CircO2 Review: Does This Nitric Oxide Supplement Really Boost Energy and Circulation?

CircO2 Ingredient Analysis

To find out if the ingredients in CircO2 really help with blood flow, stamina, and sexual performance, we took a close look at the formula. Here’s what we discovered:

CircO2 Supplement Fact

Beet Root Powder

Beet root powder is the standout ingredient in CircO2. It is one of the most researched natural sources of nitrates, which the body converts into nitric oxide. Higher nitric oxide levels help relax blood vessels, increase circulation, and deliver more oxygen to muscles and tissues. This is why beetroot has been popular among endurance athletes and men looking to improve stamina.

A study published in the Journal of Exercise Nutrition and Biochemistry found that dietary nitrate from beetroot juice improved exercise efficiency and lowered oxygen cost during physical activity. The participants in that study were able to sustain performance with less fatigue, a clear sign that nitric oxide was working.

This ties directly to CircO2’s claims. Improved circulation not only supports stamina but can also help with sexual performance, as blood flow is a key factor in erections. Based on the evidence, we approve beet root powder.

During our research, we discovered a video by @RenaMalikMD that explains how beet root can improve nitric oxide levels.

L-Citrulline

Next, we have L-Citrulline. This amino acid is often highlighted as superior to L-arginine because it converts to nitric oxide more effectively, especially in men over 40. Stronger nitric oxide production means better circulation, improved blood pressure control, and enhanced sexual performance.

One study in Urology showed that men with mild erectile dysfunction who took L-Citrulline supplementation for one month reported improved erection hardness and satisfaction. The researchers concluded that while it wasn’t as strong as prescription medication, it provided measurable benefits without side effects.

For older men or anyone wanting to support both energy and intimacy, L-Citrulline is a good ingredient.

We approve this ingredient.

According to K Shane Geib, M.D, Urologist and Co-Founder; Men's Sexual Health Specialist

L-Citrulline has shown great potential in improving nitric oxide levels, which can positively affect circulation, blood pressure, and sexual health. Particularly for men over 40, it provides a natural, effective alternative to enhance performance without the side effects associated with prescription medications.

Hawthorn Berry

Hawthorn berry has a long history of use in herbal medicine for heart support, but its role in nitric oxide production isn’t well established. Some evidence suggests it may help with circulation, but the research is inconsistent and not strong enough to support the bold claims made for it here.

A review in Pharmacognosy Review discussed the use of hawthorn for cardiovascular health and noted that results varied widely depending on the preparation and dosage. Importantly, it did not show consistent improvements in nitric oxide or blood vessel dilation. That makes it a weak link in a formula that claims to restore nitric oxide levels.

In our view, hawthorn berry is more of a supportive herb rather than a strong nitric oxide booster. For this reason, we don’t think it deserves a place in this formula. We do not approve.

Vitamin C

Vitamin C is a popular antioxidant, and CircO2 includes it as a catalyst for nitric oxide production and to protect existing nitric oxide from oxidative damage. While this makes sense on paper, the actual impact is modest at best.

Research published in the MDPI Antioxidants (Basel) found that vitamin C supplementation can improve endothelial function (the ability of blood vessels to relax) in people with cardiovascular risk factors. However, these effects were mild and more effective when combined with other interventions.

The problem is that vitamin C doesn’t directly create nitric oxide. Its role is indirect, so the benefits for energy, stamina, or sexual function are limited. A more performance-oriented ingredient, such as Tongkat Ali (Longjack) or Panax Ginseng, often found in top male enhancement supplements like PeakErect, would have been a perfect addition here.

Tongkat Ali (Longjack) and Panax Ginseng are well supported by studies for improving testosterone, energy, and circulation, making them stronger choices for a male-focused supplement. We do not approve of vitamin C.

Magnesium

Finally, we have magnesium. This mineral is essential for many functions, including muscle relaxation, nerve signaling, and maintaining a steady heart rhythm. But its connection to nitric oxide production is weak. While magnesium deficiency can affect cardiovascular health, supplementing it in this way doesn’t directly translate into better stamina or male performance.

A review in the International Journal of Hypertension pointed out that magnesium helps regulate vascular tone and blood pressure, but it works as a general mineral support rather than a targeted nitric oxide booster. For a supplement like CircO2, which positions itself as a fast nitric oxide solution, magnesium feels underwhelming.

Again, more performance-driven ingredients like ginseng or maca would have delivered benefits more aligned with what men are looking for. Magnesium, on the other hand, feels more like a general wellness add-on than a key to performance. We do not approve this ingredient.

We Tried CircO2

We Tried CircO2

Since CircO2 is promoted as a nitric oxide booster for energy, circulation, and even intimacy, we decided to test it ourselves. One person on our team used it for a full month to see if it could make a real difference. He was hoping for more steady energy during the day and some support with stamina and performance.

The instructions were simple: dissolve one lozenge daily. The tablets were small, easy to use, and had a mildly sweet taste. No issues with convenience.

In the first week, there was a slight lift in energy, but it was very subtle. Focus and circulation didn’t feel noticeably different. In terms of sexual performance and libido, there was no real improvement. Things felt the same before and after use.

By the end of the trial, the results had leveled off. No major change in energy, performance, or intimacy was reported. For the price, the impact didn’t match the marketing promises.

CircO2 provided minor benefits, but not enough to stand out. Based on texture, taste, convenience, and results, we would rate it a 5/10.

Similarly, Snap Nitric Oxide Booster claims to enhance circulation and improve stamina. But does it truly deliver on these promises? Read our Snap Nitric Oxide Booster review to discover its effectiveness.

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Side Effects & Safety of CircO2

CircO2 is made with nutrients like beet root powder, L-citrulline, hawthorn berry, vitamins, and magnesium. It does not contain caffeine, stimulants, or synthetic hormones, which makes it a non-intimidating option for most adults.

That said, some users have reported side effects. Alongside complaints of no noticeable results, feedback on Amazon mentioned vertigo, swollen lips, throat tightness, increased blood pressure, and stomach upset. Others noted mild headaches or discomfort during the first few days of use.

While the formula is generally safe for most people, CircO2 may not be suitable for those with blood pressure concerns, heart conditions, or individuals taking prescription medications for circulation. Anyone with chronic health issues should consult a healthcare provider before using this supplement.

CircO2 appears safe for many adults, but results and side effects vary from person to person.

What Do Real Reviews Reveal About CircO2?

Amazon is often a more reliable place to look for customer feedback than a brand’s official website, as it shows verified purchases and unfiltered opinions.

At the time of this review, CircO2 holds a 4 out of 5 star rating on Amazon, based on 406 global reviews. Many users report small boosts in energy and circulation, while others note little to no changes even after completing multiple boxes.

A top positive review from a verified purchaser, Carol H Janak, who gave the product a 5/5 rating, states:

It made a noticeable difference. It is easy to take and I definitely feel a difference, it gives me a nice little boost.

A top negative review from another verified purchaser, Montane_perro, who gave the product a 1/5 rating, states:

Doesn't work. Tried 2 boxes. No improvement at all in my low energy level. Cancelled my subscription. The product ad on the internet is false.

Beyond Amazon, the brand does not currently have a rating with the Better Business Bureau (BBB). On TrustPilot, CircO2 and the company behind it hold a 3.9 out of 5-star average, with mixed experiences shared by customers.

Overall, customer feedback on CircO2 is divided. Some report modest energy support and easier circulation, while others feel no difference at all. This suggests the product may work for certain individuals, but its effects are far from consistent.

Where to Find the Best Value

CircO2 is available on the official website and Amazon. Each box contains a supply of lozenges designed for daily use.

From the official website:

• One box: $49.95
• Three boxes: $44.95 each + Free Shipping
• Six boxes: $41.50 each + Free Shipping

Every order comes with a 90-day satisfaction guarantee, though customers need to cover return shipping.

From Amazon:

• One-time purchase: $59.95
• Subscribe & Save: $53.95

CircO2 is reasonably priced compared to many other circulation and performance supplements. Buying directly from the official website is the better option since you get lower per-box pricing, free shipping on larger orders, and direct access to the brand’s refund guarantee.

CircO2 Vs Flawless Bloom PeakErect

If you have been searching for supplements that promise stamina and performance, you have likely noticed how different the formulas can be.

CircO2 is centered on nitric oxide support. With beet root powder and L-citrulline, it does a fair job at improving circulation, which can help with energy and endurance. But once you look past those two ingredients, the rest of the blend feels more like something from a general health product than a true performance formula. For men hoping to see stronger results in stamina, libido, and confidence, the formula may feel limited.

PeakErect, on the other hand, is built with those exact expectations in mind. Instead of concentrating mainly on circulation, it combines proven performance ingredients such as Longjack, Maca, Panax ginseng, Tribulus, and Muira Puama. These are well known for their links to testosterone support, sexual suppor, endurance, and sexual vitality. With added circulation support from L-arginine, the formula works from multiple angles, making it more complete and more suited to men who want noticeable changes.

Looking at both side by side, CircO2 provides a modest lift in circulation while Flawless Bloom PeakErect delivers a more comprehensive approach to male performance. For men who want support that goes beyond basic stamina, PeakErect offers the stronger formula.

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Pros & Cons of CircO2