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Head-to-head evidence comparison — which supplement is right for you?
Magnesium vs Vitamin D3: they're closely matched on evidence (8.5 vs 7.5/10); they work on different things and are often used together, not either/or. Take the 60-second quiz for a pick tailored to your goals.
Magnesium and Vitamin D3 are closely matched across evidence, studies, and safety.
Verdict
Probably helps
9 of 13 studies with measurable effects showed benefit.
Top outcomes
Verdict
Probably helps
12 of 21 studies with measurable effects showed benefit.
Top outcomes
200-350mg elemental magnesium daily
Evening for sleep/relaxation (glycinate), Morning for energy (malate), Anytime (citrate)
Depends on goal - see notes
2000-4000 IU daily
Morning with breakfast
D3 (cholecalciferol) softgel or liquid
and 4 more not shown
and 1 more not shown
Magnesium deficiency impairs vitamin D metabolism and effectiveness
TAKE TOGETHER. Magnesium essential for vitamin D activation.
1-2 weeks
1-2 weeks
1 week
Immediate
4-8 weeks
4-8 weeks
2-4 weeks
4-8 weeks
Magnesium supplementation in pregnancy
The Cochrane database of systematic reviews (2014) · Meta analysis · n=9090
Women receiving magnesium were significantly less likely to require hospitalisation during pregnancy (RR 0.65, 95% CI 0.48 to 0.86; three trials, 1158 women).Of the 10 trials included in the review, only two were judged to be of high quality overall.
Magnesium Supplementation and Blood Pressure: A Systematic Review and Meta-Analysis
Hypertension (2025) · Meta analysis · n=2709
38 RCTs with 2709 participants analyzed
Magnesium and Potassium Supplementation for Systolic Blood Pressure Reduction in the General Normotensive Population: A Systematic Review and Subgroup Meta-Analysis for Optimal Dosage and Treatment Length
Nutrients (2024) · Meta analysis
Both supplements demonstrated greater reductions in SBP for the general population at lower dosages and longer treatment durations.
Vitamin D supplementation vs. placebo and incident type 2 diabetes in an ancillary study of the randomized Vitamin D and Omega-3 Trial
Nature communications (2025) · Meta analysis · n=5205
Mean body mass index (BMI) was 27.5 kg/m2 (SD = 5.3), with 51% female and 17% Black race/ethnicity.
Vitamin D Supplementation for Patients with Dysmenorrhoea: A Meta-Analysis with Trial Sequential Analysis of Randomised Controlled Trials
Nutrients (2024) · Meta analysis · n=687
TSA revealed that the current RCTs provide sufficient information.
Vitamin D and respiratory tract infections
BMJ (2017) · Meta analysis · n=11321
12% reduction in respiratory infections overall
Based on meta-analysis of 38 RCTs with 2709 participants showing -7.68 mmHg reduction in hypertensive individuals. Effects are greatest in those with hypomagnesemia. Limited evidence in normotensive populations.
Meta-analysis showed 12% overall reduction in respiratory infections, with greater benefits in severely deficient individuals. Daily dosing more effective than bolus. Conservative estimate assumes most users not severely deficient.
AI-estimated from published studies. Interpret as directional guidance.
Both Magnesium and Vitamin D3 are closely matched — the best choice depends on your specific health goals.
For bone health, Vitamin D3 has a higher relevance score (92 vs 85).
Magnesium and Vitamin D3 may work well together: Magnesium deficiency impairs vitamin D metabolism and effectiveness TAKE TOGETHER. Magnesium essential for vitamin D activation.
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The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.