The Nitric Oxide Side Effects You Need to Know Before Your Next Workout


You’re at the gym crushing arm day with your heart pumping and your blood flowing. Nitric oxide is at work in your body widening your blood vessels and delivering oxygen and nutrients to your muscles. You’re feeling the pump. Suddenly, an uncomfortable feeling of dizziness hits, or you feel compelled to head for the restroom.

All types of supplements can come with side effects, and if you’ve experienced some unpleasant symptoms during your workout, a nitric-oxide-boosting supplement may be the culprit. While nitric oxide is a natural substance in your body, too much of anything can be detrimental. 

An open bottle of supplements, with blue and while capsules spilling out.
Credit: Piyato / Shutterstock

Whether you’re a full-time bodybuilder or simply consume nitric oxide to put a bit of pep in your step during your workouts, you need to know exactly what this compound does and how it may affect you (for better or worse). 

Editor’s Note: The content on BarBend is meant to be informative in nature, but it should not be taken as medical advice. When starting a new training regimen and/or diet, it is always a good idea to consult with a trusted medical professional. We are not a medical resource. The opinions and articles on this site are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional.

What Is Nitric Oxide?

Nitric oxide is a gas in your body that plays an important role in your vasculature. (1) It’s a free radical with a purpose, lowering cell inflammation and adhesion. Nitric oxide helps relax, widen, and create new blood vessels — ultimately allowing for more blood circulation. (1

Unrestricted circulation can help lower your blood pressure, protect your cardiac health, and increase your cognitive health. (2)(3) In addition to your heart and your brain, nitric oxide helps blood flow to your skeletal muscles which is important when you’re cranking out your muscle and strength-building reps in the gym.

[Read More: Nutrition for Athletes — How to Eat for Muscle and Performance]

Studies have found nitric oxide and exercise physiology to have a mutually beneficial relationship. Nitric oxide benefits strength and cardio exercise, and exercise itself can create more nitric oxide. (4) This is one way that exercise can help lower blood pressure and improve cardiac health. 

Sources of Nitric Oxide

Unlike many other performance-boosting supplements like caffeine and creatine, you can’t consume nitric oxide on its own. However, you can encourage your body to create more of it through nitric oxide synthesis. 

Nitric oxide is synthesized from its precursors L-arginine and nitrates. L-citrulline, a precursor to L-arginine, also contributes. (5) L-arginine and L-citrulline are amino acids that make up muscle protein. Getting all your amino acids through protein intake or other supplements is a key part of nutrition for hypertrophy. (6)

Beets around a glass of beetroot juice.
Credit: Carey Jaman / Shutterstock

[Read More: 20 High-Fiber Foods to Support Digestion]

For nitric oxide synthesis, you can take supplements containing L-citrulline and L-arginine (most common pre-workout supplements and products contain one or both of these) or by eating foods containing these amino acids and nitrates. 

Below are some sources of the nitric oxide boosters L-citrulline, L-arginine, and nitrates:

How Does Nitric Oxide Impact Strength Training?

The primary way that nitric oxide impacts strength training is its role in widening blood vessels and increasing blood flow. More blood flow can help you improve your athletic performance, endure long sessions, and recover more quickly, but the benefits of nitric oxide don’t end there.

Increased Vasodilation

Vasodilation — that is, the expansion of blood vessels — helps deliver oxygen and nutrients to your muscles. Nitric oxide also relaxes and dilates your muscles, and studies have suggested that this may benefit strength athletes. It’s also been shown to aid in muscle growth and performance and induce strength adaptations. (5

Adenosine triphosphate (ATP) helps your muscles contract during short bursts of highly intense activity like powerlifting, jumping, and sprinting. With more ATP, you may be able to improve your athletic performance over time.

Showing up to your workouts ready to focus and perform quality work is key. As you put in the mental and physical work, the nitric oxide in your body may help your blood flow keep up with your efforts.

May Produce a Better Pump

Nitric oxide widens your blood vessels to allow for more blood flow, which can help your muscles appear more vascular and, temporarily, larger. But getting a pump during your workout is not just for bodybuilders. 

Pumped young athletes doing box jumps.
Credit: Daxiao Productions / Shutterstock

[Read More: The Best Foods for Energy Before, During, and After Your Workouts]

Research shows that sending more blood, nutrients, and oxygen to your muscles while training may aid in muscle hypertrophy. The theory is that the increased blood flow delivered more amino acids to your muscles and were more readily available for muscle protein synthesis after exercise. (7)

May Increase Endurance

Nitric oxide may help delay fatigue and increase your endurance. The increased blood flow and nutrient delivery can help you feel energized and withstand longer training sessions. It may help you lift a little heavier for a little longer.

Some studies showed that nitric oxide boosters like beetroot juice and supplements may lower blood pressure and improve performance in long-duration cardio exercise like indoor cycling, walking, and running. (8)(9)

May Improve Recovery

Nitric oxide may help to reduce inflammation and oxidative stress caused by exercise. (1) Better blood flow during and after training increases oxygen delivery to your muscles and may remove metabolic waste, in turn boosting your recovery. Nitric oxide may also help decrease muscle soreness. 

One suspected (but unconfirmed) cause of delayed-onset muscle soreness (DOMS) is a buildup of lactic acid. One study investigated the effect of taking nitric oxide precursors before training by examining the metabolic effect on the athletes after exercise. 

[Read More: Omega 3 Benefits — More Muscle, Better Recovery, and Enhanced Endurance]

The study showed that the athletes who supplemented with nitric oxide precursors had their recovery improved by speeding up the excretion of lactic acid from their bodies. The lactate levels of the nitric oxide supplement group decreased more than the control group. (10)

Side Effects of Nitric Oxide

Note that it’s always wise to consult with your doctor before taking a new supplement. Nitric oxide supplements usually contain L-citrulline and L-arginine and have been reported to cause mild side effects in your head, chest, and gastrointestinal system. (11) These supplements are often not recommended to folks with certain health conditions or taking certain medications. 

The following side effects are caused by dietary supplements — research on nitric oxide for athletic performance shows that the amount of nitric oxide produced from supplements can also be found in foods like leafy greens and beetroot. (11

A person with headache, doing sit-ups.
Credit: – Yuri A / Shutterstock

So, if you’re extra wary of the effect a dietary product may have on your body, you can steer clear altogether and opt for natural sources instead. 

May Excessively Lower Blood Pressure

Nitric oxide is known for helping to lower your blood pressure in part by relaxing your blood vessels. On paper, this may combat the deleterious effects of hypertension. However, nitric oxide supplementation may not be ideal for folks whose blood pressure is already low

Side effects of low blood pressure can include lightheadedness and dizziness. If you are experiencing similar side effects, your nitric oxide supplement may be the culprit.

May Cause Headaches

Improved vasodilation is a benefit of nitric oxide on exercise performance, but too much blood flow may cause headaches. Research on the link between rapid vasodilation and headaches has returned some surprising findings. 

For instance, one proposed theory behind the relationship suggests that nitric oxide can cause blood vessels in your head to dilate too quickly, resulting in an instant headache. (12)

May Create Gastrointestinal Issues

Nitric oxide supplements may cause gastrointestinal issues, including bloating, diarrhea, stomach pain, and nausea. L-arginine and L-citrulline supplements stimulate nitric oxide synthesis, and some of it is produced in your small intestine. (13) Any activity in your small intestine has the potential to cause stomach discomfort, especially if you have a sensitive gut.

[Read More: The 10 Best Probiotic Supplements for Women (2023 Update)]

A review of studies on GI issues after taking L-arginine or L-citrulline showed that side effects occurred after taking more than nine grams of both or either supplement in a single dose. (13) Healthy athletes taking three to six grams did not experience side effects. Folks with diabetes were more likely to experience GI issues at lower doses as well. The review suggests that taking a smaller or divided dose may help avoid GI issues but also notes that more research is needed.

May Affect Medical Conditions

If you are taking blood pressure or diabetes medication, nitric oxide supplements may interact with them in an unexpected way. Medical professionals have reported that nitric oxide supplements could affect health conditions like kidney disease, cardiovascular diseases, cirrhosis, and herpes. (11) In some cases, nitric oxide supplements can also cause an allergic reaction.

A person in pain after working out.
Credit: / Shutterstock

Remember, though, that your body is uniquely yours and that you aren’t necessarily exposing yourself to harmful side effects simply by bolstering your nitric oxide content. Always consult with your healthcare professional about your current condition if you are looking to add a new supplement.

Your Takeaways

Nitric oxide is renowned for its effects on exercise performance, but that doesn’t mean you aren’t taking any risks at all. Here’s all the information you need to know, distilled down to the essentials:

  • Nitric oxide is a gas in your body that helps relax, widen, and create new blood vessels to allow for increased blood flow and vasodilation.
  • Nitric oxide impacts strength training through its ability to increase blood flow
  • Vasodilation delivers more oxygen and nutrients to your muscles to potentially give you a better pump, more endurance, and less muscle soreness after exercise.
  • Potential side effects of nitric oxide supplements include lowering your blood pressure too much, headaches, dizziness, nausea, bloating, stomach pain, and diarrhea. 
  • They may interact with heart and diabetes medications and are not recommended for people with cardiac, kidney, and certain viral diseases.
  • Always consult with your doctor before taking a new supplement.

Wrapping Up

Nitric oxide supplements have the potential to increase your blood flow and lower your blood pressure too much. You may get a headache, feel dizzy, or experience uncomfortable GI distress after taking them. If you have certain medical conditions or are on medications, supplements might interact and worsen your symptoms. 

The good news is that you can still boost your nitric oxide by eating foods with precursors L-arginine, L-citrulline, and nitrates. Grab some beetroot juice and you should be free to feel the pump without the pain as you pound out your reps during your next workout.


  1. Ghimire K, Altmann HM, Straub AC, Isenberg JS. Nitric oxide: what’s new to NO? Am J Physiol Cell Physiol. 2017 Mar 1;312(3):C254-C262.
  2. Kapil V, Khambata RS, Robertson A, Caulfield MJ, Ahluwalia A. Dietary nitrate provides sustained blood pressure lowering in hypertensive patients: a randomized, phase 2, double-blind, placebo-controlled study. Hypertension. 2015 Feb;65(2):320-7.
  3. Paul V, Ekambaram P. Involvement of nitric oxide in learning & memory processes. Indian J Med Res. 2011 May;133(5):471-8. 
  4. Oral O. Nitric oxide and its role in exercise physiology. J Sports Med Phys Fitness. 2021 Sep;61(9):1208-1211. 
  5. Gonzalez AM, Townsend JR, Pinzone AG, Hoffman JR. Supplementation with Nitric Oxide Precursors for Strength Performance: A Review of the Current Literature. Nutrients. 2023 Jan 28;15(3):660. 
  6. Wolfe RR. Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? J Int Soc Sports Nutr. 2017 Aug 22;14:30. 
  7. Biolo G, Tipton KD, Klein S, Wolfe RR. An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein. Am J Physiol. 1997 Jul;273(1 Pt 1):E122-9. 
  8. Lansley KE, Winyard PG, Fulford J, Vanhatalo A, Bailey SJ, Blackwell JR, DiMenna FJ, Gilchrist M, Benjamin N, Jones AM. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol (1985). 2011 Mar;110(3):591-600. 
  9. Wylie LJ, Mohr M, Krustrup P, Jackman SR, Ermιdis G, Kelly J, Black MI, Bailey SJ, Vanhatalo A, Jones AM. Dietary nitrate supplementation improves team sport-specific intense intermittent exercise performance. Eur J Appl Physiol. 2013 Jul;113(7):1673-84. 
  10. Mor A, Yılmaz AK, Acar K, Birinci MC, Ipekoglu G. Does Nitric Oxide Intake Affect Post-Exercise Recovery in Athletes? A Study on Cocoa, Caffeine and Nitric Oxide Supplement: Effect of Nitric Oxide Intake in Athletes. Progr Nutr [Internet]. 2020 Sep.
  11. Kiani AK, Bonetti G, Medori MC, Caruso P, Manganotti P, Fioretti F, Nodari S, Connelly ST, Bertelli M. Dietary supplements for improving nitric-oxide synthesis. J Prev Med Hyg. 2022 Oct 17;63(2 Suppl 3):E239-E245. 
  12. Bagdy G, Riba P, Kecskeméti V, Chase D, Juhász G. Headache-type adverse effects of NO donors: vasodilation and beyond. Br J Pharmacol. 2010 May;160(1):20-35.
  13. Grimble GK. Adverse gastrointestinal effects of arginine and related amino acids. J Nutr. 2007 Jun;137(6 Suppl 2):1693S-1701S. 

Featured Image: Srdjan Randjelovic / Shutterstock

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