Prediabetes tests: what the label means and what helps
Updated: 4 hours ago
The short answer
Prediabetes can be diagnosed by fasting glucose, A1c or a glucose-tolerance test, and those tests do not always label the same people. The label does not mean diabetes is inevitable: in a study of older adults, many more people returned to normal or stayed stable than developed diabetes over five years. In the largest prevention trial, an intensive lifestyle program reduced diabetes incidence more than metformin during the original trial. Which test gave you the label, your age and the direction of your results matter when you decide what to do next.
What we cover
The three tests and their different time windows: one fasting sample, a longer-term blood-sugar average and a response to a glucose drink. Guideline
What happened when fasting glucose and A1c were checked in the same 3,412 older adults: 59 percent qualified by fasting glucose, 44 percent by A1c, and 29 percent by both. Primary source
The five-year outcomes by test, including the greater likelihood of returning to normal fasting glucose than progressing to diabetes in that older population. Primary source
The lifestyle dose that beat metformin: a 7 percent weight-loss goal and at least 150 minutes of activity each week, delivered with structured support. Primary source
The actual event counts behind the 58 percent relative reduction, and why a percentage needs its baseline. Primary source
What 21 years of follow-up showed about diabetes delay, and what the study did not establish about every later health outcome. Primary source
Why two results and their trend help more than treating one label as a countdown. Primary source
Timestamps
0:00 There is no single prediabetes test
1:49 The three doorways, and why they disagree
2:23 Your real odds, by which test
3:49 What the label actually predicts
4:12 Glucose checked twice, eleven years later
5:14 Pill, or lifestyle?
6:12 The two targets, and what they take
6:34 The plate that gets you there
8:11 The plain counts, before the percentages
8:37 Why 58 percent misleads
9:11 Where the drug barely worked
10:13 Twenty-one years later
11:45 What one normal reading tracked with
13:21 What to do this week
13:53 One line on medication
References
American Diabetes Association. Standards of Care in Diabetes 2026. Diabetes Care 2026;49(Suppl 1). Section 2, Diagnosis and Classification, S27-S49, https://doi.org/10.2337/dc26-S002 Section 3, Prevention or Delay of Diabetes, S50-S60, https://doi.org/10.2337/dc26-S003
Defines the diagnostic tests and gives prevention recommendations for people at increased risk of diabetes. Evidence type: clinical guideline.
Rooney MR, et al. Risk of progression to diabetes among older adults with prediabetes. JAMA Internal Medicine 2021;181(4):511-519. https://doi.org/10.1001/jamainternmed.2020.8774
Over five years, 8 percent of older adults with impaired fasting glucose developed diabetes and 44 percent returned to normal fasting glucose. Evidence type: observational cohort.
Chen G, et al. Impact of the longitudinal evolution of impaired fasting glucose on cardio-kidney-metabolic multimorbidity. Frontiers in Endocrinology 2026;17:1812122. https://doi.org/10.3389/fendo.2026.1812122
Longitudinal glucose patterns were associated with later cardio-kidney-metabolic multimorbidity rather than proving that one test caused it. Evidence type: observational cohort.
Knowler WC, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine 2002;346(6):393-403. https://doi.org/10.1056/NEJMoa012512
The structured lifestyle intervention reduced diabetes incidence by 58 percent and metformin by 31 percent relative to placebo. Evidence type: randomized trial.
Knowler WC, et al. Long-term effects and effect heterogeneity of lifestyle and metformin interventions on type 2 diabetes incidence over 21 years in the US Diabetes Prevention Program randomised clinical trial. Lancet Diabetes and Endocrinology 2025;13(6):469-481. https://doi.org/10.1016/S2213-8587(25)00022-1
Long-term follow-up found sustained differences in diabetes incidence after the original prevention interventions. Evidence type: follow-up of a randomized trial.
Perreault L, et al. Effect of regression from prediabetes to normal glucose regulation on long-term reduction in diabetes risk: results from the Diabetes Prevention Program Outcomes Study. Lancet 2012;379(9833):2243-51. https://doi.org/10.1016/S0140-6736(12)60525-X
Returning to normal glucose regulation was associated with lower subsequent diabetes risk. Evidence type: observational analysis of trial follow-up.
One study explained in plain language every week, with sources attached, plus the free metabolic health guide: https://guides.selfprinciple.org/metabolic
This content is for educational purposes only and is not medical advice. Always consult your healthcare provider for individual care. The views expressed are Dr. Sean Hashmi's own and do not represent his employer.
Never start, stop, or change the dose of any prescription medication without consulting your physician.
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