Beetroot powder
Provides dietary nitrate, which is part of the nitrate-nitrite pathway the formula is built around.
A closer look at CircO2
Nitric oxide support, made easy to fit into your day.
Meet CircO2 from Advanced Bionutritionals: a caffeine-free, quick-dissolve lozenge for nitric oxide support. No shaker or powder required.
One tablet per serving on the label reviewed. Follow the current package directions.
No caffeine
in the formula
in the formula
Quick-dissolve lozenge
Customer feedback, at a glanceFigures displayed on the manufacturer's site when checked in October 2026.
★★★★☆ 3.9Average rating
1,618Reviews displayed
74%Recommend on the product page
The short version
A small change to the routine. A formula worth looking at closely.
If you have been reading CircO2 reviews 2026 or CircO2 nitric oxide supplement reviews, the most useful details are often the practical ones: how you take it, what the label actually lists, and how much of the evidence applies to this exact product.
This CircO2 review keeps the focus on those details, rather than treating a supplement as a shortcut or promising a result.
Our take: CircO2 stands out for its easy lozenge format and caffeine-free profile. Its main trade-off is a proprietary blend that does not show the separate amount of every active ingredient.
No shaker, scoop, or capsule to swallow
The tablet is designed to dissolve in your mouth, making the format simple to carry and easy to work into a daily routine.
Built around nitric oxide support
The formula combines beetroot, hawthorn, L-citrulline, and sodium nitrite in a blend chosen for nitric oxide-related pathways.
No caffeine listed
For people who prefer to skip stimulant-style energy products, CircO2 is presented as a caffeine-free option.
A simple look at the pathway
Nitratefrom dietary sources
Nitritewith oral bacteria
NOa signaling molecule
This is a simplified description of one biological pathway. It is not a guarantee of a particular effect from a supplement.
How it works
A lozenge approach, instead of another scoop.
Nitric oxide helps signal the normal relaxation of blood vessels. In the nitrate-nitrite pathway, certain bacteria in the mouth can help convert nitrate into nitrite, which the body can then use in nitric oxide production.
CircO2 is designed to dissolve in the mouth and brings several ingredients associated with that broader pathway together in one tablet. The science behind the pathway is interesting. It does not mean the exact CircO2 formula has been proven to deliver a specific outcome for every user.
What's on the label
A quick tour of the CircO2 formula.
The product information reviewed lists familiar nutrients alongside a four-ingredient nitric oxide blend.
Caffeine-free
Hawthorn berry
Included in the product's proprietary blend. The label does not list its individual amount.
L-citrulline + sodium nitrite
Two more ingredients named in the nitric oxide blend. Their separate doses are not disclosed.
Everyday nutrients
Each listed serving also includes vitamin C, vitamin B12 as methylcobalamin, and magnesium.
The label detail to know: Beetroot powder, hawthorn berry extract, L-citrulline, and sodium nitrite are grouped in a 420 mg proprietary blend. The listing reviewed also shows 100 mg vitamin C, 1,000 mcg vitamin B12, and 4 mg magnesium per serving. Individual blend amounts are not listed, so direct dose-by-dose research comparisons are difficult. Check the current Supplement Facts panel before ordering.
CircO2 customer reviews
What buyers are saying, with the right context.
The manufacturer's page displays a steady stream of customer feedback. The score gives you a snapshot of buyer sentiment, not a prediction of what you will experience.
Themes in buyer feedback
Easy to takeSome customers mention that they appreciate the dissolvable tablet and convenient routine.
Energy and staminaSome reviews describe personal impressions of day-to-day energy or workout stamina.
Mixed experiencesAs with any supplement, buyers do not all describe the same experience or timeline.
What reviews can't proveSeller-hosted testimonials are anecdotes, not controlled evidence or a promise of typical results.
“Easy to take and a pleasant taste.”
One customer comment displayed on the manufacturer's page
The customer review count, rating, and recommendation figure are displayed by the manufacturer. Customer statements are personal experiences and may not reflect typical results.
A practical fit check
Are nitric oxide supplements worth it for you?
There is no single best nitric oxide supplement for everyone. If you are asking what is a good nitric oxide supplement or whats the best nitric oxide supplement, start with your preferences, label transparency, and the evidence for the exact product.
You want convenience without caffeine.
You prefer a ready-to-use lozenge over powders or drinks, want a product positioned for nitric oxide support, and are comfortable with the information shown on the label.
You need transparent amounts for every ingredient.
The four central ingredients are in a proprietary blend. If you want to compare each active dose with specific studies or choose exact amounts yourself, that may be a reason to keep looking.
Packages and guarantee
Compare the options before you decide.
These prices were displayed on the official page when checked in October 2026. The seller may change prices, shipping, and package availability.
Price snapshot
October 21, 2026
1 box · 30 tablets
$49.95
$49.95 per box
Lowest upfront cost for a first order.
3 boxes · 90 tablets
$134.85
$44.95 per box
Free shipping was shown with this package.
6 boxes · 180 tablets
$249
$41.50 per box
Free shipping was shown with this package.
90-day satisfaction guarantee advertisedReturn shipping is the customer's responsibility. Review the current terms before checkout.
Good questions, clear answers
Before you add it to your routine.
A few things are worth checking before choosing any circulation-focused supplement.
How do you take CircO2?
The product information describes a flavored lozenge intended to dissolve in the mouth. One serving is listed as one tablet in the information reviewed. Follow the directions on the current package, and do not take more than directed.
How quickly should I expect to notice something?
There is no reliable timeline that applies to everyone. The company's customer stories describe different experiences, but testimonials are individual reports and cannot predict your result. Avoid treating a supplement as a quick fix for a health concern.
Is CircO2 caffeine-free?
The product information reviewed describes CircO2 as caffeine-free. Check the current Supplement Facts panel and other package details if you have an allergy, sensitivity, or ingredient restriction.
Are nitric oxide supplements safe for everyone?
No supplement is right for every person. The manufacturer advises people with low blood pressure to consult a physician before use. If you take medication, have a cardiovascular condition, or are pregnant or breastfeeding, check with a qualified healthcare professional or pharmacist first.
Can CircO2 replace medication or medical care?
No. CircO2 is a dietary supplement, not a substitute for prescribed medication, diagnosis, or care. Talk with a clinician about persistent symptoms or changes in blood pressure, circulation, energy, or sexual function.
Has the exact CircO2 formula been clinically tested?
The research discussed in the accompanying review includes a small study of a different named oral nitric oxide product, not the current CircO2 formula. That may be relevant to the broader delivery concept, but it is not direct clinical proof for CircO2 or a guarantee of a particular result.
What does the 90-day guarantee cover?
The official page advertises a 90-day satisfaction guarantee and says return shipping is the customer's responsibility. Policies can change, so read the current terms and return instructions on the official page before ordering.
Make an informed choice
If the format fits, take one last look at the details.
Review the latest CircO2 Supplement Facts, package options, shipping, and refund terms on the manufacturer's site. Then decide whether the formula feels right for your routine.
Review the official CircO2 offerPrices and terms may change. Always confirm the current details before purchase.