What Supplements Increase Nitric Oxide Levels? (Not Nitric Acid)

January 13, 2026 •

4 min read

Nitric oxide (NO) is a crucial molecule produced naturally by the body, playing a vital role in blood vessel dilation, immune function, and nerve signaling. It is often confused with nitric acid, a corrosive chemical, but the distinction is critical for health. This article explores scientifically-backed supplements that increase nitric oxide levels to support vascular health and enhance athletic performance.

Quick Summary

This guide covers the most effective supplements for boosting nitric oxide, including L-arginine, L-citrulline, and beetroot. It details their mechanisms, benefits for blood flow and exercise performance, potential side effects, and important safety considerations.

Key Points

Correction: Supplements increase nitric oxide levels, not the corrosive nitric acid.
L-Citrulline is Key: L-citrulline is often more effective than L-arginine at boosting nitric oxide because it avoids the 'arginine paradox' and is converted efficiently in the body.
Beetroot's Role: High in dietary nitrates, beetroot is a natural and effective way to raise nitric oxide levels for cardiovascular and performance benefits.
Check for Third-Party Testing: The FDA does not regulate supplements, so choosing products certified by third parties like NSF or USP is crucial for safety and quality.
Food First: Incorporating nitrate-rich vegetables and foods with L-arginine and antioxidants is a safe, natural way to support nitric oxide production.
Consult a Professional: Always talk to a doctor before starting nitric oxide supplements, especially if you have existing health issues or are on medication.

Nitric Oxide vs. Nitric Acid: Clearing the Confusion

First and foremost, it is essential to correct a common and potentially dangerous misunderstanding. While many people search for information on "nitric acid" supplements, the molecule that plays a beneficial role in the human body is actually nitric oxide (NO). Nitric acid (HNO3) is a highly corrosive substance used in industrial settings, and it is not a supplement. This article focuses exclusively on supplements that increase the body's natural production of nitric oxide, a compound that helps relax blood vessels, leading to improved circulation.

The Science Behind Supplements That Boost Nitric Oxide

Nitric oxide production primarily relies on two pathways within the body. The first is the L-arginine/NOS pathway, where the enzyme nitric oxide synthase (NOS) converts the amino acid L-arginine into nitric oxide. The second, or NOS-independent pathway, involves the reduction of dietary nitrates (found in vegetables) to nitrites, and then to nitric oxide. Supplements can leverage both of these pathways to increase nitric oxide availability.

L-Arginine

L-arginine is an amino acid that acts as a direct precursor to nitric oxide. It is found in many protein-rich foods, but supplemental L-arginine is used to boost levels. However, it is affected by the "L-arginine paradox," where high oral doses can be less effective than expected because a significant portion is metabolized before reaching the bloodstream. The enzyme arginase competes with NOS for L-arginine, limiting NO production, especially in individuals with compromised vascular function.

L-Citrulline

Often considered a more effective alternative to L-arginine, L-citrulline is an amino acid that gets converted into L-arginine in the kidneys. It bypasses the arginase enzyme that breaks down L-arginine in the liver, leading to higher and more stable plasma L-arginine concentrations. This, in turn, boosts nitric oxide production more efficiently.

Beetroot (Dietary Nitrates)

Beetroot is one of the richest natural sources of dietary nitrates. Once ingested, nitrates are converted to nitrites by bacteria in the mouth and then to nitric oxide in the acidic environment of the stomach. This process is independent of the L-arginine pathway, making it an excellent way to increase NO levels, especially for those seeking a more natural option. Studies have shown that beetroot supplementation can improve exercise performance and lower blood pressure.

Glycine Propionyl-L-Carnitine (GPLC)

GPLC is a newer supplement marketed as a nitric oxide booster. Some research suggests it can increase plasma nitrate and nitrite levels, acting as a surrogate marker for NO. The mechanism is thought to involve both antioxidant effects and stimulating eNOS gene expression.

Comparison of Popular Nitric Oxide Boosters


Supplement	Primary Mechanism	Benefits	Potential Downsides
L-Arginine	Direct NO precursor via NOS pathway.	Supports blood flow, exercise performance, heart health.	'Arginine paradox' limits effectiveness; can cause GI distress at high doses.
L-Citrulline	Indirectly increases L-arginine levels.	Enhanced blood flow, increased exercise capacity, reduced fatigue, less GI issues than L-arginine.	May not be as effective in trained athletes; research is mixed.
Beetroot	Dietary nitrates convert to NO.	Enhanced endurance, lowered blood pressure, improved circulation.	Taste can be an issue for some; some supplements lack high nitrate content.
GPLC	Antioxidant effects, potential eNOS stimulation.	Supports NO metabolism, increased plasma nitrates/nitrites.	Newer research, fewer studies, potentially less established efficacy.

The Many Benefits of Boosting Nitric Oxide Levels

An increase in nitric oxide can lead to several health benefits, particularly for cardiovascular function and athletic performance.

Cardiovascular Health: By promoting vasodilation, NO helps lower blood pressure, improve blood flow, and reduce arterial stiffness.
Exercise and Recovery: Enhanced NO levels lead to better oxygen and nutrient delivery to muscles, which can increase exercise tolerance and endurance, and aid in post-workout recovery. The effects may be more pronounced in moderately trained individuals.
Erectile Dysfunction (ED): The vasodilation effects of NO are foundational to achieving an erection. Supplements like L-arginine and L-citrulline have been studied for their ability to improve blood flow and assist with mild to moderate ED.

Potential Side Effects and Safety Considerations

While generally considered safe, especially at moderate doses, NO supplements can cause mild to moderate side effects. These can include gastrointestinal issues such as stomach pain, bloating, nausea, and diarrhea. It is always recommended to consult with a healthcare professional before starting any new supplement, particularly for those with certain health conditions or taking other medications.

Special Precautions:

Interactions: NO supplements may interact with medications for high blood pressure, diabetes, and ED.
Medical Conditions: Individuals with low blood pressure, liver cirrhosis, or the genetic condition guanidinoacetate methyltransferase deficiency should avoid these supplements.
Dosage: Starting with a low dose and gradually increasing can help minimize side effects.

Foods to Naturally Increase Nitric Oxide

For those who prefer a dietary approach, many foods can naturally support NO production without the risks associated with supplements. These include:

Nitrate-Rich Vegetables: Leafy greens like spinach, kale, and arugula, along with beets, are excellent sources of nitrates.
L-Arginine Sources: Red meat, poultry, seafood, and nuts are good sources of L-arginine.
L-Citrulline Source: Watermelon is a notable source of L-citrulline.
Antioxidants: Foods high in antioxidants, like citrus fruits, berries, and dark chocolate, protect NO from degrading quickly.

Conclusion: Making an Informed Choice

Choosing the right supplement to increase nitric oxide levels depends on individual health goals and tolerance. L-citrulline and beetroot are often cited as more efficient options for increasing NO levels than L-arginine due to different metabolic pathways. However, obtaining nitrates and amino acids from natural food sources remains the safest and most reliable method for most people. Anyone considering NO supplementation should first discuss it with a healthcare provider, especially if they have existing health conditions or are taking medication. For further reading, consult reputable medical sources like the National Institutes of Health(https://pmc.ncbi.nlm.nih.gov/articles/PMC9710401/).

Frequently Asked Questions

Nitric oxide (NO) is a gas produced naturally in the body that helps with blood flow and other functions. Nitric acid (HNO3) is a toxic and corrosive chemical that is not used as a supplement.

For most healthy individuals, NO supplements like L-arginine and L-citrulline are considered safe at recommended doses, but they can cause mild side effects like gastrointestinal issues. Always consult a healthcare provider before starting a supplement, especially with existing medical conditions.

L-citrulline is generally considered more effective than L-arginine for increasing nitric oxide. It is converted to L-arginine in the kidneys, bypassing the liver's metabolism and leading to higher, more sustained NO levels.

Some effects, like vasodilation, can occur acutely within a few hours of consumption, such as with beetroot juice. More profound and sustained benefits, like improved athletic performance, may take several weeks or months of consistent use to develop.

Yes, many people can maintain healthy nitric oxide levels through a diet rich in nitrate-heavy vegetables like beets, spinach, and arugula, as well as foods containing L-arginine and antioxidants.

Individuals with low blood pressure, liver conditions like cirrhosis, or certain genetic disorders should avoid these supplements. They can also interact with certain medications, including those for blood pressure and ED.

Research is mixed, but some studies suggest that the benefits of NO supplements are more pronounced in untrained or moderately trained individuals. Well-trained athletes may have optimized NO pathways already, limiting the ergogenic effect of additional supplements.

Yes, some formulations combine both L-citrulline and L-arginine. L-citrulline is known to increase plasma arginine more effectively than supplementing with arginine alone, and some evidence suggests a combination may provide a more sustained boost in NO.