If you’ve searched for ways to support healthy circulation, you’ve probably run into nitric oxide (NO) boosters — and CircO2 is one of the more talked-about ones right now. It’s a quick-dissolve tablet sold through the Digistore24 marketplace by Advanced Bionutritionals, built around beetroot nitrate and L-citrulline instead of the plain L-arginine found in older-style NO supplements.

This review breaks down what’s actually in CircO2, what the ingredients are known to do, what the company claims versus what’s reasonable to expect, and who should think twice before trying it. I’ll also flag where the marketing gets ahead of the evidence, because a lot of what’s written about this product online is affiliate copy dressed up as an independent review — and you deserve better than that.

Quick note on affiliate links: This article contains affiliate links. If you buy through them, I may earn a commission at no extra cost to you. That doesn’t change what I actually think of the product — see the full disclosure at the end.

What Is CircO2?

CircO2 is a dietary supplement designed to support the body’s nitric oxide production. Unlike a capsule you swallow, it’s formulated as a fast-dissolving, orange-flavored tablet meant to be chewed or dissolved in the mouth. The idea behind that delivery method is that certain oral bacteria play a role in converting dietary nitrates into nitric oxide, so a sublingual or chewable format may take advantage of that pathway more directly than a swallowed pill does.

The core ingredients are beetroot nitrate and L-citrulline, along with smaller amounts of sodium nitrite, hawthorn berry extract, vitamin C, and vitamin B12 depending on the formulation you see listed.

It’s worth saying plainly: CircO2 is a supplement, not a medication. It isn’t intended to treat, cure, prevent, or diagnose any disease, including high blood pressure or heart disease, and no legitimate seller should claim otherwise.

How Nitric Oxide Works in the Body

Nitric oxide is a naturally occurring signaling molecule your body produces to help regulate blood vessel width. It’s genuinely important physiology — the discovery of its role in cardiovascular signaling earned a Nobel Prize in 1998. In simple terms:

Nitric oxide tells the smooth muscle in blood vessel walls to relax.
That relaxation (vasodilation) allows vessels to widen slightly.
Wider vessels can allow blood — and the oxygen and nutrients it carries — to move more efficiently.

Your body makes nitric oxide through two main pathways: an enzyme-driven pathway that converts the amino acid L-arginine into NO, and a separate pathway that converts dietary nitrates (found in beets, leafy greens, and similar foods) into nitrite and then nitric oxide, with help from bacteria on the tongue. Research suggests natural NO production tends to decline with age, which is the main premise nitric oxide supplements are built around.

Ingredient Breakdown

Here’s what’s typically listed in CircO2, and what’s genuinely known about each ingredient — separate from what the marketing says.

Beetroot Nitrate (Beet Root Powder)

Beets are naturally high in dietary nitrates, which the nitrate-to-nitrite-to-NO pathway relies on. Small clinical studies on concentrated beetroot juice and extract have looked at effects on blood pressure and exercise performance, with some showing modest, short-term improvements in endurance and blood pressure readings. Results vary by study, dose, and individual, and most of this research used concentrated beet juice rather than a low-dose tablet — so it’s a reasonable ingredient to include, but it doesn’t guarantee the same effect at a lower dose in tablet form.

L-Citrulline

This amino acid is converted by the body into L-arginine, which is then used to make nitric oxide via a different enzymatic pathway than the nitrate route. Some research indicates citrulline may raise blood arginine levels more effectively over time than taking arginine directly, since arginine is broken down heavily during digestion. Citrulline has reasonable research support in the context of exercise performance, though effect sizes in studies are often modest.

Sodium Nitrite

Where present, sodium nitrite can convert to nitric oxide more directly and quickly than dietary nitrate needs to. It’s a recognized food-safe ingredient, though anyone monitoring sodium intake should be aware it’s a sodium-containing compound, even in small doses.

Hawthorn Berry Extract

Hawthorn has a long history of traditional use for cardiovascular support and has some clinical research behind it, mostly in the context of mild heart function support, separate from the nitric oxide pathway itself. It’s a reasonable complementary ingredient, though it’s not itself a primary NO booster.

Vitamin C and Vitamin B12

Vitamin C is an antioxidant that may help protect nitric oxide from oxidative breakdown, extending its activity somewhat. B12 supports normal cellular energy metabolism, which is likely why it’s included for the “energy” angle of the product, though B12 itself isn’t part of the nitric oxide pathway.

The honest takeaway: the ingredient list is reasonable and based on real physiology. None of it is exotic or unproven as a category. What’s not established is how well this specific tablet, at this specific dose, performs compared to the research done on higher-dose beet juice extracts or citrulline malate powders — that data isn’t publicly available.

What CircO2 May Help With

Based on the ingredients and how the NO pathway works generally, here’s what’s reasonable to expect — using appropriately cautious language, since none of this is disease treatment:

May help support healthy circulation and blood flow
May contribute to more efficient oxygen and nutrient delivery during exercise
May help support normal energy levels, especially during activity
May support muscle oxygenation and reduce the feeling of early fatigue during workouts
May contribute to general cardiovascular wellness as part of a healthy lifestyle
Some users report subjective improvements in mental clarity, which may relate to nitric oxide’s role in brain blood flow

None of this means CircO2 will lower your blood pressure, treat a diagnosed heart condition, or replace medication. If you have a cardiovascular condition, this is a supplement to discuss with your doctor, not a substitute for their guidance.

Who Should Consider It — and Who Shouldn’t

May be worth considering for:

Healthy adults looking for non-stimulant support for workouts and energy
People interested in a food-based approach to circulation support
Adults over 40 curious about age-related NO decline

Should talk to a doctor first, or avoid:

Anyone currently taking blood pressure medication — combining a vasodilating supplement with BP medication can amplify effects
Anyone taking medication for erectile dysfunction (like sildenafil), since both work on related vascular pathways
Pregnant or breastfeeding individuals
Anyone with a diagnosed heart condition
People sensitive to sodium, given the sodium nitrite content in some formulations

This isn’t a scare tactic — it’s standard, sensible advice for any supplement that affects blood vessel dilation.

How to Take CircO2

Manufacturer instructions generally suggest one tablet daily for general use, or up to two for higher activity levels, chewed or dissolved in the mouth (not swallowed whole) roughly 20 minutes before a meal or workout. Chewing rather than swallowing matters here, since the oral-bacteria step in nitrate conversion happens in the mouth, not the stomach.

Expected timeline: some users report noticing effects within the first one to two weeks of consistent use, with fuller effects — if any — typically assessed over a two-to-three month period, which is also why the product is commonly sold in multi-bottle bundles.

Side Effects and Safety

The individual ingredients are generally recognized as safe by regulatory standards at typical supplement doses. Reported side effects for nitric oxide boosters as a category are usually mild and can include:

Mild stomach upset
Headache (can happen with vasodilation)
Flushing or warmth sensation
Rarely, lightheadedness if blood pressure drops more than expected

Stop use and consult a doctor if you experience unusual dizziness, a significant drop in blood pressure, or any concerning symptoms. As noted above, drug interactions with blood pressure medication and ED medications are the main safety consideration.

Pros and Cons

Pros	Cons
Ingredient list is based on real, studied compounds	No independent clinical trials on this specific product
Chewable/sublingual format may aid absorption via oral bacteria	Effects are generally mild and vary by individual
Non-stimulant — no caffeine-style jitters	Sold only through the manufacturer/Digistore24, not in stores
Multiple positive third-party retailer reviews (Amazon, Walmart listings)	Marketing language on some fan sites overstates benefits
Reasonable safety profile for healthy adults	Not suitable for people on BP or ED medication without medical advice

Price and Guarantee

Pricing and guarantee terms for CircO2 change periodically and vary by bundle size, so rather than quote figures that may be outdated by the time you read this, I’d recommend checking the current price and refund policy directly on the official order page before buying. As of this writing, it’s sold in single-bottle and multi-bottle bundles with a money-back guarantee — confirm the exact window (they’ve varied between 60 and 90 days across different promotions) before you purchase.

Check current pricing

Natural Ways to Support Nitric Oxide

A supplement is only one piece of the picture. These habits are well-supported ways to support your body’s natural nitric oxide production:

Foods: Beets, leafy greens (spinach, arugula), pomegranate, citrus fruits, garlic, and dark chocolate all contain compounds linked to nitric oxide support.

Exercise: Regular aerobic activity is one of the most consistently supported ways to improve vascular function and circulation over time.

Hydration: Adequate water intake supports healthy blood volume and circulation generally.

Sleep: Poor sleep is associated with reduced vascular function, so consistent, quality sleep supports cardiovascular health indirectly.

Avoid antibacterial mouthwash right before or after nitrate-rich foods or NO supplements — it can kill the oral bacteria responsible for converting nitrate to nitrite, blunting the effect.

FAQs

Is CircO2 legit? It’s a real product manufactured by an established supplement company (Advanced Bionutritionals) with GMP-compliant manufacturing claims. That said, “legit” doesn’t mean clinically proven — treat it as a supplement, not a medical treatment.

Does CircO2 really work? The ingredients have real science behind them as a category, but there’s no independent, published clinical trial on CircO2 specifically. Individual results vary.

Is CircO2 safe? Generally considered safe for healthy adults at recommended doses, with important caveats for anyone on blood pressure or ED medication (see the safety section above).

How long until I see results? Some users report noticing effects within one to two weeks; full assessment is usually recommended over 60–90 days.

Can I take CircO2 with blood pressure medication? Talk to your doctor first. Combining any vasodilating supplement with BP medication needs medical oversight.

Is CircO2 good for seniors? The premise — declining natural NO production with age — is real physiology, and the ingredients are generally well tolerated. Still, seniors are more likely to be on medications that interact, so a doctor conversation is especially worthwhile here.

Does CircO2 help with erectile dysfunction? Nitric oxide is involved in that physiology, but CircO2 is not marketed or evidenced as an ED treatment, and it shouldn’t be combined with ED medications without medical guidance.

Is CircO2 vegan? Most listings describe it as plant-derived with no animal-based additives, but check the current label, since formulations can be updated.

Where can I buy CircO2? It’s sold primarily through the official manufacturer site and Digistore24, and has also appeared on third-party retail listings like Amazon and Walmart.

What’s the difference between CircO2 and a beet juice supplement? Beet juice extracts used in research are often higher-dose than what’s in a single tablet. CircO2 combines a lower nitrate dose with L-citrulline and other ingredients to hit the pathway from multiple angles instead of relying on nitrate alone.

Final Verdict

CircO2 is built on a genuinely reasonable set of ingredients for supporting nitric oxide production — beetroot nitrate and L-citrulline aren’t gimmick ingredients, and the chewable delivery format has a real physiological rationale behind it. That’s more than you can say for a lot of products in this space.

What it isn’t is a clinically proven, guaranteed fix for circulation, energy, or heart health. If you’re a generally healthy adult curious about a non-stimulant way to support workouts and daily energy, it’s a reasonable thing to try, especially with a money-back guarantee reducing the downside. If you’re managing blood pressure, heart disease, or take ED medication, this is a “talk to your doctor first” product, not a “try it and see” one.

If you want to try it, check current pricing and the official guarantee here — but go in with realistic expectations, and don’t let anyone (including this article) oversell you on what a supplement can do.

Affiliate Disclosure

This article contains affiliate links. If you make a purchase through one of these links, I may earn a commission at no additional cost to you. This doesn’t influence the honesty of this review — I’ve aimed to represent both the strengths and the limitations of CircO2 fairly, based on publicly available information about its ingredients and how nitric oxide supplementation generally works. This article is for informational purposes only and is not medical advice. Consult a qualified healthcare provider before starting any new supplement, especially if you take medication or have an existing health condition.

CircO2 Review: Does This Nitric Oxide Booster Work? (2026)

CircO2 Nitric Oxide Booster Review: An Honest Look at the Ingredients, Benefits, and Safety

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