold sore outbreaks.

In 2015, researchers reviewed a number of trials of different interventions for preventing cold sores. They also did not find any evidence that lysine was effective for this.

Other research has explored topical lysine as a treatment for herpes simplex infections.

In a 2005 study of 30 patients, scientists found that cold sores cleared up in 40% of participants after three days of using a lysine- and zinc oxide-based ointment. By the sixth day, cold sore symptoms were resolved in 87% of patients.

However, the study didn't have an untreated control group to compare the results to. Left untreated, cold sores may last up to 21 days.


More research is needed, but a few studies have found that a combination of l-lysine and l-arginine may help reduce anxiety. Researchers think one of the reasons this might work is because l-lysine and l-arginine help lower cortisol levels. Cortisol is your body's primary stress hormone.


Preliminary research suggests that lysine supplements may help the body absorb calcium. This might help protect against bone loss.

Scientists have yet to confirm that lysine supplements help prevent osteoporosis in humans, though.


A few studies suggest that lysine may help cold sores. It may also help anxiety and improve calcium absorption. More research is needed to confirm these findings.

Possible Side Effects

Lysine supplements are probably safe for most people. Oral lysine can be taken for up to one year in appropriate doses. Topical lysine can also be used for up to a year. Side effects can include stomach pain and diarrhea.

Certain people should avoid lysine supplements. There is not enough evidence to know if it is safe for people who are pregnant or breastfeeding. People with kidney disease, lysinuric protein intolerance (a condition in which the body can't use lysine and other amino acids), or osteoporosis should ask a doctor before taking lysine.

Eggs, nuts, and beans
Verywell / Anastasia Tretiak

Dosage and Preparation

Most people can get enough lysine by following a balanced diet containing high-protein foods. There is no standard recommended dose for lysine as a supplement or for topical use.

Different doses have been used in research. For cold sores, studies have used doses of 500-1248 mg daily or 1000 mg three times daily. Doses applied to the skin vary.

If you want to use lysine supplements to treat or prevent a specific health problem, ask your doctor first. They can help you find the right dose and provide instructions for use.


Lysine supplements are probably safe for most people, but talk to your doctor before using.

What to Look For

The National Institutes of Health (NIH) recommends checking the supplement facts label before buying any dietary or herbal supplement, including lysine. This label provides important information about the amount of active ingredient per serving. It should also include information about other ingredients.

The NIH also recommends looking for a product that has been quality tested by an independent organization. Most supplements that have been quality tested will include these details in the product information.

Quality testing organizations include:

  • U.S. Pharmacopeia
  • ConsumerLab.com
  • NSF International

A seal of approval from one of these organizations helps you know that the product was properly manufactured, contains the listed ingredients, and does not include harmful levels of contaminants. It does not, however, guarantee the product's safety or effectiveness.


Make sure to read the label before you purchase any supplement. Look for supplements that have been quality tested by a third party.


Lysine is an important amino acid that can be found in high-protein foods like meat, nuts, beans, and eggs. It is also available as an oral supplement or topical ointment.

Some research suggests that lysine may be helpful for treating certain conditions, such as cold sores and anxiety. Before taking lysine, talk to your doctor about dosage and use.

Frequently Asked Questions

  • How does lysine affect people with diabetes?

    Some studies have shown that lysine has a small impact on glucose levels. In one study, when lysine was ingested with glucose, there was a 44% decrease in the 2.5 hour glucose area response, which is used to measure how the body digests and breaks down glucose.

  • What foods naturally contain lysine?

    Lysine is consumed naturally in meat (beef, pork, poultry), cheese, certain fish, eggs, beans, legumes, and dairy products.

  • What happens to your body if you are lysine deficient?

    Most people get enough lysine in their diets, but those who do not may experience fatigue, nausea, dizziness, loss of appetite, agitation, bloodshot eyes, anemia, and reproductive challenges.

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10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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