L-arginine is a naturally occurring amino acid that's found in food. It also plays a role in several bodily functions, such as making protein.
L-arginine also affects the release of growth hormones, insulin, and other substances in your body. Your body may also convert L-arginine to a chemical called nitric oxide, which widens blood vessels and improves blood flow. Vitamin K Rich Foods
The human-made version of L-arginine is thought to work similarly to the natural amino acid in your body.
This article discusses what you should know about L-arginine in terms of its potential uses, side effects, and interactions.
Dietary supplements are not regulated the way drugs are 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 tested by a trusted third party, such as U.S. Pharmacopeia, (USP), ConsumerLab.com, or NSF International.
However, even if supplements are third-party tested, they are not necessarily safe for all or effective in general. Therefore, talking to your healthcare provider about any supplements you plan to take and asking about potential interactions with other supplements or medications is essential.
Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.
As with many natural products, L-arginine is used for various purposes. Several studies have assessed L-arginine for the following potential uses.
L-arginine might provide some value to people with metabolic conditions (e.g., high blood sugar and excess weight) and heart disease. But it's unclear how effective L-arginine is because of the variability (important differences) between previous clinical trials.
For example, there were different L-arginine dosage forms among studies. And there were differences in the L-arginine dosages (amounts or strengths) and the length of therapy.
For these reasons, researchers conducted a systematic review and meta-analysis (analytical review of a collection of studies) to more clearly understand L-arginine's benefits.
According to research, L-arginine might improve blood flow in select groups of people. It may increase nitric oxide levels in people with metabolic conditions and heart disease. However, the results were unclear in the studies reviewed.
Further research with higher-quality clinical trials is still necessary—especially since there is a concern that L-arginine might cause more harm in people with a recent heart attack.
Postpartum hypertension is a condition of high blood pressure after giving birth. A systematic review found insufficient data to make clear conclusions about L-arginine's benefits and risks for this condition.
Further high-quality clinical trials with additional data are still needed.
According to the National Library of Medicine (NLM), L-arginine is possibly effective for erectile dysfunction (ED).
A review also suggested that people with ED might benefit from L-arginine alone or in combination with other medications. But additional research with larger and higher-quality studies is still warranted.
In a systematic review, people assigned female at birth who were experiencing fertility problems benefited from antioxidants—like L-arginine.
These antioxidants didn't seem to increase the risk of digestive system-related side effects, miscarriages, multiple births, or ectopic pregnancies.
While this looks promising, the results are from studies considered to be of low quality. For this reason, more high-quality clinical trials are necessary to better evaluate the effects and safety of L-arginine's use for fertility problems.
L-arginine is sometimes touted as a natural sleep aid, reducing wakefulness and helping you feel better rested. Research supporting this is limited. Among the studies that have been done is an animal study that shows a positive connection between nitric oxide from L-arginine and REM sleep. This may ultimately mean that L-arginine supplementation could help prevent diseases resulting from REM sleep deprivation.
As with many medications and natural products, side effects are possible with L-arginine.
In general, short-term use of L-arginine is likely safe in various dosage forms for most people, but there are potential side effects.
For example, when taken by mouth, common side effects may include:
While L-arginine is safe for most people, there's a chance of severe side effects in some people. Those with existing health conditions also need to be aware of possible problems that can occur if they take L-arginine:
If you're having a severe allergic reaction or if any of your symptoms feel life-threatening, call 911 and get medical help right away.
Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.
While there are some human studies on L-arginine, high-quality clinical trials are still necessary.
For this reason, there are no guidelines on the appropriate dosage to take L-arginine for any condition. If you take L-arginine, follow your healthcare provider's suggestions and product label instructions.
There is little information about L-arginine toxicity and overdoses in humans. But generally, L-arginine seems safe with short-term use of up to 20 grams (g) daily.
Overdoses with L-arginine, however, might be similar to its potential common or severe side effects, which might be exaggerated or excessive.
High doses of L-arginine might promote tumor growth, plus large amounts of L-arginine may also increase the levels of specific white blood cells. But longer and higher-quality clinical trials are still needed to assess L-arginine's safety in humans better.
Use caution when taking L-arginine with the following:
It is essential to carefully read a supplement's ingredients list and nutrition facts panel to learn which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.
Since storage instructions may vary by product, carefully read the directions and packaging label on the container.
Keep your medications tightly closed and out of the sight and reach of children and pets, ideally locked in a cabinet or closet. Store your medications in a cool and dry place.
Discard after one year or as indicated on the packaging. Avoid putting unused and expired drugs down the drain or in the toilet.
Visit the FDA's website to know where and how to discard all unused and expired drugs. You can also find disposal boxes in your area. Ask your pharmacist or healthcare provider if you have any questions about the best ways to dispose of your medications or supplements.
L-arginine is a naturally occurring amino acid that may be converted to a chemical called nitric oxide. And like L-arginine, nitric oxide is also available as a human-made version.
For these reasons, nitric oxide is likely the most similar natural medication to L-arginine.
There are several different sources of L-arginine.
L-arginine is a naturally occurring amino acid that's found in food.
Some foods that contain L-arginine include:
L-arginine is available in a variety of forms, including capsules and tablets. If you have difficulties swallowing pills, L-arginine might also be available in other dosage forms, such as liquid and powder.
L-arginine may also be available in inhalation, intravenous (into the vein), toothpaste, and topical formulations (e.g., cream and gel). There may also be vegan and vegetarian options.
What works for you will depend on your preference and the effects you hope to achieve. Each product may work a bit differently, depending on the form. Thus, following your healthcare provider's recommendations or label directions is essential.
L-arginine is a naturally occurring amino acid that's found in food. It may have potential uses for metabolic conditions (e.g., high blood sugar and excess weight), heart disease, postpartum hypertension (high blood pressure after childbirth), erectile dysfunction (ED), and fertility problems. In general, short-term use of L-arginine seems safe.
But as with many medications and natural products, side effects and medication interactions are still possible. High-quality, long-term clinical trials are still necessary to evaluate L-arginine's effectiveness and safety.
Before taking L-arginine, contact your registered dietitian nutritionist, pharmacist, or healthcare provider to help you safely achieve your nutrition and health goals.
Rodrigues-Krause J, Krause M, Rocha IMGD, et al. Association of L-arginine supplementation with markers of endothelial function in patients with cardiovascular or metabolic disorders: a systematic review and meta-analysis. Nutrients. 2019;11(1):15. doi: 10.3390%2Fnu11010015
Magee L, von Dadelszen P. Prevention and treatment of postpartum hypertension. Cochrane Database of Systematic Reviews. 2013;4:CD004351. doi: 10.1002/14651858.CD004351.pub3
Kolwal A, Manohar JS, Sathyanarayana Rao TS, et al.L-arginine and erectile dysfunction.Journal of Psychosexual Health.2019;1(1):37-43:doi:10.1177/2631831818822018
Showell MG, Mackenzie-Proctor R, Jordan V, et al. Antioxidants for female subfertility. Cochrane Database of Systematic Reviews. 2020;8:CD007807. doi: 10.1002/14651858.CD007807.pub4
Jiang J, Gan Z, Li Y, et al. REM sleep deprivation induces endothelial dysfunction and hypertension in middle-aged rats: Roles of the eNOS/NO/cGMP pathway and supplementation with L-arginine. PLoS One. 2017;12(8):e0182746. doi:10.1371/journal.pone.0182746
Bahadoran Z, Mirmiran P, Tahmasebinejad Z, Azizi F. Dietary L-arginine intake and the incidence of coronary heart disease: Tehran lipid and glucose study. Nutr Metab (Lond). 2016;13:23. Published 2016 Mar 15. doi:10.1186/s12986-016-0084-z
McNeal CJ, Meininger CJ, Reddy D, et al. Safety and effectiveness of arginine in adults. The Journal of Nutrition. 2016;146(12):2587S-2593S. doi: 10.3945/jn.116.234740
National Institutes of Health Office of Dietary Supplements. Dietary supplement label database.
By Ross Phan, PharmD, BCACP, BCGP, BCPS Ross is a writer for Verywell and has years of experience practicing pharmacy in various settings. She is also a board-certified clinical pharmacist, the founder of Off Script Consults, and director of the PharmacyChecker international verification program.
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