Can You Take Magnesium and Vitamin D Together?
Not medical advice — this summarizes published research; talk to a clinician before starting a supplement. Methodology.
Many people take them together. Magnesium is a cofactor for enzymes involved in vitamin D metabolism (PMID 29480918), and one review discusses how large vitamin D amounts might affect magnesium (PMID 28471760). In one 12-week trial, blood vitamin D levels differed between a group taking magnesium alongside vitamin D and a vitamin-D-only group. Ask your clinician before starting either.
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Quick answer: Many people take them together. Magnesium is a cofactor for enzymes involved in vitamin D metabolism, and how the two affect each other has been studied in only a few trials. There's no need to swallow them at the same moment. Ask your clinician before starting either.
How they work together
Vitamin D from a pill or from sunlight is inactive. It has to be converted twice — once in the liver (by 25-hydroxylase) and once in the kidney (by 1α-hydroxylase) — before it becomes calcitriol, the active hormone. Those converting enzymes depend on magnesium as a cofactor (PMID 29480918). Magnesium also helps regulate parathyroid hormone and the transport proteins that carry vitamin D in the blood. In practical terms, magnesium is one of several factors involved in vitamin D metabolism.
Magnesium status and vitamin D use
The relationship may run both ways. Using vitamin D involves magnesium, and one review discusses how large vitamin D amounts might affect magnesium status (PMID 28471760). The evidence is limited; talk to your clinician if you take large amounts of vitamin D.
What the trial actually showed
In a 12-week randomized controlled trial in overweight and obese adults, one group took vitamin D alone and another took vitamin D plus magnesium. The combined group's blood vitamin D level ended higher than the vitamin-D-only group (PMID 35576873). The trial used magnesium glycinate (360 mg, three times daily) alongside vitamin D (1,000 IU, three times daily). It was a single trial in one population, so it is not the last word.
The relationship is not simple
It's not a flat "more magnesium equals more vitamin D." A larger trial found magnesium's effect on vitamin D depended on the starting level (PMID 30541089), so results may differ from person to person. Ask your clinician.
How to dose them
| Nutrient | RDA (adults) | Upper limit |
|---|---|---|
| Magnesium | 310–320 mg (women) · 400–420 mg (men) | 350 mg/day from supplements |
| Vitamin D | 600 IU (ages 1–70) · 800 IU (over 70) | 4,000 IU/day for most adults |
- Magnesium: RDA 310–320 mg/day for women, 400–420 mg/day for men. The tolerable upper limit for supplemental magnesium is 350 mg/day — above that, loose stools are common (magnesium from food has no such limit).
- Vitamin D: RDA 600 IU/day (ages 1–70) or 800 IU/day (over 70). The upper limit is 4,000 IU/day for most adults; sustained higher doses need monitoring for hypercalcemia.
- Form: magnesium glycinate is well absorbed; vitamin D3 (cholecalciferol) is the form most products use.
- Timing: anytime that's consistent. Because vitamin D is fat-soluble, taking it with a meal that contains some fat modestly helps absorption. There's no proven benefit to taking magnesium and vitamin D at the exact same minute — daily adequacy is what counts.
Who should be careful
Two cautions. Anyone with kidney disease should not add magnesium supplements without medical supervision — impaired kidneys clear magnesium poorly, so it can build up. And vitamin D above the 4,000 IU/day upper limit should be monitored by a clinician. If you're on either at high doses, that's a conversation with your clinician, not a self-managed stack.
Frequently asked questions
Can you take magnesium and vitamin D together?
Many people do. Magnesium is a required cofactor for enzymes involved in vitamin D metabolism, and research on how the two affect each other is limited. There is no evidence they must be taken at the exact same time. Ask your clinician before starting either.
Does vitamin D affect magnesium?
Using vitamin D involves magnesium, and one review discussed how large vitamin D amounts might affect magnesium status. The evidence is limited; ask your clinician.
How much magnesium and vitamin D are recommended?
The adult magnesium RDA is 310–420 mg/day and the vitamin D RDA is 600–800 IU/day depending on age. Supplemental magnesium has a 350 mg/day upper limit (above which diarrhea is common); vitamin D has a 4,000 IU/day upper limit for most adults.
Do they need to be taken at the same time?
No. No study shows that taking them at the same moment works better than at different times of day.
Which magnesium form has been used with vitamin D?
One combined trial used magnesium glycinate, a well-absorbed form that is often described as gentle on the stomach. Vitamin D3 (cholecalciferol) is the form most products use.
Related guides
- Magnesium Dosage Guide · Best Time to Take Magnesium · Magnesium Forms Compared
- Vitamin D Dosage Guide · Vitamin D with K2
Sources
- Uwitonze AM, Razzaque MS. Role of Magnesium in Vitamin D Activation and Function. J Am Osteopath Assoc. 2018;118(3):181-189. PMID: 29480918
- Reddy P, Edwards LR. Magnesium Supplementation in Vitamin D Deficiency. Am J Ther. 2019;26(1):e124-e132. PMID: 28471760
- Cheung MM, et al. The effect of combined magnesium and vitamin D supplementation on vitamin D status. Nutrition. 2022;99-100:111674. PMID: 35576873
- Dai Q, et al. Magnesium status and supplementation influence vitamin D status and metabolism: a randomized trial. Am J Clin Nutr. 2018;108(6):1249-1258. PMID: 30541089
- NIH Office of Dietary Supplements. Magnesium & Vitamin D Fact Sheets for Health Professionals. ods.od.nih.gov