Is CircO2 worth it?
Worth a look (4.5/10). CircO2 is built on a real idea: bacteria in the mouth turn nitrate into nitrite, which the body can use to make nitric oxide. The problem is the amount. The four active ingredients share a single 420 mg proprietary blend, while trials on L-citrulline use 3 to 9 grams a day and the beetroot trial used a 250 mL juice drink. The headline numbers ("200% in 20 minutes", "34% more blood flow") come with no study attached, and the label lists sodium nitrite, which the sales copy does not discuss. At $41.50 to $49.95 a month, the price is the price of a promise we cannot check.
What we liked
- Full supplement facts image and a named company with a street address
- Uses a real biological pathway (oral bacteria turning nitrate into nitrite)
- FAQ warns people with low blood pressure to see a doctor
- Free shipping on 3 and 6 boxes
- Refund promise of at least 60 days
What we didn't
- 420 mg proprietary blend of four ingredients, no individual amounts
- L-citrulline and beet amounts far below the ones in trials
- Headline numbers have no study behind them
- Sodium nitrite is not covered in the sales text
- Return shipping is on you, and the page and checkout quote different windows
What is CircO2?
CircO2 is a dietary supplement sold by Advanced Bionutritionals, a Georgia company that also sells a long list of other formulas. It comes as a fast-dissolving tablet, one serving per tablet and 30 tablets per box. The sales page says to place it on the tongue so it can mix with bacteria that convert nitrate into nitric oxide, and suggests two a day for the first week or two, then one a day.
The pitch is that nitric oxide falls sharply with age ("75% by age 70") and that this drop sits behind tiredness, blood pressure concerns, memory lapses, joint discomfort and cold hands and feet. CircO2 is presented as the fix, with beet root powder, hawthorn berry extract and L-citrulline as the three headline ingredients plus vitamins B12 and C and magnesium.
The page is fronted by Dr. Greg Eckel, a naturopathic physician, and carries a disclosure that he is paid by Advanced Bionutritionals for endorsing the product. The offer is sold through Digistore24, which appears on your card statement.
Format: Quick-dissolve nitric oxide tablet, 30 per box, 1 a day (2 a day for the first week or two per the FAQ). Sold by: Advanced Bionutritionals (sold through Digistore24).
What is on the CircO2 label?
Each row compares what the label or sales page states with what published research used. When an amount is missing, there is nothing to compare, and we say so.
One 420 mg "Proprietary Nitric Oxide Blend" holds beet root powder, hawthorn extract, L-citrulline and sodium nitrite together, so the split between them is unknown and the total is smaller than a single gram of L-citrulline alone would be in most trials.
Do the CircO2 claims hold up?
"Nitric Oxide Levels Jump 200% Higher In Just 20 Minutes"
The page says this came from "clinical testing" but names no study, no dose, no group size and no measurement method. We could not tie the number to any published paper. It also credits "MIT scientists" for the oral bacteria idea with no citation. The mechanism itself is real: a 2008 Karolinska study found a nitrate load raised plasma nitrite only when oral bacteria were active. That does not confirm the 200% figure for this tablet.
"L-arginine loses up to 75% of its potency" and L-citrulline is "superior"
Citrulline is a sensible choice and has some blood pressure data. A 2019 meta-analysis found a pooled systolic drop of about 4 mmHg across trials of 3 to 9 g a day. CircO2 puts at most 0.42 g in a blend.
"You don't need to stop" antiseptic mouthwash or fluoride toothpaste
The nitrate pathway depends on oral bacteria. The Govoni 2008 study found a chlorhexidine mouthwash abolished nitrite formation in saliva and cut the rise in plasma nitrite, and a 2015 trial saw blood pressure rise in treated hypertensive people who used it. A tablet that dissolves in the mouth does not change that.
"Healthier blood pressure readings that will impress your doctor"
This is a health outcome promised by the vendor with no data on this product. The FAQ itself warns people with low blood pressure to talk to a doctor first, which is worth taking seriously, and people on blood pressure medicine should do the same.
How much does CircO2 really cost?
| Option | Total | Per month | Shipping |
|---|---|---|---|
| 1 box | $49.95 | $49.95 | Not stated on the page for a single box |
| 3 boxes | $134.85 | $44.95 | Free |
| 6 boxes | $249 | $41.50 | Free |
One box is $49.95 and holds 30 tablets, so at one a day it is $49.95 a month. The 3-box pack is $134.85 ($44.95 a box) and the 6-box pack is $249 ($41.50 a box), both with free shipping. Because the FAQ suggests two tablets a day for the first week or two, a box may last a little under 30 days at the start.
The page leans on the big pack: the 6-box tile says "Biggest Savings" and the text tells you it suggests at least 3 boxes to save $15. The saving from 1 box to 6 is about $8.45 a month, which is small next to the $249 you would put down at once. The August 2026 Digistore24 check showed only the six-box pack on the order form, so make sure you actually see the 1-box option before paying.
The sales page promises a refund within 90 days if you return the box, even empty, and says you pay return shipping. Our checkout data shows 60 days. Either way, the return costs come out of your pocket.
The sales page lists free shipping on the 3-box and 6-box packs and says nothing about shipping on the single box. The Digistore24 order form we checked in August 2026 showed the six-box pack at $249.00 with $0.00 shipping.
Can you get a refund on CircO2?
60-day window. The Digistore24 checkout data we verified gives a 60-day return window, while the sales page advertises a 90-day "down to the last lozenge" guarantee where you send the box back, even empty, and pay return shipping yourself. When two windows are quoted, treat 60 days as the safe one and ask for the 90-day promise in writing before you rely on it. The seller is Digistore24, so refund requests go through Digistore24 support or the vendor.
Step by step: find the Digistore24 order confirmation email, open Digistore24 support and look up the order at digistore24.com/support and ask for a refund in writing. Our Digistore24 refund guide covers returns, extra offers and auto-ship.
Which red flags did we find?
- Proprietary blend hides the dosesFour ingredients share 420 mg with no individual amounts, so nobody can compare them with the research.
- Headline numbers with no study"200% in 20 minutes" and "34% more blood flow" are attributed to clinical testing and "MIT scientists" with no citation.
- Sodium nitrite left out of the copyIt shows on the label image but the ingredient story on the page focuses on beet, hawthorn and citrulline.
- Mouthwash advice contradicts the scienceSaying you can keep using antiseptic mouthwash runs against the study that supports the mechanism.
- Paid doctor and self-hosted reviewsThe doctor is compensated. The 1,618 reviews (3.9 stars, 74% recommend) sit on the seller's own page.
Who should buy CircO2, and who should skip it?
It may suit you if
- You want to try a nitrate-plus-citrulline product, understand the amounts are small and plan to use the refund window if you notice nothing.
- You are comfortable with a vendor that names its company, address and doctor and shows its full supplement facts, even though the blend is not broken down.
Skip it if
- You take blood pressure medication, nitrates for the heart, or erectile dysfunction drugs. Nitric oxide products can add to the effect of these. Talk to your doctor or pharmacist first.
- You want a measurable dose of L-citrulline or beet nitrate. A plain L-citrulline powder or beet product with the amount printed gives you that for less.
- You are watching your budget: $249 is a lot to spend up front on a product with no independent trial.
How we assessed this
We did not buy or use CircO2. This review audits the offer as it appeared on August 24, 2026. We read:
- The CircO2 sales page reached through our Digistore24 affiliate link, including the FAQ, guarantee and bundle boxes
- The supplement facts image on the page (ingredient-label-2025)
- Our Digistore24 checkout verification for product 538695 (price, shipping, return window), August 2026
- Published research: the 2019 L-citrulline blood pressure meta-analysis, the 2015 beetroot juice trial in hypertensive patients and the 2008 mouthwash study on nitrite
Sources
- Effects of L-citrulline supplementation on blood pressure: systematic review and meta-analysis, 2019 (PubMed)
- Kapil et al. 2015, dietary nitrate and blood pressure in hypertensive patients (PubMed)
- Govoni et al. 2008, antibacterial mouthwash and plasma nitrite after a nitrate load (PubMed)
- Digistore24 support (orders and refunds)
Scores: evidence 3, price 4.5, refund 6.5, transparency 4. How we score.
Want a second opinion?
Worthorpass reviews the same offer from the checkout side: the real price on the order form, billing terms and delivery. Read the Worthorpass offer review of Advanced Mitochondrial Formula and compare it with our dose and price audit above.
CircO2 FAQ
Is CircO2 legit?
It is a real product from a named company, sold through Digistore24 with a stated refund. The concern is not that it exists but that the blend hides the amounts, the big numbers have no source and the doses of the main ingredients look small next to the studies.
How much does CircO2 cost?
One box is $49.95, three boxes are $134.85 and six boxes are $249, with free shipping on the larger packs. At one tablet a day, that is $41.50 to $49.95 a month.
What are the CircO2 side effects?
The page says it has had no reports of serious side effects but warns that it relaxes blood vessels and that people with low blood pressure should see a doctor. If you take blood pressure drugs, nitrates or ED medicine, ask your doctor or pharmacist before you start.
How do I get a CircO2 refund?
Use the Digistore24 receipt email and Digistore24 support to open a refund request, or contact the vendor. The page says to return the box within 90 days and pay return shipping, while our checkout data shows 60 days, so ask for the exact terms when you contact them.
What is in CircO2?
Vitamin C 100 mg, vitamin B12 1,000 mcg, magnesium 4 mg and a 420 mg proprietary blend of beet root powder, hawthorn berry extract, L-citrulline and sodium nitrite, plus mannitol, xylitol and other tablet ingredients.
