Continuous sensor vs blood, breath and urine ketone tests
Last checked September 28, 2026
This site gives general information, not medical advice. Talk to your doctor or diabetes team before changing how you monitor or treat any condition.
The four kinds of ketone test don’t just differ in convenience: they measure different ketones in different places, so their numbers can’t be swapped for each other.
| Continuous sensor | Blood meter | Breath meter | Urine strip | |
|---|---|---|---|---|
| Ketone measured | Beta-hydroxybutyrate (BHB) | BHB | Acetone | Acetoacetate |
| Measured in | Fluid under the skin | Finger-prick blood | Breath | Urine |
| Units | mmol/L | mmol/L | ppm (or the maker’s own units) | Color scale |
| Readings | Every 1 to 5 minutes | Each test | Each test | Each test |
| Example running cost | SiBio KS3: £162.92 a month | Keto-Mojo, 1 test a day: $25.85 a month | Ketonix: one-off price, no per-test cost | Ketostix, 1 a day: $7.60 a month |
Continuous sensors
Read BHB in interstitial fluid around the clock and send it to a phone. Abbott’s Libre Duo 10 Day is the first authorized by the FDA (for people with diabetes, not yet on sale); SiBio’s KS3 is sold to adults as a non-medical product. How they work.
Blood ketone meters
A finger-prick on a ketone strip gives a BHB reading in mmol/L. The American Diabetes Association calls a blood ketone meter the preferred way to check ketones (ADA). Blood meters are accurate up to around 3.0 mmol/L but lose precision above about 5 mmol/L (Dhatariya, 2017). Examples: Keto-Mojo GK+, Abbott Precision Xtra and FreeStyle Optium.
Breath meters
Measure acetone in the breath. Studies find breath acetone only moderately correlated with blood BHB, and the metal-oxide sensors used can react to other substances and drift (Fante et al., 2025). Breath ketone meters have no FDA clearance for diagnosis (Huang et al.). Examples: Ketoscan Mini, Ketonix. The once-popular Biosense meter was discontinued in 2024 when its maker closed (report).
Urine strips
Cheap strips that change color with acetoacetate. They use a nitroprusside reaction, give a semi-quantitative result and do not detect BHB at all. During DKA treatment BHB is turned back into acetoacetate, so urine can stay positive while blood ketones fall (Dhatariya, 2017). In people who stay in ketosis for a long time the kidneys reabsorb more acetoacetate, which makes urine strips less reliable (Fante et al., 2025).
For people with type 1 diabetes, and others at risk of diabetic ketoacidosis (DKA), ketone levels are a medical matter. Follow the plan from your diabetes team and the guidance from the NHS or the American Diabetes Association. No consumer ketone sensor replaces the testing your care team asks for.
More guides
- How continuous ketone monitors work
- Ketone levels explained
- Ketone monitors, type 1 diabetes and DKA
- Ketone monitoring on keto diets
- How accurate are ketone monitors?
- Buying in the UK vs the US
Sources
- Dhatariya, Rev Diabet Stud, 2017: blood ketones, measurement and limitations
- Fante et al., Frontiers in Nutrition, 2025: β-hydroxybutyrate testing
- Huang et al., J Diabetes Sci Technol: update on measuring ketones
- American Diabetes Association: DKA and ketones
- Michael Kummer: Biosense review (discontinuation note, Dec 2024)
- Ascensia: Ketostix reagent strips