Guide
Nitric Oxide Supplements: What Arginine and Citrulline Studies Show
A nitric oxide supplement is usually arginine or citrulline, amino acids the body can turn into nitric oxide. Gram doses lowered blood pressure by about 4 to 5 mm Hg in reviews, but exercise reviews found arginine usually did not change nitric oxide. VapoCept lists 100 to 200 mg per line.
Written by the VapoCept label deskUpdated
The basics01
What is a nitric oxide supplement?
It is a capsule or powder that contains an amino acid the body can convert into nitric oxide, most often L-arginine or L-citrulline. Nitric oxide itself is a gas the body makes, so no capsule contains it.
Nitric oxide is one of the signals that tell blood vessel walls to relax. Reviews of brain physiology describe it as one of the signals that widen vessels supplying the brain (Toda 2009, Nitric oxide and cerebral blood flow). That is lab and animal science about how the body works, not a test of any supplement.
Sellers use the chain "amino acid, then nitric oxide, then wider vessels, then better blood flow". Each link is a proposed mechanism studied mostly in exercise and blood pressure. The links between them were not shown in people for the doses on this site's label.
The proposed pathway02
How are arginine and citrulline supposed to raise nitric oxide?
Arginine is the direct raw material. Citrulline is converted into arginine in the body, so it is sold as a way to supply more. Tap a line in the panel to see its proposed path.
Pathways
200 mg + 200 mg + 100 mg + 100 mg · as listed in the brand's panel
Four of the seven lines (two arginine, two citrulline) feed the proposed nitric oxide route: arginine, or citrulline turned into arginine, is the raw material for nitric oxide, which relaxes blood vessel walls. Studies use grams a day (arginine 2,000 to 24,000 mg, citrulline 6,000 to 8,000 mg), mostly for blood pressure and exercise. The listed amounts are 100 to 200 mg.
Illustration of a proposed mechanism, studied mostly in exercise research. It is not a measured effect on mind, and it is not what happens in your body. Sources: (MSK, Arginine (About Herbs)) (Trexler 2019, Citrulline and strength/power meta-analysis) (ISSN position stand, Beta-alanine) (NIH ODS, Niacin (consumer))
The map shows a proposal, not what happens in your brain. We found no study that measured brain blood flow after VapoCept.
Arginine03
Does arginine increase nitric oxide?
Usually not in the studies reviewed by NIH's Office of Dietary Supplements. Its exercise review reports that arginine typically had no effect on nitric oxide concentration or blood flow (NIH ODS, Exercise and athletic performance (health professional)).
Where arginine does show an effect is blood pressure, at gram doses. A pooled analysis of 11 trials with 387 people, using 4 to 24 g a day, found drops of 5.39 mm Hg (top number) and 2.66 mm Hg (bottom number) (Dong 2011, Oral L-arginine and blood pressure meta-analysis).
Those doses are large. The VapoCept panel, as listed, has 200 mg of L-arginine and 200 mg of L-arginine AKG. Even counting both as pure arginine, 400 mg is 10% of the lowest dose in that analysis.
Mayo Clinic says arginine is not recommended after a recent heart attack because it might raise the risk of death (Mayo Clinic, L-arginine). In a trial of 153 heart attack survivors on about 9 g a day, 6 died versus 0 on placebo, and the trial stopped early (VINTAGE MI trial, L-arginine after heart attack (ACC summary)).
Citrulline04
Does citrulline raise nitric oxide better than arginine?
We cannot say. NIH's ODS says citrulline raised blood markers of nitric oxide, without a clear link to better exercise (NIH ODS, Exercise and athletic performance (health professional)). Evidence for performance is limited and conflicting.
Meta-analyses found small blood pressure drops: about 4 mm Hg on the top number (Yang 2019, L-citrulline and blood pressure meta-analysis). In one of them, the lower number moved only in studies using 6 g a day or more (Citrulline and blood pressure meta-analysis (Avicenna J Phytomed)). The label has 100 mg of citrulline HCl and 100 mg of citrulline malate. That is at most 3.3% of 6 g.
No cited study tested citrulline for thinking, focus or clarity.
VapoCept: 30 capsules, 30-day bottleOne capsule a day · 2, 3 or 6 bottles · $49 to $79 a bottle per the brand information, confirm at checkout
See packsThe numbers05
How do VapoCept amounts compare with studied amounts?
Every amino acid line is a small fraction of the amount studied. The table is our arithmetic from the figures in the sources.
| Line | Label | Studied | Share |
|---|---|---|---|
| L-arginine plus AKG, if both counted as arginine | 400 mg | 4 to 24 g (blood pressure) | 10% or less |
| L-citrulline, both salts | 200 mg | 6 to 8 g | 2.5% to 3.3% |
| Beta-alanine | 40 mg | 4 to 6 g (exercise) | about 1% |
Beta-alanine is not a nitric oxide ingredient at all. It is studied for short, hard exercise. See arginine, citrulline and beta-alanine compared and the dose math page.
Safety06
Who should be careful with nitric oxide supplements?
Anyone who takes blood pressure medicine, a nitrate for chest pain, a sildenafil-type drug or a blood thinner should ask a doctor or pharmacist first.
The reason is additive effects. Arginine can lower blood pressure, and Mayo lists those drug classes as cautions (Mayo Clinic, L-arginine). Memorial Sloan Kettering also repeats the heart attack warning (MSK, Arginine (About Herbs)).
- Keep taking prescribed medicine.
- Stomach upset and bloating are the usual side effects at high doses.
- A supplement is not a drug, and the FDA has not evaluated these statements.
The full list is on side effects. Sudden confusion, trouble speaking or one-sided weakness needs a 911 call, not a capsule.
VapoCept07
Is VapoCept a nitric oxide booster?
The seller's wording, "Clinical Memory Restoration", is not backed by any source we found. We would not call it a booster of anything.
Its panel contains the usual raw materials. Whether 100 to 200 mg of each changes nitric oxide in you has not been tested. Our VapoCept nootropic page compares the seller's claims with the evidence word by word.
- Bottle render“CLINICAL MEMORY RESTORATION”No trial of VapoCept was found, and none of its seven lines has been shown to restore memory at these amounts. 'Clinical' is not a test result. (FTC, Health Products Compliance Guidance) (NCCIH, 7 things to know: supplements and cognitive function)
- Bottle render“FOCUS | CLARITY | ENERGY”Three words, no number. Caffeine and sleep change focus; none of these lines is shown to at 40 to 200 mg. (NCCIH, 7 things to know: supplements and cognitive function)
- Sales page, per the brand's information“Daily mental clarity”A support phrase. The amino acids here are studied for blood vessels and exercise, not clarity, and in grams. (Dong 2011, Oral L-arginine and blood pressure meta-analysis) (Citrulline, perceived exertion and soreness meta-analysis (2020))
- Dose check“200 mg arginine”About 5% of the 4,000 mg a day at the low end of blood pressure trials (4,000 to 24,000 mg). (Dong 2011, Oral L-arginine and blood pressure meta-analysis)
- Dose check“100 mg citrulline”About 1.7% of the 6,000 mg a day at the low end of citrulline studies (6,000 to 8,000 mg); both citrulline lines together are 200 mg. (Citrulline, perceived exertion and soreness meta-analysis (2020))
- Common question“Can it replace my medicine?”No. Keep prescribed medicine. Supplements used in place of medicines are a common route to harm, says NIH. (NIH ODS, Dietary supplements: what you need to know)
- Context“It worked for me”A single story cannot show a capsule did it: sleep, stress, caffeine, a busy week or the wish to feel better all move how sharp a day feels. (FTC, Health Products Compliance Guidance)
Claims as printed on the label. Health claims need competent and reliable scientific evidence, generally human trials of the same product (FTC, Health Products Compliance Guidance).
FAQ08
VapoCept questions people ask
What is the best nitric oxide supplement?
We do not rank products. The better question is the dose: studies of arginine and citrulline use grams a day, while capsules often list far less. Ask a pharmacist if you take blood pressure medicine.
Does arginine increase nitric oxide in the brain?
No study we found shows that. The physiology of nitric oxide and brain vessels is studied in the lab, and exercise reviews say arginine usually did not change nitric oxide or blood flow.
Do nitric oxide supplements lower blood pressure?
At gram doses, arginine and citrulline lowered blood pressure by a few mm Hg in reviews. Smaller amounts have not been shown to do the same. This is why medicine checks matter.
Is citrulline better than arginine?
Citrulline is converted into arginine in the body. Evidence for either on exercise is limited. We found no study proving one is better for thinking, focus or clarity.
How long do nitric oxide supplements take to work?
No source we cite gives a timeline for any thinking effect, because none was shown. Exercise trials ran from a single dose to several weeks. Do not expect a fast result.
Can I take a nitric oxide supplement with nitrates or Viagra?
Ask your doctor or pharmacist first. Mayo lists nitrates and sildenafil-type drugs as cautions with arginine because of additive blood pressure lowering. Do not change a prescription yourself.
Sources (15)
- 7 Things To Know About Dietary Supplements for Cognitive Function, Dementia, and Alzheimer's DiseaseNational Center for Complementary and Integrative Health (NIH), 2026
- Cerebral blood flow regulation by nitric oxide: recent advancesToda N, Ayajiki K, Okamura T. Pharmacological Reviews, March 2009 (abstract via QxMD), 2009
- L-arginineMayo Clinic, 2026
- ArginineMemorial Sloan Kettering Cancer Center (About Herbs), 2022
- Vascular Interaction With Age in Myocardial Infarction (VINTAGE-MI)Schulman SP, et al. JAMA 2006;295:58-64 (summary by the American College of Cardiology), 2006
- Effect of oral L-arginine supplementation on blood pressure: a meta-analysis of randomized, double-blind, placebo-controlled trialsDong JY, et al. American Heart Journal 2011;162(6):959-965 (authors from general knowledge; the fetched page showed only the title, journal and results), 2011
- Effect of oral L-citrulline on brachial and aortic blood pressure defined by resting status: evidence from randomized controlled trialsYang HH, Li XL, Zhang WG, Figueroa A, Chen LH, Qin LQ. Nutrition & Metabolism 2019;16:89, 2019
- Effects of L-citrulline supplementation on blood pressure: A systematic review and meta-analysisBarkhidarian B, et al. Avicenna Journal of Phytomedicine (ajp.mums.ac.ir); authors and year are from general knowledge, as the fetched page showed only affiliations (Iranian universities) and a search date of November 16, 2017, 2019
- Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-AnalysisTrexler ET, Persky AM, Ryan ED, Schwartz TA, Stoner L, Smith-Ryan AE. Sports Medicine 2019;49(5):707-718 (abstract via Duke Scholars), 2019
- Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: A systematic review and meta-analysisJournal of Sport and Health Science 2020 (authors not shown on the fetched PubMed page; Rhim HC et al. from general knowledge), 2020
- International Society of Sports Nutrition position stand: beta-alanineTrexler ET, Smith-Ryan AE, Stout JR, et al. Journal of the International Society of Sports Nutrition 2015;12 (abstract via Northumbria University repository), 2015
- Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health ProfessionalsNIH Office of Dietary Supplements, 2026
- Niacin: Fact Sheet for ConsumersNIH Office of Dietary Supplements, 2021
- Dietary Supplements: What You Need to KnowNIH Office of Dietary Supplements, 2023
- Health Products Compliance GuidanceFederal Trade Commission, 2022
Who wrote this09
Written and reviewed by
Pages built from the brand information, the brand's images and linked NIH, FDA, FTC and peer-reviewed sources.
Last updated . Read our editorial standards and how we check reviews. This website is the information site of Vapocepts, the U.S. stocking partner for VapoCept. It is not the manufacturer and it is not the sales page. We earn money when you buy through our order links.
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