For most adults without diabetes, a continuous glucose monitor (CGM) is an optional purchase. Routine use has not been shown to improve long-term health in this population, and there is no proven universal glucose target for “optimisation”. A CGM can reveal patterns, but deciding what those patterns mean is another matter.
If you are considering one, start with the question you want answered. Curiosity about your daily glucose pattern is different from concern about symptoms or your risk of diabetes.
What does a CGM actually measure?
A CGM uses a small sensor under the skin to measure glucose in interstitial fluid, the fluid between your cells. It estimates glucose levels throughout the day and night, usually sending readings to an app or receiver. It does not directly measure insulin or provide a complete picture of metabolic health. NIDDK explains how CGMs work.
Sensor glucose and blood glucose are related, but they are not interchangeable at every moment. There can be a delay, particularly while glucose is changing. Abbott’s explanation of interstitial glucose describes why simultaneous readings may differ.
What does the evidence say for people without diabetes?
The evidence is developing, with encouraging findings in selected groups and important unanswered questions.
A 12-week randomised trial in people at high risk of type 2 diabetes found that a programme combining an app, lifestyle coaching and intermittent CGM improved some glucose measures and body weight. Because these components were bundled together, the study cannot tell us how much benefit came from the sensor alone. It also did not establish that the programme prevented diabetes.
Larger studies are exploring what glucose patterns might reveal. A 2026 analysis of 3,634 people without diabetes or prediabetes found associations between CGM measures, lifestyle factors and cardiometabolic markers. These associations do not show that wearing a monitor, or changing its readings, improves health. The researchers called for longer-term outcome evidence.
This leaves room for a clinician-supported use in particular circumstances. It does not establish a need for everyone to track glucose continuously.
Does every glucose rise need fixing?
No. Glucose normally changes through the day, including after eating. Exercise and stress can also change the trace. An exploratory study in healthy young adults recorded rises after food, exercise and psychological stress. A rise on a graph is not, by itself, evidence of damage or a reason to avoid a food.
The size and duration of a change, measurement conditions and your wider health context all matter. Research reference ranges and diabetes-management targets should not be treated as a universal wellness score. No validated threshold has been shown to optimise long-term health for every person without diabetes.
How reliable are the readings?
CGMs are useful measurement tools, with limitations. In a 2025 randomised crossover study of 15 healthy adults, the FreeStyle Libre 2 overestimated glucose compared with capillary blood samples during several food and drink tests. The amount of error varied between people and tests. This small study does not describe every device, but it shows why precise-looking readings deserve context.
Pressure on a sensor, such as lying on it during sleep, can also affect readings. Dexcom describes this issue for its G6 system. Follow your particular device’s instructions for unexpected results rather than assuming every apparent high or low is real.
What should you check before buying?
· Purpose: What decision would the information help you make? If you are worried about diabetes, a clinical assessment may answer your question more directly
· Local authorisation: Check the exact product’s intended users and instructions in your country. In the US, some CGMs have FDA clearance for over-the-counter use. In Australia, medical devices generally need inclusion in the Australian Register of Therapeutic Goods unless exempt or excluded. US clearance does not establish Australian authorisation. See the FDA’s current Stelo announcement and TGA guidance on wearables
· Total cost: Include replacement sensors, subscriptions, interpretation services and cancellation terms. Check local reimbursement eligibility separately
· Practical fit: Confirm phone compatibility, sensor wear time, replacement arrangements and available support. Skin irritation and discomfort are possible
· Data and interpretation: Read who can access your data, whether you can export or delete it, and how the provider validates any proprietary score
· Your relationship with tracking: Consider whether frequent numbers would help you or make eating and everyday decisions more stressful
If you have a history of disordered eating, discuss monitoring with a qualified health professional first. The FDA specifically includes this advice for Stelo.
If you decide to try one
Choose a defined purpose and review point before committing to ongoing spending. Record relevant context, such as meals, activity and symptoms, rather than judging an isolated reading. Discuss repeated unexpected patterns with a clinician before changing treatment or making major dietary restrictions.
A CGM does not replace appropriate diagnostic testing. Doctors use blood tests, interpreted alongside your circumstances, to diagnose diabetes and prediabetes. NIDDK’s testing guide explains this distinction. If you feel unwell, seek medical advice even if the app looks reassuring.
You can decide that the information is interesting without making continuous tracking part of your life. For adults without diabetes, the useful question is whether a CGM answers a meaningful question well enough to justify its cost, limitations and effect on your wellbeing.