Lysine: what is it, benefits, sources, side effects

last updated: Dec 17, 2021

5 min read

If you’ve ever walked down the supplement aisle, you know there seems to be an endless amount of supplements you could take. All those choices make it difficult to know which ones you should take and what each one does. 

Lysine is one of the essential amino acids with numerous health claims and different supplement options. This article covers what lysine is, what it does, its benefits, side effects, and how you can get it.

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What is lysine?

Lysine is an amino acid the body needs for many different functions and processes. It’s one of the essential amino acids, which means the body can’t create it and it has to be consumed from nutrients in the diet. The other essential amino acids include histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, and valine. 

The body uses amino acids to make proteins, begin reactions, and create other substances the body needs. Often, amino acids are referred to as the building blocks of protein (Meenu Singh, 2011).

L-lysine is the most common form of lysine found in supplements and foods. This form is the preferred type for making protein. 

What does lysine do?

Lysine is used for many different purposes in the body, including (Meenu Singh, 2011):

  • Used to create proteins

  • Promotes cell and muscle growth

  • Used to create carnitine

  • Assists in transporting fat and lipids between cells

  • Promotes collagen growth

  • Used in creating enzymes, antibodies, and hormones

  • Aids calcium absorption

Lysine benefits

With the many different functions of lysine, it should come as no surprise this essential amino acid has numerous health benefits. Consuming adequate amounts of lysine through your diet or dietary supplements may provide potential health benefits like:

May prevent and treat cold sores

Cold sores, also called fever blisters, are caused by the herpes simplex virus type 1 (HSV-1). Once you’re exposed to the HSV-1 virus, it always remains in the body, but it usually stays dormant and doesn’t cause any symptoms. 

Sometimes, the virus will become triggered and cause cold sores to develop. Typically, a cold sore will clear up within 7–10 days without treatment. Still, the sores can be uncomfortable and annoying, so it helps to find treatments that help them clear more quickly. 

Taking a lysine supplement may help to shorten the duration, reduce the severity, and even prevent cold sore outbreaks. It’s believed that lysine may help stop HSV-1 from reproducing so that it becomes inactive again (Thein, 1984). 

One study found that taking 1,000 milligrams (mg) of lysine daily and keeping blood levels of lysine above 165 nmol/milliliter significantly decreased the number of cold sore symptoms (Thein, 1984). Another study found an ointment with lysine, zinc, and other herbs fully resolved symptoms for 40% of participants after 3 days of treatment and 87% after 6 days (Singh, 2005). 

However, not all research supports the effectiveness of lysine supplements for cold sores. A 2017 study found doses of 1,000 mg per day weren’t effective for treating cold sores. But they did find that doses over 3,000 mg per day may improve people’s experience of symptoms (Mailoo, 2017). 

May reduce blood pressure

Early research suggests lysine supplements may help lower blood pressure. Another 2017 study tested the effects of lysine supplements on adults with hypertension (high blood pressure). The results showed that the supplements helped lower pressure for people not consuming enough lysine through their diet (Vuvor, 2017). More research is needed to determine whether this benefit could be seen for people already consuming an adequate amount of lysine in their diet. 

May help manage diabetes

Diabetes is a medical condition where the amount of sugar (glucose) in the bloodstream is too high. Uncontrolled diabetes may cause health complications like increased infections, wounds that don’t heal well, vision problems, kidney disease, and changes to nerve and blood vessel health.

A small 2017 study found that taking lysine helped slow down the increase in blood sugar after eating (Ullrich, 2017). If this effect is confirmed in larger studies, it could help keep blood sugar levels more stable throughout the day. Another study suggests lysine supplement may help manage some complications of diabetes by lowering the risk for infection (Mirmiranpour, 2016). 

May support healthy muscles

Because lysine plays a role in cell turnover and growth, researchers believe it may support healthy muscle mass and strength. One study found that over 8 weeks, a high lysine diet had a small positive effect on increasing the participants’ muscle strength (Unni, 2012). 

Another study found that adequate lysine, calcium, and vitamin D levels are essential for muscle mass, bone health, and lower body fat mass for young adult women (Aggarwal, 2020).  

May reduce anxiety

Adequate lysine intake may also be beneficial for reducing stress and anxiety levels. 

A 2004 study found that fortifying lysine-deficient people’s diets with lysine reversed their deficiency and helped significantly reduce anxiety and lower stress (Smriga, 2004). 

Another study tested the combined effects of L-arginine and L-lysine supplements. They found the supplements helped lower cortisol levels, mental stress, and anxiety (Smriga, 2007). 

May promote healthy bones

As people get older, their risk for bone fractures and osteoporosis increases. Calcium deficiencies lead to bone loss, so adequate calcium intake has long been promoted as an essential step for preventing and slowing age related bone loss and osteoporosis. 

Research suggests that lysine plays a role in calcium absorption and may help support healthy bones (Civitelli, 1992). Other studies suggest lysine promotes bone growth and collagen production, which may help support bone strength and density (Jennings, 2016).

Symptoms of a lysine deficiency

Without enough lysine in your diet, you could develop a lysine deficiency. Without enough lysine, the body will have problems creating proteins and completing other essential functions for your health. 

Here are some of the signs and symptoms of a lysine deficiency (Civitelli, 1992; Lekkarinen, 2003; Vuvor, 2017; Yin, 2017):

  • Fatigue

  • Poor concentration

  • Irritability

  • Slowed growth

  • Red eyes

  • Nausea

  • Anemia

  • Reproductive issues

  • High blood pressure

Foods high in lysine

The following are some high lysine foods (USDA, 2019):

  • Red meats (beef and pork)

  • Poultry

  • Dairy products, like yogurt and cheese

  • Cod

  • Sardines

  • Eggs

  • Soybeans

  • Quinoa

  • Lentils

  • Beans and legumes

  • Tuna

  • Tempeh

  • Tofu

Lysine supplements

A nutrition supplement may help support adequate lysine intake if you’re unable to meet your needs through your diet alone. L-lysine is the form most commonly used in dietary supplements. 

The recommendations for how much lysine to take vary based on the studies and use. A safety assessment completed in 2019 found that most people can tolerate up to 6,000 mg per day without any adverse effects (Hayamizu, 2019). 

However, this amount is higher than most studies tested, which often tested doses ranging from 1,000 to 3,000 mg of lysine per day. 

Consult with a health care professional for medical advice before starting any dietary supplements to find out what dose may be appropriate for you. 

Lysine side effects

There are few known side effects of taking a lysine supplement. However, any dietary supplement can cause side effects like:

  • Nausea, vomiting, bloating, and upset stomach

  • Gas, diarrhea, or constipation

  • Headaches

Still, more long-term research is needed to fully understand the effects of taking a lysine supplement. We don’t know much about how lysine supplements may affect a person while pregnant or breastfeeding, so it’s generally recommended to limit supplement intake while pregnant unless approved by your healthcare provider. 


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

December 17, 2021

Written by

Ashley Braun, RD, MPH

Fact checked by

Steve Silvestro, MD

About the medical reviewer

Dr. Steve Silvestro is a board-certified pediatrician and Associate Director, Clinical Content & Education at Ro.