L-arginine: Potential benefits, side effects, and risks

Taking L-arginine as a supplement can benefit the heart and muscles, but it may cause side effects such as nausea, diarrhea, and bloating.

L-arginine is one of many amino acids the body needs to function properly. Like other amino acids, L-arginine plays a role in building protein. The body uses protein to help build muscle and rebuild tissue. It converts this amino acid into the chemical nitric oxide, which helps the blood vessels open.

Researchers have investigated the effectiveness of L-arginine in treating high blood pressure and chest pain as well as in improving breathing in patients with COVID-19 requiring hospitalization.

Keep reading to learn more about the potential therapeutic benefits of L-arginine and the research behind them.

What is L-arginine?

Person's hand holding L-arginine vitamin supplements beside a bowl of food.

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L-arginine is an amino acid that helps the body build protein.

It also releases nitric oxide into the blood. Nitric oxide acts to widen blood vessels in the bloodstream, which may help certain circulatory conditions, according to a 2016 review.

The substance also stimulates the release of insulin into the body.

A person’s body naturally produces L-arginine under typical circumstances. People also get additional L-arginine as part of their regular diet.

Food sources, such as red meat, fish, dairy, and eggs, contain low amounts of L-arginine that can help the body replenish its necessary resources. Plant-based sources can include pumpkin seeds, soybeans, lentils, and chickpeas.

Occasionally, a person’s need for L-arginine may exceed their body’s ability to produce or consume it naturally. This is often true for older adults or people with certain medical conditions.

In these cases, doctors may prescribe them artificial L-arginine in the form of oral medications, injections, or creams. Several potential health conditions may benefit from an increased intake of L-arginine.

Some people take L-arginine as a supplement. However, as with any supplement, a person should use it with caution.

Although healthcare professionals consider L-arginine safe in moderate doses, too much can cause severe side effects, including death. It is also important to understand how the supplement may interact with the body and additional medications before taking it.

Side effects of L-arginine

L-arginine has some potential side effects to consider when taking it as a supplement. Some of the more common and benign side effects can include:

  • nausea
  • diarrhea
  • bloating
  • abdominal pain

However, L-arginine may result in some serious complications.

Risks and complications

L-arginine can have some potentially serious risks for certain groups of people.

These can include:

  • reduced blood pressure
  • increased risk of death after a heart attack
  • interactions with certain medications, including sildenafil (Viagra) and blood pressure medications
  • potential kidney damage with long-term supplementation
  • potential to stimulate tumor growth

Although there are risks that correlate with L-arginine use, most research indicates it is safe for most people in small doses. However, the FDA does not monitor the safety or effectiveness of supplements, so it is important to choose a reputable brand that undertakes third-party testing.

Supplements are available to purchase online, but as with any supplement or medication, the risks may outweigh the potential benefits. Therefore, a person should consult a doctor or dietitian before taking L-arginine.

Safe daily intake

The amount of L-arginine a person should take can depend on their age, existing health conditions, and the reason for supplementation.

A 2018 study of 142 participants determined that a dosage of up to 30 grams (g) per day of L-arginine is safe in most adults. Participants in the study tolerated 15–30 g of the supplement without adverse effects.

Drug interactions

Some medications and supplements may interact with L-arginine. People who take other medications or have health conditions should consult a doctor before taking it in supplement form.

Natural ways to get enough L-arginine

A major benefit of obtaining L-arginine through diet is that it is difficult to get too much. Therefore, a person can generally avoid some of the side effects of consuming excessive amounts of L-arginine.

On the other hand, food consumption alone may not provide enough L-arginine to meet a person’s needs. Therefore, individuals should discuss their options with a doctor before changing their diet.

The most suitable natural sources for L-arginine include foods high in protein. For some people, animal proteins, such as red meat, chicken and turkey breast, pork loin, and dairy products, may serve as their primary source of L-arginine.

For people who do not eat meat, plant-based proteins that contain L-arginine include lentils, chickpeas, peanuts, pumpkin seeds, and soybeans.

Individuals who find they have insufficient L-arginine to meet their needs may wish to modify their diet to include foods rich in protein.

A dietitian or doctor may be able to make meal plan suggestions to boost a person’s natural intake of L-arginine before they need to take supplements.


L-arginine is an amino acid that the body needs to function properly. A person can obtain it through the diet by consuming animal proteins and some plant-based proteins. Individuals can also take L-arginine as a supplement.

Taking L-arginine supplements can support heart health, reduce blood pressure, lower blood sugar, and support athletic performance, among other benefits.

However, side effects of these supplements can include gastrointestinal issues and interactions with medications. Therefore, it is best to talk with a doctor before taking them.