Can You Take Magnesium and Vitamin D Together?
Not medical advice — this summarizes published research; talk to a clinician before starting a supplement. Methodology.
Yes — and taking them together may be necessary, not just safe. Magnesium is a cofactor the enzymes that convert vitamin D into its active form depend on (PMID 29480918), and high-dose vitamin D can deplete magnesium (PMID 28471760). In a 12-week trial, the group taking magnesium alongside vitamin D finished with higher vitamin D levels than the vitamin-D-only group.
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Quick answer: Take them together. Magnesium doesn't just coexist with vitamin D — your body cannot activate vitamin D without it. If you supplement vitamin D but run low on magnesium, some of that vitamin D never becomes usable, and the high dose can pull your magnesium down further. There's no need to swallow them at the same moment; what matters is that both are adequate every day. Magnesium glycinate paired with vitamin D3 is the cleanest combination.
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: low magnesium is a bottleneck that can blunt the vitamin D you're taking.
The depletion risk most pages skip
The relationship runs both ways. Because activating and using vitamin D consumes magnesium, taking large doses of vitamin D on its own can worsen an existing magnesium shortfall (PMID 28471760). This is the part most "can you take them together" articles leave out: if you're on a high-dose vitamin D regimen with no attention to magnesium, you may be quietly running your magnesium down — which then limits the vitamin D. Pairing them closes that loop.
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 vitamin D level rose about 6.3 ng/mL over the study and finished 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) — which is why glycinate is the form we point to. It was a single trial in one population, so treat it as supportive rather than the last word.
The nuance the listicles miss
It's not a flat "more magnesium equals more vitamin D." A larger trial found magnesium's effect on vitamin D is dependent on your starting level: when baseline vitamin D is low, magnesium supplementation raises it — but at higher baseline levels the effect can flip (PMID 30541089). Translation: this pairing is most valuable when you're actually low or deficient, which is when people are usually supplementing anyway. It's a corrective relationship, not a "megadose both and stack the benefits" one.
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 for gentleness and absorption; vitamin D3 (cholecalciferol) over D2.
- 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 4,000 IU/day without bloodwork risks hypercalcemia (dangerously high blood calcium) over time. 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?
Yes, and for many people it is beneficial to. Magnesium is a required cofactor for the enzymes that convert vitamin D into its active form, so adequate magnesium helps vitamin D work. High-dose vitamin D can also deplete magnesium, so pairing them helps prevent a shortfall. There is no evidence they must be taken at the exact same time.
Does vitamin D deplete magnesium?
It can. Activating and using vitamin D consumes magnesium, so taking large doses of vitamin D without enough magnesium can worsen a magnesium deficit — one reason magnesium status is worth addressing alongside vitamin D therapy.
How much magnesium and vitamin D should I take?
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. The benefit is about overall daily adequacy of both nutrients, not minute-to-minute timing. No study shows that taking them at the same moment works better than at different times of day.
Which magnesium form is best with vitamin D?
Magnesium glycinate is a good default — well absorbed, gentle on the stomach, and the form used in the strongest combined trial. Pair it with vitamin D3 (cholecalciferol) rather than D2.
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