Nitric Oxide Supplements: What They Do and What the Evidence Shows

You may have read about nitric oxide in relation to cardiovascular health and function. In fact, nitric oxide supplements are among the most heavily marketed products in the sports nutrition world. But can nitric oxide supplements actually boost your nitric oxide levels?

In this article, we dig into how these supplements may work, which ingredients have the strongest evidence, where the research falls short, and which safety considerations are important to keep in mind.

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What Is Nitric Oxide? And Why Does It Matter?

Nitric oxide (NO) is a gaseous signaling molecule your body produces naturally. This is primarily done by converting the amino acid L-arginine via the nitric oxide synthase (NOS) enzyme. So, what’s all the hype about?

NO plays a role in vasodilation, meaning it signals the smooth muscle lining your blood vessel walls to relax. This widens your blood vessels and increases blood flow.

And more blood flow may mean more oxygen and nutrients reach working muscles, faster clearance of metabolic waste, and lower resistance in the vascular system. 

On top of this, NO plays roles in neurotransmission, immune function, and hormone signaling.

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How Nitric Oxide Supplements Work

You can’t actually take NO as a supplement. Instead, NO products typically contain precursors or compounds that support your body’s own NO production. These may include L-arginine, L-citrulline, dietary nitrates, or beetroot.

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The L-Arginine Pathway

L-arginine is the raw material your body uses to make NO—the NOS enzyme converts it into NO and L-citrulline. For decades, L-arginine was the go-to supplement for boosting nitric oxide. 

But as with most things, there’s a catch: Oral L-arginine is poorly and inconsistently absorbed. This is because a large portion of it is broken down in the gut and liver before it reaches general circulation (often called first-pass metabolism).

This means you would need a large oral dose of L-arginine to meaningfully raise NO. However, large doses may cause digestive symptoms, such as nausea, cramping, or diarrhea, which may make them not very practical.

With that said, there has been some research reporting that L-arginine supplementation benefits respiratory response and exercise performance. Yet, these effects tend to be more prominent in untrained or moderately trained individuals than in trained athletes.

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The L-Citrulline Advantage

Due to the downsides of taking large doses of L-arginine, L-citrulline is now widely considered the more effective oral precursor for raising plasma arginine and, in turn, NO.

L-citrulline is absorbed in the small intestine and converted back into L-arginine in the kidneys, which, thus, bypasses the first-pass breakdown problem.

Research has associated L-citrulline (particularly as citrulline malate, a combination with malic acid) with increased working capacity and reduced muscle fatigue in exercise studies. 

Typical research doses of citrulline malate range from 6 to 8 grams, usually taken about 60 minutes before exercise. However, many commercial pre-workout products contain far less than the doses used in studies. This is why it’s always important to check labels carefully and talk with a licensed healthcare provider before adding any supplement to your routine.

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Dietary Nitrates and Beetroot

Dietary nitrates are found in beetroot, leafy greens, and other vegetables; these are converted to nitrite by bacteria in your mouth, then to NO in the stomach and bloodstream under acidic conditions. 

Researchers report that multiple studies on beetroot juice have shown significant increases in plasma nitrite, a marker of NO production.

In fact, beetroot juice has the most consistent evidence for helping your body use oxygen more efficiently during easy-to-moderate exercise, which may translate into better endurance. As with the other ingredients listed above, the effects tend to be smaller and less consistent in highly trained athletes than in recreational exercisers. 

Interestingly, antibacterial mouthwash may actually disrupt the oral bacteria needed to convert nitrates. And this may be something to consider when exploring potential improvements in nitric oxide levels.

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What the Research Actually Supports

NO blood flow supplements have been linked to exercise performance, muscle endurance, blood pressure, cardiovascular health, and more. So, how much can these supplements help? Here’s what the research shows.

Exercise Performance and Muscle Endurance

L-citrulline malate has shown the most consistent results for reducing muscle soreness and fatigue during resistance exercise. Some studies even report improvements in repetition volume (the ability to perform more reps before failure). 

Meanwhile, beetroot and dietary nitrates have more evidence for endurance activities, such as cycling and running, than for strength or power output. And L-arginine shows modest effects that appear mainly in untrained individuals.

In other words, for trained athletes with already-optimized cardiovascular function, the performance benefit of nitric oxide supplements may be marginal. The research consistently notes that nitric-oxide-associated benefits are most apparent in untrained or moderately trained people.

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Blood Pressure and Cardiovascular Support

Some research supports modest reductions in resting blood pressure with consistent nitrate or L-citrulline intake. The evidence also points to potential benefits that have been studied for pregnancy-related hypertension under medical supervision, as well as broader cardiovascular health. 

With that said, these supplements are not a substitute for treating diagnosed hypertension or cardiovascular disease. If you have a cardiovascular condition or take blood-pressure medication, it’s essential to speak with a licensed provider before using NO-boosting supplements. This is especially true since some of these supplements may be unsafe for certain individuals. 

If you’re managing weight or metabolic health alongside blood pressure, caution may also be relevant due to the interconnectedness of these systems. Ultimately, a licensed healthcare provider can help determine what’s best for you.

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Recovery and Muscle Soreness

Citrulline malate has shown some evidence for reducing delayed-onset muscle soreness (DOMS) in the 24 to 48 hours after resistance training. The proposed mechanism is improved blood flow, which may help clear metabolites such as lactate and ammonia from muscle tissue. 

The evidence here, however, is not definitive; the study populations tend to be relatively small, and the study methods also vary.

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Claims That Outpace the Evidence

Marketing tends to get ahead of the data. With that in mind, here are some claims that may be too good to be true:

• “Massive pumps” and visible muscle fullness: The vasodilation is real, but the cosmetic “pump” during training is transient and doesn’t translate to lasting muscle growth.
• Cognitive and mood benefits: Some products suggest NO boosters sharpen focus or mental performance. The evidence is very limited and largely indirect, so this claim shouldn’t be taken at face value.
• Erectile function: Since erections depend on healthy blood flow, and nitric oxide helps widen blood vessels, some research has explored whether nitric oxide precursors may support erectile function in certain individuals, but the evidence remains limited and these supplements should not replace medical evaluation or treatment. For more information regarding potential options, read our overview of the Tadalafil & Vardenafil Combination: Uses, Benefits & Risks.
• Fat loss: There’s no direct evidence that NO precursors drive fat loss. Some products bundle them with stimulants and credit the combination, which is misleading.

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Safety Considerations and Who Should Be Cautious

Just because someone says a supplement helped them, it doesn’t mean it’s right for you. Here are some safety considerations to keep in mind when it comes to nitric oxide supplements.

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General Safety Profile

L-citrulline and dietary nitrates are generally well tolerated at research-supported doses. But L-arginine at high doses (above roughly 10 grams) is more likely to cause digestive side effects. 

Keep in mind that most supplements are not FDA-regulated for efficacy, which means label claims aren’t independently verified. On top of this, quality, purity, and actual dosing may vary widely between products. 

To be safe, make sure to look for third-party tested products, and always consult a provider before adding anything new to your regular health routine.

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Interactions and Contraindications

If any of the following apply to you, it’s essential to discuss your options with a provider first:

• You’re taking antihypertensive or nitrate-based heart medications (such as nitroglycerin): Combining these with NO-boosting supplements may cause dangerous drops in blood pressure.
• You’re taking PDE5 inhibitors (such as sildenafil/Viagra or tadalafil/Cialis): These medications already act on the NO-related pathways, which means adding NO precursors may amplify blood-pressure-lowering effects.
• You’ve been diagnosed with kidney disease: L-arginine and L-citrulline metabolism involves the kidneys. If you’re dealing with impaired kidney function, caution is advised.
• You’re pregnant: While research notes potential benefits for pregnancy-related hypertension, NO supplementation during pregnancy requires direct medical supervision.
• You have herpes simplex virus (HSV): High-dose L-arginine may promote HSV replication. Anyone with a history of cold sores or genital herpes should check with a provider first.

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Dosing Guidance

For dosing, here are the research-supported reference ranges. But keep in mind that individual needs vary.

• Citrulline malate: Approximately 6 to 8 grams, taken about 60 minutes before exercise.
• L-arginine: Approximately 3 to 6 grams, though bioavailability limitations make it a less preferred option.
• Beetroot juice: Approximately 500 mL (roughly 300 to 400 mg of nitrate), consumed 2 to 3 hours before exercise, based on endurance research.

At the end of the day, a licensed provider can help determine what, if anything, is appropriate for your individual situation.

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Where Nitric Oxide Support Fits in a Broader Performance Strategy

Blood flow, oxygen delivery, and metabolic efficiency are foundational to performance. But they’re shaped by far more than any single supplement. Sleep quality, training programming, nutrition, hormonal health, and structured recovery all still matter. And treating a nitric oxide booster as a standalone fix probably won’t result in what you’re after.

For adults noticing age-related declines in energy, recovery, and muscle performance, a more comprehensive look at your health may be more useful than stacking over-the-counter products. 

Medically guided programs may help evaluate the broader factors that influence performance and recovery with appropriate monitoring and follow-up. Read more about one option here: Sermorelin Reviews: User Experiences and Benefits. Another avenue to explore may be cellular energy; if you’re curious to learn more, review our explainer article, What is NAD?.

For getting started with a provider-led approach, consider filling in our quick online intake. From there, Eden connects you with a licensed healthcare provider who reviews your health history, goals, and lifestyle to determine which approach, if any, is the right fit. Not ready to take that leap? Explore how Eden connects you to metabolic health care first.