What Is Lysine?

Lysine capsules, tablets, beans, eggs, and nuts

Verywell / Anastasia Tretiak

Lysine is one of nine essential amino acids. Like the other essential amino acids, your body cannot make lysine on its own, so you must get enough from your diet.

There are two chemical versions of lysine: L-lysine and D-lysine. L-lysine is the bioactive form found in foods and supplements and used by your body. This article will focus on L-lysine.

Your body uses lysine for many vital functions, including carnitine production, collagen formation, and protein synthesis. This article will discuss the potential uses of lysine as well as supplement dosage and side effects, food sources of lysine, what to look for when choosing a lysine supplement, and other important tips.

Dietary supplements are not regulated in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement that has been tested by a trusted third party, such as USP, ConsumerLabs, or NSF. However, even if supplements are third-party tested, that doesn’t mean that they are necessarily safe for all or effective in general. It is important to talk to your healthcare provider about any supplements you plan to take and to check in about any potential interactions with other supplements or medications.

Supplement Facts

●     Active Ingredient(s): Lysine

●     Alternate Name(s): L-lysine, L-lysine hydrochloride

●     Legal Status: Legal, over the counter (OTC)

●     Suggested Dose: Dosage varies, but is generally considered safe at 6 grams (g) or less per day

●     Safety Considerations: Upset stomach, diarrhea, nausea, kidney failure, impaired calcium absorption

Uses of Lysine

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or doctor. No supplement is intended to treat, cure, or prevent disease.

Because lysine is an amino acid, your body uses it for important roles like making proteins and repairing muscles. But lysine supplements have been researched for other uses, including:

Still, the research on many of these uses is limited, and there is not much evidence to support its uses for most of these conditions. It would be best to talk with a healthcare provider before starting lysine supplements to ensure they are safe for you.

Below is a look at some key findings from studies done on lysine.

Cold Sores

Cold sores are an unpleasant side effect of HSV 1.

A 2017 review found that oral lysine supplementation of 3 grams (g) per day or more appeared to improve the subjective experiences of some people with cold sores. However, the review went on to say that more research is needed to determine whether lysine is an effective treatment for this condition.

An earlier review conducted in 2015 also did not find enough evidence to back up claims that lysine can provide cold sore relief.

Mental Health

Anxiety and stress are common concerns for many people and can affect day-to-day life. Studies have looked at whether lysine can help. However, research is limited, and it should be noted that many of the studies are small and do not include many participants.

A randomized, double-blind study found that cortisol, a hormone that is increased in times of stress, was lowered in Syrian people who consumed lysine-fortified foods for three months. The same study also found that lysine fortification reduced anxiety measures in males.

According to other research, lysine may also be used as a complementary treatment for schizophrenia, a severe mental illness. However, the studies have limitations, including small numbers of people enrolled in the trials.

A small, single-blinded, randomized, cross-over pilot study reported that people taking 6 grams of daily lysine for four weeks had improved symptoms, including reduced psychosis severity. However, the researchers of this study felt that possible placebo effects should not be excluded and could have impacted the self-reported findings.

A randomized, controlled trial investigated the use of L-lysine in addition to risperidone, a drug used to treat mental conditions, in 72 people with schizophrenia over eight weeks. In addition to their risperidone treatment, people took either 6 grams of L-lysine or a placebo. The study showed that schizophrenia symptoms decreased more for people in the L-lysine group. However, the safety and efficacy of higher doses and longer-term use of L-lysine are still uncertain.

Blood Sugar Control

It has been suggested that lysine supplements could be useful for lowering blood sugar (glucose). Lysine has been found to have potential benefits for people with high blood sugar and aid in overall blood sugar control.

A very small study of thirteen healthy people found that high doses of lysine (11 grams) along with glucose resulted in small decreases in blood sugar. Researchers think that lysine supplementation may either help with insulin secretion or help remove glucose from the blood on its own. However, there is a need for more research. Follow your healthcare provider's guidance for blood sugar control.


It has been suggested that lysine supplements can help the body absorb calcium, which may be especially beneficial for osteoporosis (a disease that causes weak, brittle bones). However, many studies have been done in vitro (in a lab or test tube) or on animals. This means that we cannot definitively conclude about lysine's effects on treating osteoporosis in humans.

An older review from 1992 reported interesting findings from human trials. The review noted two small human trials that had similar results. It was concluded that lysine supplementation helped people absorb more calcium, a mineral vital to bone health. However, no recent trials examine lysine's effects in humans with osteoporosis.

One study on rats concluded that dietary lysine increased the amount of calcium absorbed by the body. The study also reported that lysine supplementation prevented the rats from experiencing loss of bone matter, as seen in osteoporosis. It's important to note that this study was conducted in rats and did not involve human participants. We cannot say that these effects will even happen in humans.

More high-quality studies using lysine would need to be done with humans before we could make further conclusions about the effectiveness of lysine for osteoporosis. If you have osteoporosis, you should follow your prescribed treatment plan under the guidance of a healthcare provider. Consult your healthcare provider before taking any supplements.

What are the Side Effects of Lysine?

While lysine supplements are generally considered safe for most people, side effects are possible. These side effects may be common or severe.

Common Side Effects

There are a few common side effects associated with taking oral lysine supplements. A systemic review on the safety of lysine supplements noted that these side effects were most common when lysine was taken in larger doses.

Common side effects of lysine supplements include:

Typically, these gastrointestinal side effects are short-lived and can be treated at home. However, if you experience long-term side effects of taking oral lysine, a visit to your healthcare provider may be needed.

Severe Side Effects

Although rare, severe side effects are also possible when taking lysine supplements.

Kidney failure has been reported from taking too much lysine. One case report on a 44-year-old woman found that high doses of lysine caused Fanconi Syndrome, a severe disorder involving the kidneys. Her symptoms eventually led to kidney failure.

As this case report was done on just one person, the evidence of kidney failure associated with taking lysine is limited. Additional research available on this topic has mostly been performed on animal models.

Eggs, nuts, and beans
Verywell / Anastasia Tretiak


Certain people should avoid taking lysine supplements. It's important to talk to your healthcare provider first before starting any new supplements.

If you are pregnant or breastfeeding, you may not want to take lysine supplements. There is not enough evidence to know if lysine is safe for these populations. Consult your healthcare provider if you have any questions.

You should also talk to your healthcare provider if you wish to take lysine supplements but are also taking calcium supplements or have lysinuric protein intolerance, a rare condition in which the body cannot properly digest lysine and other amino acids. Lysine may increase the amount of calcium your body absorbs, which could potentially lead to hypercalcemia.

Dosage: How Much Lysine Should I Take?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage is appropriate for your individual needs.

There is no standard recommended dose for lysine supplements. Fortunately, most people can get enough lysine through their diet.

Many different lysine doses have been used in research. For example, various studies on lysine for cold sores have used a wide range of doses from 300 milligrams per day to 3 grams per day. Other studies performed on lysine supplements have used even higher amounts.

Because there is no standardized dose for lysine, it would be best to talk with your healthcare provider before starting lysine supplements. They may be able to determine the best dosage for you and answer any lingering questions.

What Happens if I Take Too Much Lysine?

Lysine is considered a safe supplement to take. There is no upper limit (UL), or maximum dose, for lysine. This is because the side effects of taking larger amounts than recommended of lysine are not thought to be severe.

Lysine is also not considered to be toxic.

Although there is no UL for lysine, some researchers have suggested one be set at 6 grams per day. This number is based on reports of no adverse effect levels from various studies that have been performed on lysine.

Experiencing any of the common side effects after taking oral lysine may mean you have taken too much. Follow your healthcare provider's advice on how much lysine you should take.


The list of possible food, drug, or supplement interactions with lysine is a short one.

Arginine, another amino acid, may interact with lysine. Taking a large dose of arginine along with lysine may cause lower levels of lysine absorption. This is because some receptors in your body prefer arginine over lysine.

Lysine and calcium are also thought to interact. Lysine has been found to increase the amount of calcium absorbed in the digestive tract.

It is essential to carefully read the ingredient list and nutrition facts panel of a supplement to know which ingredients and how much of each ingredient is included. Please review the lysine supplement label with your healthcare provider to discuss any potential interactions with foods, other supplements, and medications.

How to Store Lysine

Lysine supplements should be stored in a cool, dry place that does not receive direct sunlight. Be sure to avoid storing your supplements in an area that could become overly hot or cold.

You should discard lysine supplements after one year or as indicated on the packaging.

Similar Supplements

There are other supplements on the market that have been studied for the same uses as lysine, including:

Although there are no known interactions between lysine and these similar supplements, it would be best to discuss all supplements you plan to take with your healthcare provider.

Frequently Asked Questions

  • Is lysine safe to take when pregnant?

    Lysine may be safe to take while pregnant, but researchers and healthcare professionals do not know for sure. For this reason, it would be best to avoid taking lysine supplements during pregnancy and while breastfeeding.

    People who are pregnant or breastfeeding should be able to get enough lysine from a healthy diet.

  • Can your body make lysine?

    Lysine is an essential amino acid and cannot be made by the body. Because of this, you must get all the lysine you need through food and supplements.

    There are nine essential amino acids: lysine, leucine, isoleucine, histidine, methionine, threonine, phenylalanine, tryptophan, and valine.

  • What does lysine do for you body?

    Besides potentially treating health conditions like cold sores, high blood sugar, and osteoporosis, lysine has other roles in the body.

    Your body uses lysine to make carnitine, which is needed to make energy. Lysine also helps your body make enough collagen, an important protein found in your skin.

Sources of Lysine & What to Look For

Most people can get all the lysine they need through their diet since the amino acid is found in various protein foods.

Since lysine is so widely available in food, taking a food-first approach to getting enough of it is recommended. Lysine supplements would only be required if recommended by a healthcare professional due to an underlying health issue.

Some people, such as those who follow a vegan diet, may have difficulty getting enough lysine. However, there are lysine foods that would fit into a vegan diet.

If you are looking for lysine supplements, the National Institutes of Health (NIH) recommends checking the supplement facts label before buying any dietary or herbal supplements. The label provides important information about the number of active ingredients per serving. It should also include information about other ingredients in the supplement.

The NIH also recommends looking for a product that has been quality tested by an independent organization. Supplements that have been quality tested will include the logo of the testing agency on the label.

Examples of quality testing agencies include US Pharmacopeia (USP), the National Science Foundation (NSF), and ConsumerLab.com.

Food Sources of Lysine

The best sources of lysine come from animal foods, but it can also be found in some plant-based proteins.

The best way to make sure you are getting enough lysine in your diet is by eating a variety of protein foods, including both animal and plant sources. The recommended daily intake for lysine is 35 milligrams per kilogram (kg) of body weight.

Non-vegan food sources of lysine include:

  • Meat
  • Chicken
  • Dairy products
  • Eggs
  • Fish

Vegan food sources of lysine include:

Lysine Supplements

Lysine supplements are available in various forms, including capsules, chewable, and powders. The right form of supplement for you will depend on personal preferences.

Many lysine supplements are also vegan and/or gluten-free. The label should tell you whether the supplement is either vegan or gluten-free. The label should also list the supplement form.

Topical lysine (cream) is also available, but only in combination form. This means that lysine creams will include other ingredients, like other various vitamins, minerals, or nutrients.


Lysine is found in many protein food sources. If you choose to use lysine supplements, be sure to read the label first. Look for supplements that have been quality tested by a third party.


Lysine is an essential amino acid that can be found in high-protein foods like meat, nuts, beans, and eggs. It is also available as an oral supplement for those who need it. However, taking a food-first approach to getting enough of it is usually recommended.

Some research suggests that lysine may be helpful for treating certain conditions, like cold sores and anxiety. However, more research is needed to determine the full extent of lysine's safety and efficacy when used for these conditions. Before taking lysine, talk to your healthcare provider about dosage and how to best use the supplement.

Originally written by
Cathy Wong
Cathy Wong

Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.

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