CircO2 Review: Does It Work? Ingredients Side Effects and Scam Check

As we age, our bodies naturally produce less nitric oxide. Because this molecule is vital for blood vessel health, many people turn to supplements to fight fatigue and poor circulation. This widespread concern is why the search for an honest CircO2 review has skyrocketed. The internet is flooded with supplements promising miracles, so separating science from aggressive marketing is critical.

In this review, we check the actual ingredients, evaluate clinical evidence, investigate side effects, and analyze real customer reviews. We also break down pricing and address recurring scam concerns. We will not offer a final verdict until we look past the sales copy to see if this lozenge actually delivers the cardiovascular support it promises.

Feature	Details
Verdict	Convenient format with proven ingredients, but hindered by hidden dosages.
Best For	Older adults wanting circulation support without mixing powders.
Not Best For	Budget buyers or those wanting clinical-strength transparent dosing.
Evidence Level	Moderate (strong ingredients, but unknown blend amounts).
Price Per Serving	~$1.66 per lozenge.
Side-Effect Risk	Low (mild digestive upset possible).
Refund Policy	90-day money-back guarantee.
Third-Party Testing	Unknown

What Is CircO2 Nitric Oxide Booster?

CircO2 Nitric Oxide Booster is a dietary supplement formulated by Advanced Bionutritionals. The company markets it primarily to men and women over 50 who are experiencing age-related declines in energy and physical stamina. Its main goal is to support the body’s natural production of nitric oxide, a compound that helps relax and widen blood vessels.

Unlike standard capsules or messy drink powders, CircO2 comes as a quick-dissolving lozenge. The manufacturer claims that letting the lozenge melt in your mouth utilizes beneficial saliva bacteria to kickstart the nitric oxide conversion process. The core benefits claimed by the seller include enhanced daily energy, support for healthy blood pressure, better physical endurance, and sharper cognitive function. It is positioned as a daily wellness tool for healthy aging.

CircO2 Claims

Advanced Bionutritionals makes several bold claims on their sales pages. Here is how those manufacturer claims hold up against basic scientific scrutiny:

• Supports Healthy Blood Pressure: Partially Supported. The formula contains beetroot and L-citrulline. According to the National Institutes of Health (NIH), these are known nitric oxide precursors that can support healthy blood flow. However, because CircO2 uses a proprietary blend, we cannot confirm if the dosages are high enough to move the needle.
• Boosts Energy and Stamina: Partially Supported. Better circulation improves oxygen delivery to muscles, which fights fatigue. Users often report feeling more alert, but this is a supportive effect, not a stimulant rush.
• Enhances Memory and Brain Function: Unsupported. While the Mayo Clinic notes that cardiovascular health is linked to cognitive health, claiming this specific lozenge noticeably improves memory lacks direct clinical proof.
• Promotes Immune Health: Supported. It contains Vitamin C and Vitamin B12, which the NCCIH recognizes for supporting general immune function and cellular energy.

Company Behind CircO2

Advanced Bionutritionals is a US-based nutraceutical company located in Norcross, Georgia. They provide clear contact details, including a customer service phone number (1-800-613-5721) and a support email.

Their transparency is mixed. They claim to manufacture products in Good Manufacturing Practice (GMP) certified facilities, and state that CircO2 is vegan, non-GMO, and free of major allergens. However, they do not publish independent, third-party lab testing results for purity and heavy metals on their product pages. They offer a 90-day money-back guarantee, but customer reports indicate that getting a refund often requires persistent follow-up with their support team.

CircO2 Ingredients

CircO2 relies on a “Proprietary Nitric Oxide Blend.” This means the company lists the ingredients but hides the exact milligram amounts of the most important compounds.

Ingredient	Dosage	Claimed Benefit	Evidence Quality	Safety Notes
L-Citrulline	Not disclosed	Boosts nitric oxide levels	Strong	Generally safe.
Beet Root Powder	Not disclosed	Provides dietary nitrates	Strong	Safe; may turn urine pink.
Hawthorn Berry	Not disclosed	Supports blood flow	Moderate	May interact with meds.
Sodium Nitrite	Not disclosed	Direct NO conversion	Limited	Safe in low dietary doses.
Vitamin C	Not disclosed	Antioxidant protection	Strong	Highly safe.
Vitamin B12	Not disclosed	Supports nerve health	Strong	Highly safe.

Note: Without exact dosages for L-Citrulline and Beet Root, it is impossible to know if you are getting a clinical dose or just a “fairy dusting” of ingredients.

How Does CircO2 Work?

CircO2 works by giving your body the building blocks required to create nitric oxide (NO). Nitric oxide signals the smooth muscles surrounding your blood vessels to relax. When these vessels widen, blood flows more efficiently, delivering oxygen and nutrients with less strain on your heart.

The supplement uses two pathways. First, L-citrulline converts to L-arginine in the kidneys, which is then synthesized into nitric oxide. Data from Examine shows this is a highly effective pathway. Second, beetroot powder provides dietary nitrates. When you let the CircO2 lozenge dissolve under your tongue, oral bacteria convert these nitrates into nitrites. Your stomach acid then turns those nitrites into nitric oxide. This specific saliva-activation process is the main reason you must dissolve the tablet rather than swallow it whole.

Does CircO2 Really Work? Evidence Review

When evaluating the evidence, we must separate the ingredients from the actual product formulation.

The ingredients have excellent scientific backing. Numerous studies cataloged on PubMed demonstrate that dietary nitrates (like those in beetroot) significantly raise nitric oxide metabolites in the blood. Similarly, L-citrulline is a heavily researched amino acid proven to enhance circulation and physical endurance.

However, the evidence for the specific CircO2 formula is Weak. The limiting factor is the proprietary blend. Clinical studies that show real cardiovascular improvements usually require 3,000 to 6,000 milligrams of L-citrulline daily. A small lozenge physically cannot hold that much powder. While the sublingual delivery method may increase absorption efficiency, there are no published, peer-reviewed clinical trials proving that the low dosages in a single CircO2 lozenge mimic the results of high-dose clinical studies.

CircO2 Pros

• Science-Backed Core: Uses proven nitric oxide precursors (citrulline and beets).
• Pill-Free Format: Dissolvable lozenges are great for people who hate swallowing capsules.
• Optimized Delivery: Sublingual melting maximizes nitrate conversion via oral bacteria.
• Clean Label: Vegan, non-GMO, gluten-free, and dairy-free.
• Guarantee: Covered by a 90-day return policy.

CircO2 Cons

• Hidden Doses: The proprietary blend hides the exact amounts of the best ingredients.
• Likely Underdosed: A single lozenge cannot hold clinical-level doses of L-citrulline.
• Expensive: At roughly $50 a month, it costs more than high-dose bulk powders.
• No Third-Party Labs: The company does not openly share independent purity testing.
• Billing Complaints: Some users report unwanted auto-shipment charges.

CircO2 Customer Reviews

Real user feedback for CircO2 presents a mixed but generally positive picture. Favorable reviews frequently highlight a gentle, sustained increase in daily energy. Older adults often note that their hands and feet feel warmer, which is a common, subjective sign of improved peripheral blood flow.

Critical reviews rarely mention severe side effects. Instead, negative feedback focuses on the price-to-value ratio. Many users report taking the lozenge for a month and noticing zero changes to their blood pressure readings or stamina. A smaller subset of users complains about the earthy, slightly chalky taste of the dissolving tablet. Overall, customer experiences show this is a mild support tool, not a powerful medical intervention.

CircO2 Reviews and Complaints

Looking at aggregate feedback across the web gives a clearer picture of company trust. Advanced Bionutritionals maintains a profile on Trustpilot, where the brand holds a solid rating, though this covers all their products.

The most common complaints are found on the Better Business Bureau (BBB). Consumers frequently file complaints regarding the company’s auto-shipment program. Many buyers claim they were enrolled in recurring monthly billing without their clear consent and found it difficult to cancel. Additionally, users report that getting a refund under the 90-day guarantee requires persistent emailing and calling, with processing times taking several weeks.

CircO2 Ratings

Reliable public ratings for this specific product are fragmented, but the following reflects available aggregate data.

Platform	Rating	Number of Reviews	Date Checked	Source Note
Trustpilot	4.0 / 5.0	270+	July 2026	Brand-wide rating.
Amazon	~3.8 / 5.0	Varied	July 2026	Sold intermittently by third parties.
Official Site	N/A	N/A	July 2026	Features curated testimonials only.

Side Effects and Safety

The ingredients in CircO2 are generally recognized as safe for healthy adults. Because the product uses a proprietary blend, the actual amounts of L-citrulline and beetroot are likely quite low, making severe side effects rare. However, mild gastrointestinal issues like bloating or stomach cramps can occur. Beetroot powder may also harmlessly turn your urine or stool a pinkish color.

Hawthorn berry is generally safe but can interact with certain medications. According to WebMD, hawthorn can interact with drugs prescribed for heart disease. Because nitric oxide boosters widen blood vessels, they inherently lower blood pressure. Taking this supplement alongside prescription blood pressure medications or erectile dysfunction drugs can cause unsafe drops in blood pressure. The FDA does not review supplements for safety before they are sold, so pregnant women and anyone on prescription medication must consult a doctor first. Based on current FDA recall databases, there are no active safety recalls or public health warnings issued specifically for the CircO2 dietary supplement.

Dosage and How to Use

The official label instructs users to take one lozenge daily. For the best absorption, you should take it in the morning or roughly 30 minutes before physical activity.

You must let the tablet dissolve completely in your mouth. Do not swallow it whole or chew it immediately. The oral bacteria in your saliva are required to convert the nitrates into nitrites effectively. If you swallow the pill whole, stomach acid destroys the nitrates before they can be converted. Do not exceed one lozenge per day unless directed by a healthcare provider.

Where to Buy CircO2

The most secure place to buy CircO2 is directly through the official Advanced Bionutritionals website. Buying direct is the only way to ensure your purchase is covered by their 90-day money-back guarantee.

While you may find listings on Amazon, Walmart online, or eBay, these are often sold by unauthorized third-party resellers. Buying from resellers voids the refund policy and increases your risk of receiving expired or counterfeit products.

Pricing and Refund Policy

CircO2 is priced at a premium compared to generic alternatives.

• 1 Box (30-day supply): $49.95 + shipping ($6.95)
• 3 Boxes: $134.85 (Free shipping)
• 6 Boxes: $249.00 (Free shipping)

This makes the base cost approximately $1.66 per serving.

The company offers a 90-day money-back guarantee, allowing you to return empty or unused boxes for a refund of the product price. However, you must contact customer service directly to authorize the return. Buyers must also pay very close attention at checkout to ensure they do not accidentally opt into the “Subscribe and Save” auto-billing program unless they specifically want monthly deliveries.

Is CircO2 a Scam? Red Flags and Trust Check

CircO2 is not a scam. Advanced Bionutritionals is a legitimate, contactable business that ships a physical product containing science-backed ingredients.

However, consumers should be aware of a few red flags. The use of a proprietary blend prevents you from knowing exactly what you are paying for. Furthermore, the Federal Trade Commission (FTC) strictly monitors supplements for deceptive marketing, and while CircO2 doesn’t cross into illegal territory, its sales pages do heavily imply massive energy and cardiovascular shifts that a low-dose lozenge is unlikely to achieve. Finally, the BBB complaints regarding frustrating auto-shipment cancellations are a genuine trust concern. Proceed with caution and realistic expectations.

Comparison With Alternatives

Feature	CircO2	HumanN Neo40	Snap Beet Root Powder
Format	Lozenge	Lozenge	Powder
Price / Serving	~$1.66	~$1.50	~$1.16
Core Formula	Citrulline + Beets	Proprietary Nitrates	High-Dose Beets
Label Transparency	Proprietary Blend	Proprietary Blend	Fully Transparent
Guarantee	90 Days	90 Days	90 Days

Snap Beet Root provides vastly superior dosages due to the powder format, while Neo40 is a direct lozenge competitor.

Is CircO2 Worth It?

CircO2 might be worth it for older adults who want a mild, natural boost to their circulation and absolutely refuse to drink powdered supplement mixes. The science behind sublingual nitrate absorption is real, and the convenience of a quick-dissolving tablet is excellent for travel or busy mornings.

However, for most people, it is not worth the $50 price tag. The proprietary blend is a dealbreaker for anyone who wants clinical-strength results. If you are looking for serious vascular support for blood pressure or athletic performance, you are much better off purchasing a fully transparent beetroot or L-citrulline powder where you know you are getting the required 3 to 6 grams per serving.

FAQs

Is CircO2 FDA approved? No. Dietary supplements are not approved by the FDA before they hit the market.

Does CircO2 really work for energy? It provides a mild, supportive boost by improving oxygen delivery via blood flow, but it is not a stimulant and will not feel like caffeine.

Are there side effects? It is generally safe, but mild stomach upset can occur. Beetroot may temporarily turn urine pink.

Is CircO2 a scam? No, the company and product are real, but hidden dosages and auto-billing complaints are valid concerns.

How long does it take to work? Some notice a slight energy lift within an hour, but circulatory benefits require weeks of daily use.

Where can I buy it? The official website is the only way to ensure the 90-day guarantee is honored.

Can I take this with blood pressure medication? No. Combining nitric oxide boosters with blood pressure medication can cause unsafe drops in pressure. Consult your doctor first.

Who should avoid CircO2? Pregnant or nursing women, children, and anyone on prescription cardiovascular medications.

Do I swallow the lozenge? No. It must be dissolved completely in the mouth to activate the ingredients properly.

Conclusion

CircO2 Nitric Oxide Booster utilizes proven ingredients like L-citrulline and beetroot to support cardiovascular health. The lozenge delivery system is a smart, convenient way to maximize nitrate absorption without the hassle of mixing powders. However, Advanced Bionutritionals hides their exact dosages behind a proprietary blend, meaning users are paying a premium price for what is likely a low-dose supplement. While customer reviews indicate it provides a mild energy lift, it is not a high-potency medical solution. If you value convenience above all else, it is a safe option to try, but budget-conscious buyers can find stronger, fully transparent alternatives elsewhere.

Disclaimer: This content is for informational and educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting any new dietary supplement.