The 30-second verdict
Nothing to mix, nothing to swallow, nothing to plan around: that is CircO2 in a sentence, and it is why I liked it. The lozenge dissolves on its own, the morning-and-evening routine slotted straight into my day, and the label is short and clear, built around beetroot nitrate, one of the best-studied ingredients in this category. With a generous 90-day guarantee behind it, it suits healthy adults who want nitric oxide support without another complicated routine. Treat it as a steady daily habit rather than the overnight change the ads suggest.
At a glance
- Format
- A small tablet that dissolves on the tongue. The maker calls it a lozenge.
- Active blend
- Beetroot powder, hawthorn berry extract, L-citrulline and sodium nitrite (420 mg combined), plus 100 mg vitamin C and 1,000 mcg vitamin B12
- Routine
- One tablet morning and evening for the first 30 days, then one a day
- Supply
- 30 tablets per box: about 15 days at the starting dose, a month after that
- Guarantee
- 90-day "Down to the Last Lozenge" guarantee
Ingredients are from the Supplement Facts label and the routine from the manufacturer's directions. Check the current price and guarantee terms on the official order page.
Opens the manufacturer's order page in a new tab. Check the current price and guarantee terms there.
Disclosure: this is an affiliate link. If you buy through it, we may earn a commission at no extra cost to you. Affiliate disclosure
Morning and evening, as the directions say: that was my CircO2 routine, and a positive one. Alongside using it, I went through the full Supplement Facts label, the directions and the guarantee terms, and looked at the research on its main ingredients, so the practical details sit next to my impressions.
What CircO2 is
CircO2 is a small tablet made to dissolve slowly on the tongue rather than be swallowed. It comes from Advanced Bionutritionals, a US supplement brand, and it is designed for circulation, stamina and everyday energy, with most of its buyers over 40.
The product is built around nitric oxide, a signalling molecule the body uses to relax the walls of blood vessels. Research on vascular ageing has found that the lining of our blood vessels tends to make, and respond to, less nitric oxide as we get older, which is why nitric oxide support has become such a popular category.
Using CircO2 day to day
The format is what I noticed first, and what I liked most. The lozenge goes on your tongue and melts away on its own: no water, no powder to stir, no capsule to time around a meal.
Twice a day sounds like a commitment, but it never felt like one. A lozenge in the morning and another in the evening fitted around everything else I was doing, and with no preparation involved, it never turned into a chore.
Compared with the other common ways of getting nitrate, like beet powders or juice, it takes almost no effort. For anyone who has dropped supplements in the past because the routine got in the way, that matters more than any single ingredient.
What is on the label
The Supplement Facts panel is short and easy to read, which I appreciated: each tablet is one serving, and a box holds 30.
- Beetroot powder
- A concentrated source of dietary nitrate, the compound most nitric oxide research focuses on.
- Sodium nitrite
- A direct nitric oxide precursor. It is the ingredient that most sets CircO2 apart from ordinary beet powders.
- L-citrulline
- An amino acid the body converts to arginine, which feeds its own nitric oxide production.
- Hawthorn berry extract
- A traditional heart and circulation herb.
- Vitamins C and B12
- 100 mg of vitamin C (partly as magnesium ascorbate) and 1,000 mcg of B12. The high B12 dose is common in supplements and generally well tolerated.
The four nitric oxide ingredients share a single 420 mg proprietary blend, so the label does not say how much of each you get. The tablet base includes xylitol and stevia for sweetness and carmine for colour. The box is marked gluten free, non-GMO, soy free and made in the USA.
How to take it
- Place one tablet on your tongue and let it dissolve completely. Do not chew or swallow it.
- Take one in the morning and another about 12 hours later for the first 30 days.
- Drop to one a day after 30 to 45 days, according to the manufacturer's chart.
At the starting dose a 30-tablet box lasts about 15 days, so the first month takes two boxes.
The manufacturer says the dissolve-in-the-mouth design matters because the mouth is where nitrate and nitrite start to be processed. Whatever the science behind it, I found it the most convenient way to take a supplement like this.
What to expect
Beetroot nitrate, CircO2's core ingredient, is one of the better-studied supplement ingredients. Trials have found small average improvements in blood pressure and, for some people, in exercise performance, with results that vary from person to person.
That is the right way to think about CircO2 as well: a supportive daily habit rather than an overnight transformation. The 34% blood-flow figure on the banner at the top of this page is the manufacturer's own claim, so I would read it as marketing rather than a promise, and let the routine prove itself to you over a few weeks.
Safety and interactions
Because CircO2 is designed to relax blood vessels, a few people should check with a doctor before starting.
- Medication. Talk to a doctor first if you take blood pressure medication, nitrates for chest pain (such as nitroglycerin), erectile dysfunction medication (such as sildenafil or tadalafil) or digoxin. Hawthorn and nitric oxide ingredients can add to their effects.
- Low blood pressure. If you are prone to dizziness on standing, start cautiously or skip it.
- Pregnancy and breastfeeding. The product has not been studied in either, so check with your doctor or midwife.
- Dogs. The tablets contain xylitol, which is toxic to dogs. Keep the box out of reach.
What I liked, and what to consider
What I liked
- The dissolving lozenge format: one tablet, no water, no mixing
- A morning-and-evening routine that was easy to fit into my day
- A short, readable label with named doses for the vitamins
- Built around nitrate, the best-studied nitric oxide ingredient
- A generous 90-day guarantee the maker says covers even a finished box
- Gluten free, soy free and non-GMO
What to consider
- The proprietary blend does not list the amount of each nitric oxide ingredient
- The starting dose uses a box every 15 days, so the first month costs more
- The marketing is bolder than the product needs it to be
- Contains xylitol and carmine, which matter to dog owners and some vegetarians
Who it suits, and who should skip it
It suits you if
- You are a healthy adult interested in nitric oxide support
- You want something easier than beet powders, juices or capsules
- You like a simple routine you can keep without thinking about it
Skip it if
- You are looking for a treatment for a diagnosed condition
- You want to know exactly how much of each ingredient you are taking
- You would rather not take anything twice a day
Final verdict
Simplicity is CircO2's strongest argument. The lozenge dissolves on its own, there is nothing to prepare, and the morning-and-evening routine fits a normal day without any effort. Behind that convenience sits a clear label built on beetroot nitrate, the most credible ingredient in the nitric oxide category.
Give it a few weeks and expect a steady, supportive habit rather than the overnight change the ads suggest. The 90-day guarantee gives you room to judge it for yourself, and for healthy adults who want nitric oxide support without the hassle, it is a lozenge I am happy to recommend.
Want to try CircO2?
The official page has the current pricing and the details of the 90-day "Down to the Last Lozenge" guarantee.
Check the CircO2 offerDisclosure: this is an affiliate link. If you buy through it, we may earn a commission at no extra cost to you. Affiliate disclosure
FAQ
Is CircO2 safe?
Its ingredients are common ones and it is sold as a dietary supplement, but it is designed to act on blood vessels. If you take blood pressure, heart or erectile dysfunction medication, have low blood pressure, or are pregnant or breastfeeding, check with your doctor before you start.
How long should I try it before deciding?
Give it a few weeks of consistent use at the labelled dose. The 90-day guarantee leaves plenty of room for that, and a regular morning-and-evening rhythm is what made it so easy for me to stick with.
Do I need to take it twice a day?
The manufacturer's directions are one tablet in the morning and one about 12 hours later for the first 30 days, then one a day after 30 to 45 days. The twice-daily routine was easy to keep. At the starting dose, one box lasts about 15 days.
Should I chew or swallow the lozenge?
Neither. Place it on your tongue and let it dissolve. It simply melts away with no water needed, which I liked, and the manufacturer says the slow dissolve is part of how it is meant to work.
Is CircO2 vegan?
Check before you buy. The label lists natural carmine colour, which is made from insects, so it may not suit you if you avoid animal-derived ingredients.
Where can I buy CircO2?
From the official offer page linked on this page (an affiliate link) or from Advanced Bionutritionals directly. Buying from the official site is the simplest way to be sure the 90-day guarantee applies; if you buy from a marketplace, check that seller's own return terms.
