Oral magnesium supplements and insulin resistance in individuals with diabetes and pre-diabetes: an updated systematic review and meta-analysis of randomized controlled trials

BACKGROUND: Diabetes is a common health challenge. Previous studies have established that diabetes is often associated with low circulating magnesium status. As evidence from randomized controlled trials (RCTs) on the effect of magnesium supplementation on insulin resistance remains inconsistent, and the influence of baseline status is not fully understood, this systematic review and meta-analysis evaluated the effects of magnesium supplements, compared with placebo, on insulin resistance in individuals with diabetes and pre-diabetes. METHODS: A comprehensive search based on the PRISMA 2020 guidelines was conducted in PubMed, Web of Science, and Scopus until 24 April 2026. Randomized controlled trials with a population of individuals with diabetes and pre-diabetes that received any magnesium supplements compared to a placebo group, evaluating insulin and the HOMA-IR index as the primary outcome, were included in our study. Secondary outcomes were serum magnesium level, HbA1c, and fasting blood glucose (FBG). We pooled data using a random-effects model to estimate changes in outcomes. Subgroup analyses were conducted based on dosage (> 250 and ≤ 250 mg/day) and follow-up duration (under or over 12 weeks). Meta-regression, publication bias, and sensitivity analysis were performed as well. RESULTS: Fifteen RCTs involving 1,085 participants met the criteria. Overall, the oral magnesium supplementation did not result in a statistically significant change in insulin levels (MD = - 1.73; 95% CI: -3.73 to 0.27; p-value = 0.09) and HOMA-IR (MD = - 0.74; 95% CI: -1.58 to 0.09; p-value = 0.08) in people with diabetes. Similar non-significant findings were observed in individuals with prediabetes (p > 0.05). However, meta-regression analysis demonstrated that baseline insulin level and HOMA-IR index significantly modified the intervention effect (p = 0.01), suggesting differential responsiveness across patient subgroups. No significant associations were observed for baseline HbA1c, fasting blood glucose, magnesium levels, age, or BMI. Subgroup analysis based on doses and duration of follow-up did not change the significance of the result. CONCLUSION: Magnesium supplementation does not appear to improve insulin resistance in individuals with diabetes or prediabetes significantly. However, its effects may depend on baseline insulin status, highlighting the need for targeted interventions in individuals with higher insulin resistance. Future well-designed trials with larger sample sizes are needed to clarify baseline insulin effects.