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Metabolic Health and Blood Sugar: Prediabetes, Glucose Monitors and Supplements, by the Evidence

Lifestyle change cut new diabetes by 58% in the landmark prevention trial, more than metformin. Over-the-counter glucose monitors are now FDA-cleared, but their benefit for people without diabetes is unproven, and most blood sugar supplements were tested in people who already had diabetes.

By Kymata Health editorial teamLast verified October 10, 2026

Medical review pending. Written by our editorial team from the studies and documents cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • In the Diabetes Prevention Program (3,234 adults with prediabetes-range glucose), a lifestyle program cut diabetes incidence by 58% and metformin by 31% vs placebo over 2.8 years [1].
  • After 15 years of follow-up, diabetes incidence was still 27% lower in the original lifestyle group and 18% lower in the metformin group, with the gap narrowing over time [2].
  • The FDA cleared the first over-the-counter continuous glucose monitor, Dexcom Stelo, on March 5, 2024 for adults 18+ who do not use insulin [3].
  • A 2026 systematic review found that visible CGM data may support some diet changes in people without diabetes, but large, lasting or stand-alone benefits are not established [4].
  • Psyllium, berberine and chromium lowered glucose mainly in people with diabetes or high glucose; chromium showed no effect in people without diabetes [5][6][7].

Guides in this hub

  1. Prediabetes: Lifestyle Change Beat Metformin in the Landmark Trial. Here Are the NumbersIn the Diabetes Prevention Program, a lifestyle program cut new type 2 diabetes by 58% and metformin by 31% over about 3 years. Fifteen years later both groups still had less diabetes than placebo.
  2. Do You Need a Continuous Glucose Monitor Without Diabetes? What the FDA Cleared and What Studies ShowOver-the-counter glucose monitors are FDA-cleared for adults not on insulin. A 2026 systematic review found they may nudge some diet changes as part of structured programs, but stand-alone benefit is not established.
  3. Blood Sugar Supplements vs Placebo: Berberine, Psyllium and ChromiumBerberine, psyllium and chromium lowered glucose in trials of people with type 2 diabetes. In people with normal glucose the effects shrink or vanish, and some blood sugar products have contained hidden drugs.

Where to start

The best-tested way to keep prediabetes from becoming type 2 diabetes is a structured lifestyle program aiming for at least 7% weight loss and 150 minutes of activity a week; it outperformed metformin in the Diabetes Prevention Program [1]. Our prediabetes guide covers the trial and what it means.

Gadgets and supplements come after that. A continuous glucose monitor can show how meals affect your glucose, but the evidence that it changes outcomes in people without diabetes is thin [4]. Our CGM guide covers the FDA clearance and the trials.

Supplements: tested mostly in people with diabetes

Psyllium lowered fasting glucose and HbA1c in a 2024 meta-analysis of 19 trials [5], and an earlier meta-analysis found the effect scaled with how high glucose was to begin with, with no significant lowering in people with normal glucose [6]. Chromium lowered HbA1c in trials of people with type 2 diabetes [7] but showed no effect on glucose or insulin in people without diabetes [8].

The American Diabetes Association says there is not enough evidence to recommend magnesium for glycemic control [9]. Our supplement guide covers berberine, psyllium and chromium in detail.

Partners we link to

Paid links: we earn a commission if you buy through these, at no extra cost to you. It never changes what the evidence sections say. Affiliate disclosure.

  • FoundPaid linkWeight care with named board-certified clinicians: brand-name GLP-1 prescriptions (medication billed separately, insurance accepted) or compounded semaglutide and tirzepatide, which are not FDA-approved. LegitScript certified.See Found's weight plans

Regulatory and legal notes

  • Dexcom Stelo was cleared on March 5, 2024 as the first over-the-counter CGM, for adults 18+ not on insulin and not for people with problematic hypoglycemia; the FDA says users should not make medical decisions from it without talking to a clinician [3].
  • In December 2024 the FDA warned consumers not to buy Fouzee SugarLin Herbal Formula, a blood sugar support product that FDA testing found contained undeclared metformin and glyburide [10].
  • Dietary supplements cannot legally claim to treat or prevent diabetes; the FDA has warned that products promoted as natural blood sugar aids can contain hidden prescription drugs [10].

References

  1. [1]Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med, 2002. PMID 11832527
  2. [2]Long-term effects of lifestyle intervention or metformin on diabetes development and microvascular complications over 15-year follow-up: the Diabetes Prevention Program Outcomes Study. Lancet Diabetes Endocrinol, 2015. PMID 26377054
  3. [3]FDA Clears First Over-the-Counter Continuous Glucose Monitor. U.S. Food and Drug Administration, 2024.
  4. [4]Behavioral and Psychosocial Effects of Participant-Visible Continuous Glucose Monitoring in Adults Without Diabetes: A Systematic Review. Medicina (Kaunas), 2026. PMID 42796420
  5. [5]The effect of psyllium on fasting blood sugar, HbA1c, HOMA IR, and insulin control: a GRADE-assessed systematic review and meta-analysis of randomized controlled trials. BMC Endocr Disord, 2024. PMID 38844885
  6. [6]Psyllium fiber improves glycemic control proportional to loss of glycemic control: a meta-analysis of data in euglycemic subjects, patients at risk of type 2 diabetes mellitus, and patients being treated for type 2 diabetes mellitus. Am J Clin Nutr, 2015. PMID 26561625
  7. [7]Effects of chromium supplementation on glycemic control in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials. Pharmacol Res, 2020. PMID 32730903
  8. [8]Glucose and insulin responses to dietary chromium supplements: a meta-analysis. Am J Clin Nutr, 2002. PMID 12081828
  9. [9]Magnesium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2026.
  10. [10]Fouzee SugarLin Herbal Formula may be harmful due to hidden drug ingredients. U.S. Food and Drug Administration, 2024.

Dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Prescription options need a licensed clinician. Talk to your clinician or pharmacist before starting anything new, especially if you take prescription medicines, are pregnant or breastfeeding.

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