Continuous Ketone Monitors in NZ: What They Measure, Who They Suit, and What the Evidence Says
By the Rose Optometry optometrist team, Hamilton. General information only — it does not replace advice from your GP or diabetes team. Numbered references are listed at the end.
A continuous ketone monitor (CKM) is a small wearable sensor that measures the ketone beta-hydroxybutyrate in the fluid just under the skin and sends readings to an app on your phone [1,2]. It is the ketone equivalent of a continuous glucose monitor: instead of a single test, you see a trend.
What are ketones, and what is ketosis?
When glucose is not readily available, the liver turns fatty acids into ketone bodies — mainly beta-hydroxybutyrate and acetoacetate — which the body uses for fuel. Ketones are always present in the blood, normally below 0.5 mmol/L, and rise with fasting and prolonged exercise [3]. Ketosis is the state of having raised ketones. Our keto diet guide covers the diet itself.
Nutritional ketosis is usually described as blood ketones of about 0.5 to 3 mmol/L with normal blood glucose and pH [4]. That is very different from diabetic ketoacidosis (DKA), a medical emergency defined by ketones of 3.0 mmol/L or above together with acidic blood, in people who lack insulin [5]. See ketogenesis vs ketosis vs ketoacidosis.
Ways to measure ketones
| Urine strips | Finger-prick ketone meter | Continuous ketone monitor | |
|---|---|---|---|
| What it measures | Acetoacetate in urine [2] | Beta-hydroxybutyrate in blood | Beta-hydroxybutyrate in interstitial fluid [1] |
| What you see | A rough colour reading, reflecting urine made since you last went [2,6] | One reading at one moment | A continuous trend |
| Limits | In one small study, strips missed ketosis in up to half of people in the middle of the day [7] | Needs a finger prick each time | Accuracy still being established (below) |
A finger-prick blood ketone meter remains the test to rely on if you are unwell.
How accurate are continuous ketone monitors?
The evidence is early and small:
- The first published sensor study, in 12 people on low-carbohydrate diets, found readings within about 0.13 mmol/L of blood ketones at lower levels. It was funded by the sensor's manufacturer, and its authors note that no accuracy standard exists for ketone sensors [1].
- For the KS1 sensor specifically, an independently funded study of seven people found readings drifted downward over the 14-day wear, which the authors thought was more likely the sensor than the body [8].
- In 34 adults being treated for DKA, the same brand of sensor read lower than laboratory ketones in 79% of paired values [9].
No study has shown that wearing a continuous ketone monitor improves health outcomes; experts list this as evidence still needed [2,10].
Who is a continuous ketone monitor for?
- People following a ketogenic or low-carbohydrate diet who want to see whether they are in ketosis and what moves their ketones.
- People who fast or train for endurance and want to see how timing affects their ketones. Reviews have not found that ketogenic diets improve endurance performance [11].
If you have diabetes
Diabetes specialists are studying ketone sensors as an early-warning tool for DKA [2,10]. As of the 2026 international expert recommendations, the consumer ketone sensors people can buy had not been approved by US or European regulators as medical devices, and the experts advise that anyone using one should also have a finger-prick ketone meter and strips [10]. We have not found a study validating the KS1 for diabetes management. If you have diabetes, use a ketone sensor only alongside your diabetes team's sick-day plan, never instead of it.
If you have diabetes and feel unwell — nausea, vomiting, abdominal pain, deep laboured breathing or unusual drowsiness [5] — do not rely on a wearable sensor. Check with a blood ketone meter if you have one and seek urgent medical help. DKA can occur with near-normal glucose in people taking SGLT2 inhibitor medicines [5,12].
Why an optometry practice stocks one
Many of our patients are working on their metabolic health, and long-term glucose control is what protects the retina in diabetes. There are no human trials showing that ketosis itself helps or harms the eye; what the research does and does not show is set out in our referenced guide. If you are tracking glucose as well, our CGM guide explains how glucose control affects your eyes.
The KS1 Continuous Ketone Monitor
The KS1 Continuous Ketone Monitor (NZ$139) sits in our wearables range next to the LinX CGM sensor. Each box contains one sensor. The manufacturer states a 14-day wear time, a reading every five minutes and an IPX8 waterproof rating. ✔ Stock on hand — ships NZ-wide from Rose Optometry, Hamilton.
Common questions
How do I know if I am in ketosis?
By measuring. Blood ketones of about 0.5 mmol/L or above are generally taken to indicate nutritional ketosis [4].
Is a continuous ketone monitor better than a ketone meter?
They do different jobs. A meter gives a blood reading at one moment; a continuous monitor shows the trend without repeated finger pricks, but its accuracy is less well established [1,8,9].
How long does a sensor last?
The KS1 has a manufacturer-stated wear time of 14 days. Each box contains one sensor, so one box is two weeks of monitoring.
How much does a continuous ketone monitor cost in NZ?
The KS1 is NZ$139 from Rose Optometry for one 14-day sensor, with free NZ shipping on orders over $100.
Is a ketogenic diet safe for everyone?
No. See who should talk to a GP first.
References
- Alva S, Castorino K, Cho H, Ou J. Feasibility of continuous ketone monitoring in subcutaneous tissue using a ketone sensor. J Diabetes Sci Technol. 2021;15(4):768-774. doi:10.1177/19322968211008185
- Nguyen KT, Xu NY, Zhang JY, et al. Continuous ketone monitoring consensus report 2021. J Diabetes Sci Technol. 2022;16(3):689-715. doi:10.1177/19322968211042656
- Laffel L. Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes. Diabetes Metab Res Rev. 1999;15(6):412-426. PMID 10634967
- Gershuni VM, Yan SL, Medici V. Nutritional ketosis for weight management and reversal of metabolic syndrome. Curr Nutr Rep. 2018;7(3):97-106 (corrected 2025). doi:10.1007/s13668-018-0235-0
- Umpierrez GE, Davis GM, ElSayed NA, et al. Hyperglycemic crises in adults with diabetes: a consensus report. Diabetes Care. 2024;47(8):1257-1275. doi:10.2337/dci24-0032
- Huang J, Yeung AM, Bergenstal RM, et al. Update on measuring ketones. J Diabetes Sci Technol. 2024;18(3):714-726. doi:10.1177/19322968231152236
- Urbain P, Bertz H. Monitoring for compliance with a ketogenic diet: what is the best time of day to test for urinary ketosis? Nutr Metab (Lond). 2016;13:77. doi:10.1186/s12986-016-0136-4
- Kjær SK, Ridder LOR, Svart M, et al. Continuous ketone monitoring: data from a randomized controlled trial. JMIR Diabetes. 2026;11:e85548. doi:10.2196/85548
- Haas NL, Korley FK, Schneider RM, et al. Continuous ketone monitoring in diabetic ketoacidosis: prospective multicenter method-comparison and feasibility study. Diabetes Technol Ther. 2026;28(9):992-998. doi:10.1177/15209156261428034
- Dhatariya K, Bergenstal RM, Al-Sofiani M, et al. Continuous ketone monitoring for people with diabetes: international expert recommendations on the application of a new technology. Lancet Diabetes Endocrinol. 2026;14(1):82-92. doi:10.1016/S2213-8587(25)00331-6
- Murphy NE, Carrigan CT, Margolis LM. High-fat ketogenic diets and physical performance: a systematic review. Adv Nutr. 2021;12(1):223-233. doi:10.1093/advances/nmaa101
- Peters AL, Buschur EO, Buse JB, et al. Euglycemic diabetic ketoacidosis: a potential complication of treatment with sodium-glucose cotransporter 2 inhibition. Diabetes Care. 2015;38(9):1687-1693. doi:10.2337/dc15-0843