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Your body needs arginine, which is more commonly called L-arginine when in supplement form, for many critical processes.

For example, the body needs it to produce nitric oxide — a vasodilator that widens your blood vessels, allowing for increased blood flow. It is also required to produce other amino acids like proline (1).

The body also needs arginine for immune function, cellular communication, and more (2).

Most people do not need to supplement with L-arginine. It may be necessary under specific circumstances and may be helpful for certain populations.

What is L-arginine?

Amino acids are the building blocks that combine to form proteins. They have three categories:

• nonessential
• essential
• conditionally essential

The body can make nonessential amino acids naturally but must get essential amino acids through diet (3).

Some amino acids are considered conditionally essential, or semi-essential. These amino acids are considered essential only under specific circumstances such as during critical illness, adolescence, or pregnancy (3).

L-arginine is classified as a conditionally essential amino acid, meaning the body needs it in greater amounts in specific circumstances. For example, the body needs more L-arginine during infancy, pregnancy, and during critical illness (4).

In these situations, the body is unable to meet L-arginine demands on its own. As a result, it needs extra L-arginine through dietary intake or supplementation.

L-arginine supplements have also been shown to be helpful for those with certain medical conditions like high blood pressure and erectile dysfunction (ED) and may be beneficial for boosting athletic performance (5, 6, 7).

Who shouldn’t take it

Most people do not need to supplement with L-arginine. This is because the body can meet L-arginine demands through dietary consumption of protein sources like fish and nuts, body protein breakdown, and endogenous L-arginine production by the kidneys (8).

Research suggests that L-arginine supplements are generally safe for most people, even when taken in high doses for long periods. However, some people may experience side effects like stomach pain and diarrhea when taking more than 9 grams per day (1, 9).

L-arginine supplements aren’t safe for everyone.

They should be avoided by people who have (10):

• had a recent heart attack
• kidney disease or low blood pressure (hypotension)
• an inherited condition that impacts arginine metabolism, called guanidinoacetate methyltransferase deficiency

L-arginine may also interact with medications like those used to treat high blood pressure.

Check with your healthcare professional if you have questions about taking L-arginine supplements. They can help you determine whether L-arginine supplements are safe and appropriate for your needs.

A quick look at our picks for the best L-arginine supplements

• Best single ingredient L-arginine: Pure Encapsulations L-Arginine, Thorne Research Perfusia-SR, Klaire Labs L-Arginine HCl, and Life Extension L-Arginine Caps
• Best for athletes: NOW Sports L-Arginine Powder and ONIT Total Nitric Oxide
• Best for ED: Doctor’s Best L-Arginine Powder

How we chose the best L-arginine supplements

Healthline evaluated the top L-arginine supplements based on these criteria:

• Third-party testing. A third-party testing facility can ensure the quality and purity of the product.
• Transparency. The packaging discloses the amount of L-arginine the product supplies.
• Ingredient quality. The supplement contains high quality ingredients and avoids unnecessary fillers and additives.

A note on price

General price ranges with dollar signs ($ to $$$) are indicated below. One dollar sign means the product is rather affordable, whereas three dollar signs indicate a higher price.

Generally, prices range from $0.09–$1.33 per serving, or $13.97–$39.99 per container, though this may depend on where you shop.

Formulations for athletes tend to be more expensive.

Note that serving sizes vary by product but are generally 1–4 capsules.

Pricing guide

• $ = under $0.25 per serving
• $$ = $0.25–$0.75 per serving
• $$$ = over $0.75 per serving

Healthline’s picks for the best L-arginine supplements

Best single-ingredient L-arginine products

These supplements contain only L-arginine and are best for people who may need to supplement in instances where L-arginine is in higher demand by the body, such as during pregnancy, injury, or illness.

Pure Encapsulations L-Arginine

Price: $$

Pure Encapsulations is a trusted name in the supplement world and a preferred brand among many healthcare professionals.

Pure Encapsulations products exceed standards set by United States Pharmacopeia (USP), an organization that sets strict standards for the quality and purity of dietary supplements.

Additionally, Pure Encapsulations products are tested by third-party independent laboratories like Silliker, Eurofins, and Intertek.

This gluten-free, hypoallergenic supplement provides 1,400 mg of L-arginine per serving. What’s more, the only other ingredient is the softgel vegetarian capsule made with cellulose and water.

This supplement is also free from gluten, dairy, soy, tree nuts, and peanuts.

Pros

• third-party tested
• exceeds standards set by USP

Cons

• a bit pricey

Shop now at Amazon

Thorne Research Perfusia-SR

Price: $$

This sustained-release L-arginine supplement from Thorne Research breaks down slowly to provide a steady, even flow of L-arginine into your system.

It contains 1,000 mg of L-arginine per serving, as well as some fillers like cellulose and other ingredients to support its time-release effects.

The supplement is manufactured in a certified Good Manufacturing Practices (cGMP) facility that meets Food and Drug Administration (FDA) quality standards.

Also, Thorne’s products are made in laboratories that meet standards set by NSF International and Australia’s Therapeutic Goods Administration (TGA). TGA is a regulatory agency run by the Australian Government Department of Health that assesses the safety of supplements.

This supplement is dairy, soy, and gluten-free.

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Klaire Labs L-Arginine HCl

Price: $

Klaire Labs supplements are a favorite among healthcare providers because they’re made with hypoallergenic, high quality ingredients. Its products are manufactured in a cGMP facility that meets FDA guidelines.

This supplement boasts 700 mg of L-arginine per serving and contains the preservative ascorbyl palmitate and anti-caking agent silicon dioxide.

The “HCl” in the name refers to hydrochloride, meaning that this product is L-arginine bound with hydrochloric acid. The added hydrochloric acid may help your body better absorb the L-arginine (11).

Klaire Labs L-arginine-HCL is free from common allergens including milk/casein, eggs, fish, shellfish, tree nuts, peanuts, wheat, gluten, and soybeans. Additionally, it does not contain artificial colors, flavors, or preservatives.

Shop now at Amazon

Life Extension L-Arginine Caps

Price: $

This vegetarian and gluten-free L-arginine supplement provides 700 mg of L-arginine per capsule, plus 10 mg of vitamin C to support artery health. Vitamin C plays many important roles in the body, including protecting cells against oxidative damage (12).

Life Extension is GMP certified and its products are verified using testing methods including high performance liquid chromatography and mass spectrometry. These tests help ensure their products meet standards for purity and potency. Life Extension also tests raw materials using USP standards.

This is a high quality L-arginine supplement that’s affordable and can be found in many major grocery stores for people who would rather purchase supplements in person rather than online.

Shop now at Life Extension

Best for athletes

Studies show that L-arginine supplements may effectively improve athletic performance when taken in specific doses.

NOW Sports L-Arginine Powder

Price: $$

NOW Sports L-arginine powder comes in a convenient powdered form, making it an easier choice for those who don’t like to swallow pills.

Two teaspoons (6 grams) delivers a higher dose of L-arginine, which may be appropriate for people looking to improve certain aspects of athletic performance.

For example, a 2020 review suggested that, in order to improve athletic performance, L-arginine supplementation should be adjusted to .33 g/lb (0.15 g/kg) of body weight, taken between 60–90 minutes before exercise.

They also suggested that longer term arginine supplementation should include 1.5–2 grams of arginine per day for 4 to 7 weeks to improve aerobic performance, and 10–12 grams per day for 8 weeks to improve anaerobic performance (5).

NOW L-arginine powder is Informed Sport certified. This means that the product is independently tested for substances banned in sport by LGC, a globally recognized sports doping control and supplement testing lab.

NOW Informed Sport certified products are blind-sampled up to four times every year at the retail level. Consumers can find testing results at informed-sport.com.

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ONNIT Total Nitric Oxide

Price: $$$

ONNIT Total Nitric Oxide combines L-arginine with vitamin C, L-citrulline, and a blend of other ingredients, including beetroot powder. It provides 1.4 grams of L-arginine and 3 grams of L-citrulline per 11.8-gram scoop.

L-citrulline is another amino acid shown to improve certain aspects of athletic performance in some studies.

For example, a 2019 study found that supplementing with a combination of 1.2 grams of L-arginine and 1.2 grams of L-citrulline for 6 days improved cycling performance and the perception of physical exertion in college-age male athletes compared with a placebo (13).

However, study findings on L-citrulline’s impact on athletic performance have been mixed, and future well-designed studies are needed before strong conclusions can be made (14).

ONNIT Total Nitric Oxide is NSF Certified for Sport. This certification verifies that the product does not contain substances banned by major athletic organizations, that the contents match the supplement label, and that the supplement is free from contaminants. It also ensures the product is made in a facility that’s audited twice per year by NSF International (15).

Best for erectile dysfunction

Research suggests that L-arginine may improve ED symptoms when combined with drugs used to treat ED like tadalafil (Cialis).

A 2020 study that included 120 older adults with ED found that those who were treated with a combination of 5 grams of L-arginine and 5 mg of tadalafil for 6 weeks experienced the greatest improvement in Sexual Health Inventory for Men (SHIM) questionnaire scores and the highest levels of testosterone when compared with groups that received L-arginine or tadalafil alone (16).

A 2022 study that included 98 people with ED found that a daily dose of 6 grams of L-arginine for 3 months significantly improved penile erectile function in those with mild-moderate ED (17).

For people interested in taking L-arginine to improve ED symptoms, it’s important to seek advice from a trusted healthcare professional first.

Doctor’s Best L-Arginine Powder

Price: $$

Because research suggests that higher doses of L-arginine may be more effective for improving erectile dysfunction, people wishing to try L-arginine under a doctor’s supervision may want to purchase a supplement that delivers more than 5 grams of L-arginine per serving.

It’s best to seek specific dosing recommendations from a healthcare professional, especially if you’re taking any medications, including those used to treat ED.

Doctor’s Best L-Arginine Powder provides 6 grams of L-arginine per 1 scoop, making it a high dose supplement.

The product is gluten-free and vegan, and it can be mixed with a beverage of your choice, such as juice or water. This supplement is manufactured in a cGMP facility that meets FDA quality standards.

Shop now at Amazon

Comparing L-arginine supplements

ProductsPrice per servingDoseProsConsPure Encapsulations L-Arginine$$1.4 g• third-party tested
• exceeds USP standards• priceyThorne Research Perfusia-SR$$1 g• made in labs that meet NSF International and Australia’s TGA standards• priceyKlaire Labs L-Arginine HCl$700 mg• inexpensive
• free from common allergens• not third-party testedLife Extension L-Arginine Caps$700 mg• affordable
• contains vitamin C• not third party testedNOW Sports L-Arginine Powder$$6 grams• Informed Sport Certified and blind-sampled
• high dose
• affordable• not ideal if you prefer capsulesONIT Total Nitric Oxide$$$1.4 grams• NSF certified for sport
• contains other ingredients ideal for athletes• priceyDoctor’s Best L-Arginine Powder$$6 grams • higher dose more ideal for ED• not third-party tested

How to choose the best L-arginine supplement

When shopping for L-arginine supplements, seek out products that have been third-party tested to ensure quality. Although the FDA regulates dietary supplements, this is minimal compared with the agency’s oversight of prescription medications.

Bear in mind that the rigor of third-party testing varies. The best way to ensure appropriate testing is to look for a label from a certification program like USP, Informed Choice, ConsumerLab, or NSF International.

If a company’s sole assertion of third-party testing is a claim on its website that doesn’t link to a specific certification program, you may want to choose another product.

If you can’t find a product tested by a third party, look for one manufactured at a cGMP facility to ensure that it meets FDA quality standards.

Next, you should choose a product that most closely aligns with your dietary needs, whether that’d be a gluten-free, allergen-free, organic, or GMO-free product.

Because L-arginine is primarily found in animal foods, many L-arginine supplements are not vegetarian. If you’re vegan or vegetarian, look for supplements specifically labeled as suitable for these diets.

If ED is your primary concern, you should consult a healthcare professional for more treatment options.

Dosage

Keep in mind that L-arginine isn’t an essential nutrient, so no set dosage guidelines exist. Your healthcare professional may give you dosage guidance if you need it.

Dosing depends on what you’re intending to treat. For example, higher doses of L-arginine may be helpful for improving ED symptoms and athletic performance, while lower doses may be appropriate for treating other symptoms or medical conditions (5, 17).

It’s important to understand that, because L-arginine is conditionally essential and supplementation has been shown to benefit only certain populations, most people do not need to supplement with L-arginine.

If you’re interested in taking a supplement containing L-arginine to treat a specific medical condition like ED or to improve athletic performance, discuss dosing with your healthcare professional.

Even though L-arginine supplements are generally safe to take, they’re not appropriate for everyone and may interact with commonly prescribed medications.

It’s also recommended to keep dosing below 9 grams per day to avoid potential side effects, including nausea and diarrhea.

Useful supplement shopping guides

Check out these two articles to help make supplement shopping a breeze:

• How to Choose High Quality Vitamins and Supplements
• How to Read Supplement Labels Like a Pro

Frequently asked questions

What should you do if you took too much L-arginine?

Research suggests that L-arginine supplements are generally safe for most people, even when taken in high doses of up to 30 grams per day for long periods of time. Most supplements contain only around 1-5 grams of L-arginine, so it would be difficult to take too much.

Some people may experience side effects like stomach pain and diarrhea when taking more than 9 grams per day (1, 9).

Also, do not give your child L-arginine unless it’s medically necessary and was suggested by a healthcare professional. Giving a child too much L-arginine is extremely dangerous and can be fatal (10).

Is all L-arginine the same?

There are several different forms of L-arginine supplements. Talk with a trusted healthcare professional like a physician or registered dietitian to see which one is right for you.

Does L-arginine help with male enhancement?

Some research suggests that L-arginine may help improve symptoms of ED when taken in specific doses. For example, a 2022 study in 98 men with ED found that a daily dose of 6 gram of L-arginine for 3 months significantly improved penile erectile function in patients with mild-moderate ED (17).

Do not take L-arginine supplements for ED without discussing it with your doctor first. L-arginine has the potential to interact with medications, including those used to treat ED, like Viagra.

The bottom line

L-arginine is an amino acid precursor to nitric oxide, which helps boost circulation and blood flow. As such, it’s commonly used in pre-workout and male enhancement supplements.

Furthermore, pregnant women, infants, and critically injured or ill people may need more arginine than they can produce on their own.

Be sure to talk with your healthcare professional before adding supplements to your routine.