Reviewed by Vicky Davis, FNP
Written by Our Editorial Team
L-arginine is an amino acid that’s available as a dietary supplement. It’s often promoted online as a natural treatment for conditions like hypertension (high blood pressure), peripheral arterial disease (PAD) and angina.
If you’ve searched for information about natural treatments for erectile dysfunction (ED), you’ve likely seen L-arginine mentioned.
Many of the ED-related claims about L-arginine come from natural health websites, which often position L-arginine as a natural, over-the-counter alternative to prescription ED medications like sildenafil (the active ingredient in Viagra®), tadalafil (Cialis®) and others.
Currently, scientific evidence to show that L-arginine for ED is effective is very limited, with a few studies that produce different results.
However, L-arginine may potentially have other beneficial effects for your health that could make it a useful supplement for certain issues.
Below, we’ve dug into the research and explained what L-arginine is, how it works and whether or not L-arginine supplementation can work as an effective treatment for ED.
We’ve also listed other options for the treatment of erectile dysfunction, including FDA-approved medications and simple changes that you can make to your habits and lifestyle.
L-arginine is an amino acid. It’s found naturally in fish, poultry, red meat and dairy products and is used by your body to create proteins.
As an amino acid, L-arginine is quite versatile. Your body uses it for several purposes, including producing nitric oxide. L-arginine is also involved in the synthesis of other compounds, such as glutamate, creatine, proline, urea and polyamines.
Most people get their L-arginine from food. Like many other amino acids, L-arginine is also sold as a dietary supplement.
If you’ve looked at L-arginine supplements online, you might have seen claims that L-arginine is an effective natural treatment for erectile dysfunction.
Right now, studies on the effects of L-arginine as an ED supplement are mixed. However, some research suggests that using an L-arginine supplement may help to improve sexual function for men with erectile dysfunction.
Before we get into specific studies of L-arginine, it’s important to explain how erections work, as well as the role that compounds like nitric oxide play in the process.
Erections are all about blood flow. When you feel sexually aroused, your nervous system sends a signal to the tissue inside your penis, referred to as the corpora cavernosa.
The blood vessels that supply blood to your penis dilate, increasing blood flow and creating an erection.
One molecule that’s involved in this process is nitric oxide, which plays a key role in relaxing the smooth muscle tissue that controls blood flow to the erectile tissue inside your penis.
L-arginine is an important building block of nitric oxide. In fact, nitric oxide is produced within the body from L-arginine by a family of enzymes called nitric oxide synthases.
Because of L-arginine’s important role in nitric oxide production, many people believe that taking an L-arginine supplement is an easy way to boost nitric oxide levels and produce stronger, more reliable erections.
Overall, study findings are mixed but promising. In a study from 1999, researchers compared an oral L-arginine supplement with a placebo to see if L-arginine produced improvements in sexual function in men with ED.
Both the L-arginine supplement and the placebo produced improvements for a small number of the men, with the researchers concluding that there was no statistically significant difference in effectiveness between the two treatments.
On the other hand, a study published in the Journal of Sex & Marital Therapy in 2003 involving 40 men with ED from 25 to 45 found that the dipeptide arginine aspartate and Pycnogenol®, a natural health supplement made from pine bark extract, improved erections.
The supplement also produced improvements in general sexual function among the men, with more than 90 percent of the men reporting the ability to develop a normal erection following the third month of treatment.
More recently, a review published in the Journal of Psychosexual Health looked at the findings of several studies of L-arginine as a treatment for ED, noting that there is positive evidence for the efficacy of L-arginine and its combinations.
The review concluded that more research with larger sample sizes is needed to find out more about L-arginine’s potential role in treating erectile dysfunction.
Put simply, although some studies have produced promising findings, right now there just isn’t enough high-quality scientific evidence to conclusively state that L-arginine is an effective form of treatment for ED.
Does this mean that L-arginine is worthless as a supplement? Of course not. Like many other dietary supplements, the fact that L-arginine isn’t proven to treat ED doesn’t mean that it can’t potentially have other health benefits.
L-arginine supplements are often marketed as physical performance boosters that can increase blood flow and improve vascular function.
Like with many other supplements, not all of the supposed benefits of L-arginine are backed up by real scientific evidence.
However, studies have found that L-arginine may offer benefits for a diverse range of conditions, including:
Hypertension (high blood pressure). There’s some evidence that using an L-arginine supplement by mouth can reduce blood pressure, both in people with hypertension and in people with healthy blood pressure levels.
However, it is important to speak to a medical professional before taking L-arginine for blood pressure, as it shouldn’t be viewed as a replacement for existing blood pressure medications.
Peripheral artery disease. Research has found that using an L-arginine supplement or taking L-arginine by IV over a period of several weeks can increase blood flow in people with peripheral artery disease (narrowing of the arteries that supply blood to the legs).
It is important to note that long-term use of L-arginine (up to 6 months) does not appear to improve walking speed or distance in people with this condition.
Angina (chest pain). Although L-arginine doesn’t appear to widen the arteries that are involved in angina, research has found that people with angina who use L-arginine may have less severe symptoms and improved quality of life.
L-arginine also stimulates the release of several important chemical compounds within the body, including growth hormone and insulin.
Beyond helping with specific medical conditions, L-arginine’s effects on blood flow may help to improve some aspects of physical performance.
For example, a study published in the European Journal of Clinical Nutrition found that athletes who used an L-arginine supplement for 45 days showed a significant increase in VO2 max — a measure of oxygen utilization that’s closely linked to athletic performance.
However, it’s important to note that other studies of L-arginine largely don’t show the same level of improvement in athletic performance or recovery.
If you spend more than an hour or two searching for information about L-arginine supplements and sexual health in men, you’ll likely come across a claim or two that L-arginine can increase penis size, give you bigger erections or increase your level of sexual desire.
Although L-arginine’s effects on blood flow might help you to get and maintain an erection, it’s not clear that supplements containing L-arginine offer any benefits for penis size, sex drive or sexual performance in general.
In fact, there currently aren’t any supplements or medications that can reliably increase penis size.
As we’ve discussed more in our guide to penis enlargement pills, most herbal products that are promoted as being able to increase your penis size aren’t backed up by any science, and some have been found to contain hidden, potentially harmful ingredients.
Currently, the only reliable way to increase your penis size is through surgery, and this comes with some serious downsides, from temporary pain and discomfort to a risk of real changes in the function of your penis.
The good news is that you probably don’t need to worry about your penis size, at least not as much as you think. Our guide to average penis size explains why most guys are fine when it comes to measurements below the belt, at least when it comes to partner satisfaction.
Although research on L-arginine and erectile dysfunction is mixed, some studies suggest that it may offer benefits for sexual health and performance.
You can purchase L-arginine supplements online, from your local drug store and from almost all health food stores.
As L-arginine isn’t an FDA-approved medication for ED, clinical trials have not been carried out to work out the most effective dosage for improving blood flow to the penis.
Because of this, there’s no suggested dosage of L-arginine for ED or other men’s sexual health issues.
However, research into L-arginine’s effects on erectile health and sexual performance generally involves a dosage of 2.5 to 5 grams of L-arginine, taken orally.
How long does it take for L-arginine to work? Most studies of L-arginine take place over several months, meaning it’s important to be patient while using L-arginine supplements and not expect any overnight changes in your blood flow and sexual function.
If you’re considering using L-arginine, make sure to follow the usage instructions provided with your supplement. Do not exceed the recommended dosage listed on the supplement label.
Like other dietary supplements, L-arginine can potentially cause side effects. Known side effects of L-arginine include:
Low blood pressure
Pain in the abdominals
L-arginine supplements may interact with certain over-the-counter and prescription medications, including medications used to treat diabetes and cardiovascular disease.
Medications that may interact with L-arginine include isoproterenol, diabetes medications, ACE inhibitors, angiotensin receptor blockers (ARBs), antihypertensive medications, antiplatelet and anticoagulant medications, nitrates, testosterone and potassium-sparing diuretics.
L-arginine may also interact with medications for erectile dysfunction, such as sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra®) and avanafil (Stendra®).
Make sure to inform your healthcare provider about any medications you currently take or have recently used before taking L-arginine.
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While the research on L-arginine as a treatment for ED is mixed, several proven, science-based treatments for ED are available.
Currently, the most effective treatments for ED are PDE5 inhibitors. These medications work by relaxing the arteries that supply blood to your penis. This increases blood flow and can improve your erectile function and sexual performance.
PDE5 inhibitors used to treat ED include:
Sildenafil. The active ingredient in Viagra, sildenafil provides relief from ED for around four hours per dose.
Tadalafil. The active ingredient in Cialis, tadalafil is a longer-lasting medication that can provide relief from ED for up to 36 hours per dose.
Vardenafil. The active ingredient in Levitra, vardenafil provides relief from ED for four to five hours per dose.
Avanafil. Sold as Stendra, avanafil is a new, fast-acting ED medication that can work in as little as 15 minutes.
We offer several FDA-approved ED medications online, following a consultation with a licensed healthcare provider who will determine if a prescription is appropriate.
In addition to taking medication, making simple changes to your habits and lifestyle may help to improve your erections and prevent many common forms of sexual dysfunction.
For better erections and sexual activity, try to eat a healthy, balanced diet that’s rich in essential nutrients.
It’s also important to keep yourself physically active and avoid any habits that could reduce your cardiovascular well-being, such as smoking.
Our guide to natural methods for maintaining erections goes into greater detail about simple but effective changes that you can make to your lifestyle for better sexual health.
Search online for men’s sexual health supplements and you’ll find hundreds of products, each claiming to improve your erections, sexual performance and/or penis size.
While there is some evidence that L-arginine may improve blood flow to your penis, we simply don’t have enough high-quality scientific evidence yet to conclusively state that it’s an effective treatment for erectile dysfunction.
In other words, the jury is still out on whether using L-arginine for erectile dysfunction is a good idea.
Although some studies have found that L-arginine may offer mild sexual health benefits, others have found that L-arginine isn’t any more effective than a placebo.
These medications are first-line treatments, meaning they’re the first recommended treatment in men with ED.
While these may not sound as appealing as a natural supplement, they’re backed up by several large-scale clinical trials showing that they produce real, statistically significant improvements in erections and sexual function.
If you’re one of the millions of men affected by erectile dysfunction, it may be worth looking into these ED medications to improve your sexual health and performance.
Dr. Vicky Davis is a board-certified Family Nurse Practitioner with over 20 years of experience in clinical practice, leadership and education.
Dr. Davis' expertise include direct patient care and many years working in clinical research to bring evidence-based care to patients and their families.
She is also an active member of the American Academy of Nurse Practitioners.