A randomized, double-blind trial published February 2026 in Frontiers in Nutrition tested oral magnesium in 71 older adults with prediabetes and low blood magnesium (65 completed the study).
Over 16 weeks, those taking 360 mg of magnesium daily saw fasting glucose fall by about 0.5 mmol/L more than the placebo group. That is a real shift in a group already sitting on the edge of type 2 diabetes.
Prediabetes means blood sugar is higher than normal but not yet in the diabetic range. About 115 million US adults have prediabetes, according to the CDC's National Diabetes Statistics Report, and more than half of adults 65 and older meet the criteria.
Low blood magnesium, called hypomagnesemia, often runs alongside insulin resistance. When cells respond less effectively to insulin, the kidneys excrete more magnesium, which can drive levels down further and worsen blood sugar control.
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What the trial actually found
The Chinese team randomized 71 adults with a mean age of about 69 whose plasma magnesium sat at or below 0.80 mmol/L. Participants took one 360 mg magnesium oxide tablet with a meal each day for four months; 65 finished the trial.
Fasting plasma glucose fell by 0.497 mmol/L more in the magnesium arm than in placebo (p = 0.003). But HbA1c, insulin and HOMA-IR, standard markers of longer-term glucose control and insulin resistance, did not budge enough to reach statistical significance.
The authors concluded that correcting the deficiency lowered fasting glucose without shifting the broader glycemic picture. Coverage of the trial noted that the small effect size limits its clinical relevance over the long term, and that the benefit was tied to people who were magnesium-deficient to begin with.
Who is most at risk
Older adults absorb less magnesium and lose more through the kidneys with age. People with type 2 diabetes, heavy alcohol use, or absorption problems face similar risks, per the Harvard T.H. Chan School of Public Health's Nutrition Source.
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Some everyday prescriptions can also quietly deplete magnesium. Proton pump inhibitors such as omeprazole, taken for reflux, along with several diuretics and some antibiotics, are known to lower magnesium over time.
What to eat, and when to ask your doctor
The Recommended Dietary Allowance is 400 to 420 mg per day for men and 310 to 320 mg for women.
Reliable food sources include cooked spinach and Swiss chard, pumpkin seeds, almonds and cashews, black and kidney beans, and dark chocolate at 70 percent cocoa or higher.
A separate 12-month randomized trial in adults with type 2 diabetes, published July 2026 in Frontiers in Endocrinology, followed a similar pattern. Overall HbA1c did not fall significantly, but more people in the magnesium group reached the below-7 percent target, and the effect was stronger among those with low magnesium at the start.
Also read: Most people with prediabetes may be able to reverse it: what the evidence shows
None of this replaces medical care. Anyone with a prediabetes diagnosis, unexplained muscle cramps or fatigue, or a long-term PPI prescription should raise magnesium testing with their doctor before adding a supplement.
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