CircO2 Reviews 2026: Does This Nitric Oxide Lozenge Really Work?
CircO2 is a sublingual nitric oxide lozenge from Advanced Bionutritionals built around beet root, hawthorn berry, and L-citrulline. Here is what the ingredients, pricing, and real customer feedback actually show.
Quick Summary: Is CircO2 Worth It?
CircO2 is a sublingual nitric oxide lozenge from Advanced Bionutritionals designed to support healthy circulation, energy, and blood pressure using beet root powder, hawthorn berry extract, L-citrulline, and supporting vitamins. It currently holds a 3.9 out of 5 rating from 1,618 verified reviewers on the official site, with 74% saying they would recommend it. One reviewer summed it up simply: it “completely fixed” cold feet within a few weeks, though shipping took longer than expected.
CircO2 is not a drug, does not treat or cure any disease, and results vary from person to person. If you want a fast-dissolving, stimulant-free circulation supplement backed by a 90-day guarantee, it is worth a closer look. If you want overnight results, temper your expectations.
Throughout this review, we’ll walk through exactly what’s in CircO2, how the sublingual lozenge format is supposed to work, what independent nitric oxide research actually says, and what real CircO2 reviews and complaints look like, so you can decide for yourself whether it fits your budget and your health goals.
Overall CircO2 Rating
What Is CircO2 Nitric Oxide Booster?
CircO2 is a nitric oxide supplement made by Advanced Bionutritionals, a longstanding nutraceutical company that manufactures its products in GMP-certified facilities in the United States. Unlike a capsule you swallow, CircO2 comes as a quick-dissolve lozenge that sits under the tongue, which is meant to help the active ingredients absorb through the mouth rather than pass through digestion first.
The formula centers on nitric oxide, a molecule your blood vessels use to relax and widen so blood, oxygen, and nutrients can move more freely. Production of nitric oxide naturally slows with age, which is the gap CircO2 is designed to help fill. If you have compared other circulation formulas, our Endopeak Reviews covers a differently formulated option worth knowing about before you decide.
Who Makes CircO2, and Is the Company Trustworthy?
Advanced Bionutritionals has been operating in the supplement space for years, with a catalog that includes memory, amino acid, and immune support formulas in addition to CircO2. The company states its products are developed with input from doctors, scientists, and nutritionists, and every ingredient supplier is tested for purity before it goes into production. That kind of quality control process is not unique to Advanced Bionutritionals, but it is a reasonable baseline signal when you’re deciding whether a nitric oxide supplement is worth trusting with your money.
One detail that stands out in CircO2 reviews and complaints across independent sites is how consistently reviewers mention the company’s customer service and refund process, even when they weren’t fully satisfied with the results. That combination, being upfront about a 90-day guarantee and generally honoring it, is one of the stronger trust signals you can look for in a crowded nitric oxide supplement market.
CircO2 Key Features
| Feature | Details |
|---|---|
| Brand | Advanced Bionutritionals |
| Format | Sublingual quick-dissolve lozenge |
| Serving Size | 1 lozenge daily |
| Box Contents | 30 lozenges (30-day supply) |
| Stimulant-Free | Yes, no caffeine |
| Manufacturing | GMP-certified, USA facility |
| Diet Compatibility | Non-GMO, gluten-free, dairy-free, vegan |
| Guarantee | 90-day money-back guarantee |
| Where to Buy | Official website only |
| Overall Rating | 3.9/5 from 1,618 reviews |
How CircO2 Works
CircO2 targets the nitrate-to-nitric-oxide pathway that starts in your mouth and continues through your bloodstream. Here is roughly what that timeline tends to look like based on the ingredient research and customer-reported experiences:
Consistency matters here. Nitric oxide production is not a one-time event, it is an ongoing process, so skipping days is one of the most common reasons people say CircO2 stopped working for them. Individual results vary, and none of this replaces medical treatment for diagnosed cardiovascular conditions.
CircO2 Ingredients Breakdown
Beet Root Powder
A natural source of dietary nitrates that the body converts into nitric oxide, supporting vasodilation and blood flow.
Hawthorn Berry Extract
Traditionally used to support heart function and healthy circulation alongside nitric oxide production.
Vitamin B12
Supports red blood cell production, nerve function, and helps manage homocysteine, which matters for vascular health.
Vitamin C
Helps protect nitric oxide molecules from oxidative breakdown so their effects last longer in the body.
Magnesium
Supports relaxation of smooth muscle in blood vessel walls and healthy heart rhythm.
L-Citrulline
Converts to L-arginine in the body, a more efficient route to sustained nitric oxide production than arginine supplements alone.
Sodium Nitrite
A direct nitric oxide precursor that works alongside the plant-based nitrate sources in the formula.
Who CircO2 Is Really For
CircO2 tends to be the most relevant for adults over 40 who are starting to notice the kinds of subtle, easy-to-dismiss changes that come with age-related nitric oxide decline: cold hands and feet, an afternoon energy dip, or the sense that recovery from a workout or a long day takes longer than it used to. It’s also a reasonable option for people specifically looking for a stimulant-free alternative to caffeine-based energy products.
It’s a poorer fit for anyone expecting dramatic, fast results, anyone on a tight supplement budget, or anyone currently on blood pressure medication without having first talked to their doctor. As with most circulation and cardiovascular supplements, CircO2 is meant to work alongside a reasonable diet and activity level, not replace one.
The Science Behind Nitric Oxide Supplements
The core science behind CircO2 is not proprietary to this brand. Dietary nitrates from beet root are well studied for their role in the nitrate-nitrite-nitric oxide pathway, which supports vasodilation. A systematic review of clinical trials on beetroot juice and blood pressure, published through the National Institutes of Health, found that beetroot juice supplementation was associated with measurable reductions in blood pressure across multiple trials. That does not mean CircO2 itself has been clinically tested as a finished product, but it does mean the underlying mechanism has real research behind it.
For a different angle on metabolic and circulatory support, our Glucotonic Reviews looks at a supplement built around blood sugar balance rather than nitric oxide directly.
CircO2 Benefits
Supports Healthy Blood Pressure
By supplying nitrate and nitrite precursors, CircO2 is designed to support the vasodilation process that helps maintain blood pressure already within a normal range.
Boosts Daily Energy Levels
Better circulation means more efficient oxygen delivery to muscles and tissue, which several reviewers connect to steadier energy through the day rather than a caffeine-style spike.
Enhances Blood Circulation
This is the core function of the formula. Reviewers most commonly mention warmer hands and feet and less heaviness in the legs after consistent use.
Improves Cognitive Clarity
Oxygen-rich blood flow to the brain is linked to alertness and focus, which is why several CircO2 reviews mention reduced brain fog.
Supports Cardiovascular Health
Hawthorn berry and magnesium are included specifically to support the cardiovascular system as a whole, not just short-term circulation.
Results vary from person to person, and none of these statements are intended to diagnose, treat, cure, or prevent any disease.
CircO2 Pros, Cons & Side Effects
🌟 Pros
- ✔️ Stimulant-free, no jitters or crash
- ✔️ Full ingredient list disclosed on the label
- ✔️ Fast-dissolving lozenge is easy to use daily
- ✔️ Made in a GMP-certified U.S. facility
- ✔️ Backed by a 90-day money-back guarantee
- ✔️ Non-GMO, gluten-free, dairy-free, vegan
- ✔️ Ingredients supported by independent nitric oxide research
⛔ Cons
- ✖️ No published clinical trial on the finished CircO2 formula itself
- ✖️ Higher price than basic beet powder or arginine supplements
- ✖️ Only sold through the official website, no in-store option
- ✖️ Taste is polarizing for some users during the dissolve phase
- ✖️ Requires daily consistency; skipping days is a common complaint
- ✖️ Not a substitute for prescribed blood pressure medication
Real Customer Experiences With CircO2
Completely fixed my cold feet, but shipping was slow
“Honestly the product itself works really well. I’m 54 and my circulation was getting so bad my feet felt like ice blocks even during summer. Been taking CircO2 for about 3 weeks now and I feel a genuine warmth and energy back in my limbs. Only giving 4.3 stars because delivery took 8 full days to get to my house.”
Great mental clarity, just get used to the taste
“I noticed my afternoon brain fog cleared up within just a few days of letting these dissolve in the morning. I feel way more alert. The only reason I’m knocking off a star is that the citrus-herbal taste is a bit tart and strong when it’s dissolving. It’s not terrible, but definitely takes a few days to get used to it.”
Decent energy lift but a bit expensive
“The ingredient profile (beet root, hawthorn, B12) is high quality and the quick-dissolve system works fast before my workouts. I definitely feel less winded. But man, $50 for a 30 day supply is pretty steep if you are on a tight monthly budget. You really have to buy the 6-pack to make the price reasonable.”
Solid circulation support, don’t skip days
“My daily physical stamina is noticeably better and I don’t feel completely wiped out by 4 PM anymore. Just a quick warning: keep the box where you can see it. I went on a 3 day weekend trip and forgot it, and by Sunday night my sluggishness and heavy legs felt like they were creeping right back. Requires daily commitment.”
Okay results but the lozenge takes time to dissolve
“Word of advice, don’t try to chew it or swallow it whole or it won’t work right. It works nicely for baseline energy, but sitting there waiting for the lozenge to completely dissolve under your tongue every single morning gets a little annoying when you’re in a rush to leave for work. Good formula though if you have the patience.”
Honest analysis: Across these five reviews, the pattern lines up with what the official site’s aggregate rating shows too: strong marks for how CircO2 actually feels to use (energy, warmth, mental clarity), with the main friction points being price, taste, and the daily-use requirement rather than safety concerns.
Where to Buy CircO2 (And Where Not To)
| Package | Price | Per Box | Shipping |
|---|---|---|---|
| 1 Box (30-day supply) | $59.95 | $59.95 | Standard shipping fee applies |
| 3 Boxes (90-day supply) | $159.90 | $53.30 | Free U.S. shipping |
| 6 Boxes (180-day supply) | $249.00 | $41.50 | Free U.S. shipping |
Every order is covered by the 90-day “Down to the Last Lozenge” money-back guarantee: even if you finish the entire box, you can return the empty packaging within 90 days for a full refund, minus return shipping. Always confirm current pricing on the official site, since supplement pricing and promotions change.
When it comes to CircO2 where to purchase questions, the short version is: skip the marketplace listings entirely. Third-party sellers occasionally list older formulations, expired stock, or products that only resemble the real thing, and none of those purchases will be eligible for the official refund policy. Buying direct also means your order is tied to the company’s customer support team if something goes wrong with shipping or billing.
Final Verdict on CircO2
CircO2 is a well-formulated, transparently labeled nitric oxide lozenge that leans on real, published nitrate-and-nitric-oxide research rather than hype-driven proprietary blends. It is not a miracle fix, and the price is genuinely a stretch for some budgets, but the 90-day guarantee makes it close to risk-free to test for yourself. For adults over 40 dealing with sluggish circulation, low energy, or brain fog tied to poor blood flow, CircO2 is a reasonable, evidence-informed option to try.
Check CircO2 Price on the Official SiteHow CircO2 Compares
| Supplement | Format | Key Ingredient | Starting Price |
|---|---|---|---|
| CircO2 | Sublingual lozenge | Beet root + L-citrulline | $59.95/box |
| Neo40 | Dissolvable tablet | Beetroot-based nitrate blend | Varies by retailer |
| N1O1 | Lozenge | Nitric oxide + amino blend | Varies by retailer |
| Standard L-arginine capsule | Swallowed capsule | L-arginine only | Typically lower cost |
What Happens If You Stop Taking CircO2?
Because nitric oxide production through diet and supplementation is not stored long-term in the body, several reviewers noted that benefits like warmth in the extremities and steady energy faded within a few days of stopping. This lines up with how the underlying nitrate-to-nitric-oxide pathway works, it is a daily process, not a one-time boost. If you’re trying CircO2, plan for consistent daily use over at least a full 30-day box before judging whether it’s working for you, and ideally two to three months for the fuller cardiovascular support claims to have a fair chance to show up.
CircO2 Dosage and How to Take It
The standard CircO2 dosage is one lozenge daily. Place it under the tongue and let it dissolve fully rather than chewing or swallowing it, since sublingual absorption is the point of the format. Most official guidance suggests avoiding food or drink for a few minutes afterward and taking it at the same time each day to build consistency.
If you’re wondering does CircO2 work without any other lifestyle changes, most of the customer feedback we reviewed suggests it works best as a complement to reasonable hydration, movement, and a balanced diet, not as a standalone fix.
CircO2 FAQ
CircO2 is a sublingual nitric oxide lozenge from Advanced Bionutritionals made with beet root, hawthorn berry, L-citrulline, and supporting vitamins, designed to support circulation and energy.
The ingredients are backed by independent nitric oxide research, and the majority of the 1,618 official reviews are positive, but individual results vary and there’s no published clinical trial on the finished product itself.
Most users tolerate CircO2 well. Because it can relax blood vessels, people on blood pressure medication, pregnant or nursing women, and anyone with a diagnosed condition should consult a doctor first.
No credible evidence points to CircO2 being a scam. It’s made by an established manufacturer, discloses its full ingredient list, and is backed by a genuine 90-day refund guarantee.
CircO2 is sold exclusively through the official Advanced Bionutritionals website. Third-party listings on Amazon or Walmart may not be the authentic formula.
Not officially. The company recommends ordering directly through their site to guarantee authenticity and guarantee eligibility.
Reported side effects are mild and uncommon, mostly related to taste preference during the dissolve period. Consult a doctor if you notice anything unusual.
Some users report feeling warmer extremities within the first 20 minutes, while fuller benefits like steadier energy and circulation are more commonly reported after 2 to 4 weeks of daily use.
Place one lozenge under your tongue daily and let it dissolve fully rather than chewing or swallowing it.
Dr. Janet Zand has been associated with nitric oxide formulations in this space, but always check the current official Advanced Bionutritionals listing for the exact formula you’re ordering.
As of this review, one box is $59.95, three boxes are $159.90 ($53.30/box), and six boxes are $249.00 ($41.50/box), with free shipping on 3-box and 6-box orders.
Yes, CircO2 is backed by a 90-day “Down to the Last Lozenge” guarantee, allowing a full refund even on an empty box.
CircO2 is generally well tolerated, but because it affects blood vessel relaxation, check with a doctor before combining it with blood pressure medication, blood thinners, or other nitric oxide-boosting supplements.
Yes. CircO2 is formulated to be non-GMO, gluten-free, dairy-free, and vegan.
Final Thoughts
CircO2 earns a fair, if not perfect, recommendation. The ingredient list is disclosed, grounded in legitimate nitric oxide research, and manufactured to real quality standards. The 3.9-out-of-5 rating from 1,618 reviewers reflects genuine, mixed-but-mostly-positive feedback rather than an implausibly perfect score, which is itself a reason to trust it more, not less.
If cold hands, low energy, or circulation concerns sound familiar, and you’re comfortable with a premium price point and a daily-use commitment, CircO2 is a reasonable, research-backed supplement to try, especially with a 90-day guarantee reducing the risk. As always, talk to a healthcare professional if you take medication or manage a cardiovascular condition, and remember that results vary from person to person.
Order CircO2 From the Official Site
Still deciding on CircO2?
Check current bundle pricing and the 90-day guarantee before you go.
View CircO2 Pricing