Prediabetes: the window where a sensor earns its keep
Updated 2026-08-07
Short answer
What should I do about prediabetes?
Prediabetes means glucose above normal but below the diabetes threshold. Between 5% and 10% of people with it progress to diabetes each year — and a similar proportion return to normal glucose levels. Lifestyle change is the intervention with the strongest evidence, cutting progression by more than half in a large randomised trial.
How to read the evidence labels
Every claim on this page carries a label saying how much weight it can hold. The label describes the strength of the finding, not the prestige of the journal it appeared in.
- Strong evidenceA large randomised trial, a long cohort study, or agreement between several of them.
- Emerging evidenceReal, but thin — small, short, observational, or not yet replicated.
- ContestedCompetent researchers actively disagree. We are not picking a side for you.
What the diagnosis actually means
Prediabetes is a threshold, not a disease process: glucose measures higher than normal and lower than the diabetes cut-off. The physiology underneath — insulin resistance together with early beta-cell dysfunction — was under way before the numbers crossed the line.
The word frightens people more than the statistics justify, and it should also not be dismissed. Both halves of the following are true, and popular coverage usually reports only one of them.
What the evidence says
Between 5% and 10% of people with prediabetes progress to diabetes each year, and a similar proportion revert to normoglycaemia.1
Strong evidence
Prediabetes is associated with early nephropathy, chronic kidney disease, small fibre neuropathy, retinopathy and raised macrovascular risk — the harms begin before the diabetes threshold is reached.1
Strong evidence
What actually changes the outcome
The Diabetes Prevention Program randomised 3,234 people at high risk to a lifestyle programme, metformin, or placebo. The lifestyle arm aimed at 7% weight loss and 150 minutes of activity a week. Over an average of just under three years it reduced new diabetes by 58%, beating metformin's 31%.
Put in terms of individual benefit: seven people going through the lifestyle programme for three years prevented one case of diabetes. That is an unusually strong result for a behavioural intervention.
What the evidence says
A structured lifestyle programme reduced progression to type 2 diabetes by 58% and metformin by 31%, compared with placebo, over an average 2.8 years of follow-up.2
Strong evidence
Around seven people had to complete the lifestyle programme for three years to prevent one case of diabetes; for metformin the figure was about fourteen.2
Strong evidence
Where a sensor fits — and where it does not
Notice what was in the trial and what was not. The proven intervention is weight loss and activity. No continuous glucose monitor was involved, and no trial has since shown that adding one improves the result.
The defensible case for wearing a sensor at this stage is narrower and still worth something: it makes an abstract instruction concrete. "Eat fewer refined carbohydrates" becomes a curve you watched change after you walked for ten minutes. That is a plausible aid to doing the thing that works. It is not itself the thing that works, and anyone selling it as such is ahead of the evidence.
A fortnight of wear costs a fraction of a year of it, and for this purpose a fortnight may be all you need. Our cheapest-to-try ranking exists for exactly this reader.
What the evidence says
Common questions
- Can prediabetes be reversed?
- Yes, and it happens often. Roughly as many people with prediabetes return to normal glucose levels each year as progress to diabetes. Lifestyle change substantially shifts those odds in your favour.
- Do I need a CGM if I have prediabetes?
- No. The interventions with proven benefit are weight loss and physical activity, neither of which requires a sensor. A sensor may help you carry them out by making the effect of a meal or a walk visible, but it has not been shown to improve outcomes on its own.
- How long should I wear one for?
- If the goal is learning how your own meals and activity affect you, a single sensor's wear — usually ten to fifteen days — covers most of what you will learn. Continuous wear costs many times more and has no evidence behind it at this stage.
References
- 1.Tabák AG, Herder C, Rathmann W, Brunner EJ, Kivimäki M (2012). Prediabetes: a high-risk state for diabetes development. The Lancet. 10.1016/S0140-6736(12)60283-9
- 2.Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, Nathan DM (Diabetes Prevention Program Research Group) (2002). Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine. 10.1056/NEJMoa012512