Does Nitric Oxide Have Any Bad Side Effects? Understanding Risks and Safety

November 24, 2025 •

4 min read

According to numerous studies, while often well-tolerated, some individuals may experience mild to moderate side effects from nitric oxide (NO) supplements, especially at higher doses or with underlying health conditions. So, does nitric oxide have any bad side effects? The answer depends on individual health, dosage, and supplement type.

Quick Summary

Nitric oxide supplements, containing precursors like L-arginine and L-citrulline, can cause mild adverse effects such as digestive issues or headaches in some individuals. More serious risks, including dangerously low blood pressure and drug interactions, are possible, especially for people with pre-existing conditions.

Key Points

Blood Pressure Drop: Nitric oxide supplements can cause low blood pressure, which is a risk for those with pre-existing hypotension.
Digestive Issues: Common side effects include bloating, diarrhea, and nausea, especially at higher doses of L-arginine or L-citrulline.
Drug Interactions: NO supplements can dangerously interact with blood pressure, diabetes, and ED medications, leading to severe health complications.
Medical Condition Risks: Supplements may worsen conditions like cirrhosis, kidney disease, or herpes. A study also showed risks for heart attack patients using L-arginine.
Natural vs. Supplement: Boosting nitric oxide through nitrate-rich foods like beets is often a safer and more reliable alternative to supplementation.
Medical Consultation is Key: Always consult a healthcare professional before taking nitric oxide supplements, especially if you have pre-existing conditions or take other medications.

Understanding Nitric Oxide Supplements

Nitric oxide (NO) is a vital signaling molecule in the body that plays a crucial role in widening blood vessels (vasodilation), which improves blood flow. Because of this, NO is essential for many physiological processes, including blood pressure regulation, immune response, and athletic performance. Supplements designed to boost nitric oxide don't contain the gas itself but rather provide precursors like L-arginine and L-citrulline, which the body converts into NO. While beneficial for many, it is critical to understand the potential downsides and answer the question: does nitric oxide have any bad side effects?

Common Mild Side Effects

For most healthy individuals, nitric oxide supplements are relatively safe, but minor side effects can still occur. The likelihood of experiencing these effects often increases with higher dosages.

Gastrointestinal Distress: The most commonly reported side effects involve the digestive system. Users may experience bloating, stomach pain, diarrhea, and nausea. This is often linked to the amino acids L-arginine and L-citrulline, with higher doses being more problematic. A simple fix may be to lower the dose or take the supplement with food.
Headaches: Some people report headaches after taking nitric oxide boosters. This is likely due to the vasodilation effect, as the increased blood flow to the brain can cause a pressure change that triggers head pain.
Dizziness and Lightheadedness: Due to the blood pressure-lowering effect of nitric oxide, some users may experience dizziness or lightheadedness, particularly when standing up quickly. This is especially a risk for individuals who already have low blood pressure.
Heart Palpitations: A minor increase in heart rate or a feeling of heart palpitations has been reported by some users.

Serious Health Risks and Considerations

While mild side effects are manageable, nitric oxide supplementation poses more significant risks for certain individuals and can lead to dangerous complications if not used correctly. The risks underscore the importance of consulting a healthcare professional before use.

Dangerously Low Blood Pressure

As a potent vasodilator, nitric oxide is meant to relax blood vessels and lower blood pressure. For individuals with already low blood pressure (hypotension), this effect can be dangerous, potentially leading to fainting or other cardiovascular complications.

Interactions with Medications

Nitric oxide supplements can interact with a range of medications, amplifying or counteracting their effects.

Blood Pressure Medications: Combining NO supplements with prescription blood pressure drugs can cause blood pressure to drop to unsafe levels.
Erectile Dysfunction (ED) Medications: Like blood pressure medication, ED drugs (such as sildenafil) also increase nitric oxide. Taking them with NO supplements can lead to a severe drop in blood pressure.
Diabetes Medications: Supplements can impact blood sugar levels, which can be dangerous when combined with medications for diabetes.
Blood Thinners: Supplements may increase the risk of bruising or bleeding when taken alongside blood-thinning medications.

Aggravation of Medical Conditions

Certain pre-existing medical conditions may be worsened by nitric oxide supplements, including:

Cirrhosis: Liver scarring can be exacerbated by NO supplements.
Kidney Disease: Individuals with compromised kidney function should use caution.
Herpes Virus: Some studies suggest L-arginine may trigger viral outbreaks.
Post-Heart Attack Recovery: An older study on L-arginine showed a higher risk of adverse outcomes in patients recovering from a heart attack, though more research is needed.

Nitric Oxide Supplements vs. Dietary Sources

For those concerned about side effects, a comparison of supplements versus natural dietary sources can help inform a safer approach to boosting NO levels.


Factor	Supplements (L-arginine / L-citrulline)	Natural Sources (Nitrate-Rich Foods)
Side Effects	Potential for mild to serious side effects, especially with high doses or pre-existing conditions.	Minimal risk of side effects; high doses primarily tied to digestive upset.
Dosage Control	Easier to control precise dosage, though quality can vary between brands.	Dosage is less concentrated and more variable, relying on food intake.
Absorption	Can be less effective due to breakdown before reaching the bloodstream (L-arginine). L-citrulline is often more effective.	Efficiently converted into nitric oxide through a natural, bacteria-assisted process.
Overall Safety	Requires careful consideration and medical consultation, especially with medications or health issues.	Considered a safer and more reliable way to boost nitric oxide for most people.

How to Mitigate Risks and Supplement Safely

For those still considering supplements, several precautions can help minimize risk:

Consult Your Doctor: Always discuss any supplement use with a healthcare provider, especially if you take other medications or have pre-existing health conditions.
Start with a Low Dose: Begin with the lowest recommended dosage to see how your body reacts before increasing gradually.
Prioritize Diet: Focus on increasing natural nitric oxide production through nitrate-rich foods like beetroot, spinach, and leafy greens.
Choose Reputable Brands: Select supplements that have been verified by third-party testing organizations to ensure quality and accurate ingredient amounts.

For further information on supplement safety and benefits, consult a qualified healthcare professional or refer to research from reputable sources, like this one on dietary supplements for improving nitric-oxide synthesis from the National Institutes of Health.

Conclusion: Does nitric oxide have any bad side effects?

The answer to the question, "Does nitric oxide have any bad side effects?" is nuanced. For most healthy people using moderate doses, the risks are low and side effects are mild, if they occur at all. However, nitric oxide supplementation is not without its dangers, particularly for individuals with low blood pressure, heart disease, liver or kidney issues, or those taking certain medications. Prioritizing natural dietary sources is often the safest and most reliable way to boost nitric oxide levels. Always seek medical advice before starting any new supplement regimen to ensure it aligns with your specific health needs and circumstances.

Frequently Asked Questions

The most common mild side effects include digestive issues such as bloating, diarrhea, stomach pain, and nausea, as well as headaches and occasional heart palpitations. These are often dose-dependent and can sometimes be mitigated by taking a lower dose or consuming the supplement with food.

Yes, nitric oxide supplements can cause a significant drop in blood pressure due to their vasodilating effects. This is a particular risk for people who already have low blood pressure (hypotension) or those taking medications for high blood pressure.

Individuals with certain health conditions, including low blood pressure, cirrhosis, heart disease (especially post-heart attack), kidney disease, and the herpes virus, should avoid or use caution with nitric oxide supplements. Anyone on blood pressure, diabetes, or erectile dysfunction medications should also avoid these supplements.

Yes, there are several potential drug interactions. NO supplements can amplify the effects of blood pressure medication and erectile dysfunction drugs, leading to dangerously low blood pressure. They may also affect blood sugar levels when combined with diabetes medication and interfere with some blood thinners.

For most people, increasing nitric oxide naturally by consuming nitrate-rich foods like beetroot juice and leafy greens is a safer and highly effective alternative to supplementation. This approach minimizes the risk of side effects associated with concentrated supplement doses.

Yes, it is highly recommended to consult a healthcare provider before starting any new supplement, including nitric oxide boosters. A doctor can help assess your individual health profile and check for potential interactions with any medications or pre-existing conditions.

High doses of L-arginine, a common precursor in nitric oxide supplements, are more likely to cause gastrointestinal issues such as stomach discomfort, diarrhea, and bloating. Studies have shown these side effects become more frequent with doses exceeding 9 grams.