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Nitric oxide has become one of the most marketed molecules in the supplement world, and CircO2 sits right at the center of that trend. It is sold as an easy daily lozenge that supports your body’s own nitric oxide production, with a sales angle that leans hard into feeling decades younger. The product itself is more modest than the headline copy suggests, so the useful question is not “does it make you superhuman?” but “what is actually in it, who does it fit, and is it worth the price?”
This review covers what CircO2 is, the ingredients and their doses, where the marketing outpaces the evidence, and the practical things to check before you buy. We have not run our own clinical testing; what follows is an analysis of the formula, the claims, and the pricing, written to help you decide rather than to push a sale. It is not medical advice.
What is CircO2?
CircO2 is a dietary supplement in the form of a quick-dissolving sublingual lozenge, made by Advanced Bionutritionals, a Georgia-based supplement company. A box contains 30 lozenges (a one-month supply at the suggested one-per-day), and each box typically ships with a small number of nitric oxide test strips that measure salivary nitrite, so you can check a reading before and after use. It is sold online through the vendor’s own funnel rather than in retail stores.
The core idea is straightforward: nitric oxide helps blood vessels relax and widen, and the body’s natural production tends to decline with age. CircO2 is marketed as a convenient way to support that production through diet-derived nitrate and related ingredients. That is a reasonable structure-and-function premise, and it is the honest way to read the product, separate from the louder promises in the sales material.
The “feel decades younger” angle: marketing vs. reality
The single most important thing to understand before buying is the gap between the sales page and what a daily lozenge can realistically do. The funnel frames CircO2 around dramatic age-reversal language and energy you can supposedly feel almost immediately, sometimes paired with before-and-after thermal images. Treat that framing with skepticism. Supporting healthy circulation is a plausible structure-function benefit; reversing aging, fixing serious cardiovascular conditions, or replacing anything your doctor has prescribed is not something a supplement should claim or that you should expect.
Read honestly, CircO2 is a convenience product built around dietary nitrate and a few supporting nutrients. Read through the marketing, it can sound like a medical breakthrough. Going in with the first interpretation will keep your expectations realistic and your money safer.
What’s inside: ingredients and doses
Each lozenge is built around a 420 mg proprietary nitric oxide blend, plus two added vitamins:
- Beetroot powder – a natural source of dietary nitrate, which the body can convert toward nitric oxide. This is the most evidence-aligned part of the formula.
- L-citrulline – an amino acid commonly used in nitric oxide products to support the body’s own production.
- Hawthorn berry extract – a botanical with a long traditional use related to circulation and heart health.
- Sodium nitrite – included as a direct nitric oxide donor; it is also what helps the lozenge act quickly.
- Vitamin C (100 mg) and Vitamin B12 (1000 mcg) – supporting nutrients the marketing ties to nitric oxide metabolism.
The honest caveat is dosing. The 420 mg figure is the whole blend, not any single ingredient, so the amount of L-citrulline per lozenge is well below the doses used in most clinical studies on circulation (which often run into several thousand milligrams). The beetroot-nitrate and sublingual delivery are the formula’s more defensible features; the standalone amino-acid dosing is not where the product competes. Inactive ingredients include mannitol, xylitol, and stevia (sweeteners), plus cellulose, magnesium vegetable stearate, silica, and natural color.
How it works and what to expect
You let one lozenge dissolve under the tongue once a day. The included test strips are a genuinely nice touch: they let you see a salivary nitrite reading rather than guessing, which is more transparency than most supplements offer. Set expectations carefully, though. Any “energy” or circulation effect is individual, often subtle, and not guaranteed; the strips measure a marker in saliva, not a clinical health outcome. This is a daily-habit product, not a one-time fix, and it works best as a small support alongside the basics that move the needle far more (movement, diet, sleep, and managing blood pressure with your doctor).
Benefits, with the reasoning behind them
Sensible core ingredients. Beetroot nitrate, L-citrulline, vitamin C, and B12 are reasonable, widely used choices for a nitric oxide product, so the formula is built on a coherent idea rather than fringe ingredients.
Convenient format. A once-daily sublingual lozenge is easy to stick with, and sublingual delivery is a logical choice for fast-acting nitrate chemistry.
Built-in feedback. The included nitric oxide test strips let you check a before-and-after reading, which is more measurable accountability than typical capsules give you.
Established vendor with a guarantee. Advanced Bionutritionals is a long-running supplement company, and these offers are generally backed by a money-back guarantee, which lowers the financial risk of trying it (verify the current terms before paying).
Honest limitations and downsides
Underdosed actives. The proprietary blend caps total active content at 420 mg, so individual doses (L-citrulline in particular) are far below what studies typically use. If you want a clinically meaningful citrulline or beetroot dose, a dedicated single-ingredient product may give you more per dollar.
Proprietary blend. Because the 420 mg is a blend, the label does not disclose the exact amount of each ingredient, so you cannot fully compare it to alternatives.
Sodium nitrite is polarizing. It is effective as a nitric oxide donor, but some buyers prefer to avoid added nitrites. This is a personal call worth raising with your doctor, especially if you have any cardiovascular condition or take related medication.
Price and recurring billing. Single boxes are not cheap once shipping is added, and the best per-box pricing requires buying in bulk. Subscription or autoship options exist, so it is easy to end up on recurring charges if you are not paying attention at checkout.
Aggressive marketing. The age-reversal framing oversells what a daily lozenge can do, which is worth keeping in mind when you read the sales page’s claims and testimonials.
Who it’s for and who should skip it
Reasonable fit: adults who want a convenient, once-daily nitric oxide support product, like the idea of tracking a reading with test strips, are generally healthy, and have cleared supplement use with their doctor.
Probably skip if: you want a clinically meaningful single-ingredient dose of L-citrulline or beetroot; you prefer to avoid added sodium nitrite; you take blood-pressure medication, nitrates, or blood thinners (talk to your doctor first either way); or you are expecting the dramatic results the marketing implies.
Pricing, refunds, and billing
CircO2 is generally advertised at roughly $49–$60 per box (30 lozenges), with a shipping fee on single boxes and lower per-box pricing on three- and six-box bundles that often include free shipping. Offers usually carry a money-back guarantee. Because the funnel may offer subscription or autoship, confirm three things at checkout before you pay: whether your order is a one-time purchase or a recurring subscription, the exact refund window and how to request a refund, and the current total including shipping. Prices and promotions change, so treat these as ballpark figures and verify the live numbers on the official page.
How it compares to the alternatives
Dietary nitrate from food (beets, leafy greens) is the cheapest way to support nitric oxide and needs no supplement at all, though it is less convenient and harder to measure. Standalone L-citrulline powder gives you a far larger, transparent dose per serving for circulation and exercise support, usually at a lower cost per gram, but without the lozenge format or test strips. Beetroot shots or powders deliver a bigger nitrate dose if that is your priority. CircO2’s pitch is convenience plus the test-strip feedback loop in one daily lozenge, not best-in-class dosing, so judge it on whether that trade-off is worth the premium for you.
What to verify before you buy
- Whether your order is a one-time purchase or a recurring subscription, and how to cancel.
- The current price, shipping fee, and the live refund window.
- That you are on the official offer page.
- With your doctor: that it is safe alongside your medications and any heart or blood-pressure condition.
Our take
CircO2 is a legitimately formulated nitric oxide lozenge from an established company, let down mainly by underdosed actives hidden in a proprietary blend and by marketing that promises far more than a daily lozenge can deliver. The included test strips and the convenient once-daily format are genuine pluses, and the money-back guarantee lowers the risk of trying it. If you want maximum, transparent dosing, a standalone ingredient will likely serve you better for the money. If you value convenience and the feedback loop and you have cleared it with your doctor, it is a reasonable option, provided you go in with realistic expectations and check the billing terms before you order.
See CircO2 on the official offer page
FAQ
Is CircO2 legitimate?
Yes, in the sense that it is a real product from an established supplement company, sold with a stated money-back guarantee and built on recognized nitric oxide ingredients. Whether it fits you depends on the dosing, the price, the billing terms, and your own health situation. Verify the details on the official page and with your doctor.
How is it supposed to be taken?
One lozenge dissolved under the tongue once a day, per the label. The included test strips let you check a salivary nitric oxide reading before and after. Follow the directions on your package and your doctor’s guidance.
Will it put me on a subscription?
It may. Some supplement funnels offer autoship or subscription options that bill on a recurring basis. Read the checkout carefully, choose a one-time purchase if that is what you want, and confirm how to cancel before you order.
Is it safe?
That is a question for your doctor, not a review. Because the formula affects circulation and contains sodium nitrite, it is especially important to check first if you take blood-pressure medication, nitrates, or blood thinners, have a heart condition, or are scheduled for surgery.
How do I get a refund?
Follow the vendor’s refund instructions on your receipt. The refund window shown at checkout applies to your purchase, so confirm it before you buy.
Related reading
- New to this category? Start with what to look for in a nitric oxide supplement.
- For the bigger picture, see our guide to choosing a health supplement.
FDA disclaimer: These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.