Vitamin D does not work alone. The enzymes that turn it into its active forms need magnesium, and zinc and boron play supporting roles too. These are often called vitamin D cofactors. This guide explains whether you can take vitamin D and magnesium together, what each cofactor does, how much is enough, and when to take them.
It is educational, not medical advice.
Key Takeaways
- Yes, you can take vitamin D and magnesium together, at the same meal, morning or evening.
- Magnesium is needed to process vitamin D. The enzymes that convert vitamin D in the liver and kidneys appear to need magnesium as a cofactor.
- In a randomized trial, magnesium nudged vitamin D toward the middle: it raised levels in people starting near 30 ng/mL and lowered them in people starting higher.
- Zinc and boron support how the body uses vitamin D; low boron intake has been linked to lower vitamin D levels.
- Stay within the limits: 350 mg a day of supplemental magnesium, 40 mg of zinc and 20 mg of boron for adults.
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Can You Take Vitamin D and Magnesium Together?
Yes. There is no known problem with taking them at the same time, and many people take them at the same meal. They also work on the same pathway: vitamin D helps you absorb calcium, and magnesium helps the body process vitamin D.
- Same meal is fine. Take vitamin D with food that has some fat, since fat improves its absorption (NIH ODS: Vitamin D). Magnesium can go with the same meal.
- Morning or night both work. There is no strong evidence that one time is better for vitamin D, so pick one you will keep. Many people like magnesium in the evening.
- Split them if it suits you. Vitamin D in the morning and magnesium at night is also fine; what matters is taking both daily.
Not sure which form of vitamin D is in your supplement? Our guide to vitamin D vs D3 explains the difference between D3 and D2.
Why Magnesium Matters for Vitamin D
After you make or swallow vitamin D, the liver and kidneys convert it into 25(OH)D and then into the active form. A review of the research notes that all of the enzymes that metabolize vitamin D seem to require magnesium as a cofactor, so getting the recommended amount of magnesium helps you get the full benefit of vitamin D (Uwitonze and Razzaque, 2018). Magnesium also affects the levels of parathyroid hormone and the active form of vitamin D (NIH ODS: Magnesium).
A randomized, double-blind trial tested this directly. In 180 adults aged 40 to 85, with magnesium doses tailored to each person’s diet, magnesium raised blood 25(OH)D3 in people who started close to 30 ng/mL and lowered it in people who started higher, between about 30 and 50 ng/mL. The authors concluded that good magnesium status may be important for optimizing vitamin D status (Dai et al., 2018).
Which magnesium is best with vitamin D?
Forms that dissolve well, such as citrate, chloride, lactate and aspartate, are absorbed more completely than magnesium oxide (NIH ODS: Magnesium). Glycinate and bisglycinate are chelated forms, bound to the amino acid glycine, and are popular because they tend to be gentle on the stomach. Whichever form you choose, check the label for the milligrams of elemental magnesium per serving. To compare forms, see magnesium bisglycinate vs glycinate and magnesium glycinate vs citrate.
Prefer food first? See our list of foods high in magnesium, with milligrams per serving.
Zinc and Boron: The Other Vitamin D Cofactors
- Zinc. Adults need 8 mg a day (women) to 11 mg (men), with an upper limit of 40 mg (NIH ODS: Zinc).
- Boron. A trace mineral found in prunes, avocados, raisins, beans, apples and potatoes. In studies, low boron intake lowered blood 25(OH)D and raised the amount of calcium and magnesium lost in urine (NIH ODS: Boron). There is no official daily requirement; typical intake is about 1 to 1.5 mg a day and the upper limit is 20 mg (NIH ODS: Boron).
For the full picture on boron, including food sources and what studies found for bones and hormones, see boron benefits: vitamin D, hormones, dosage and food sources.
If you are choosing a zinc supplement, our guide to zinc picolinate vs bisglycinate vs gluconate compares how well each form is absorbed.
Whether magnesium and zinc can be taken at the same time is covered in magnesium and zinc together.
For the full list of nutrients that work alongside vitamin D, and how to time them, see our guide to vitamin D cofactors. For taking magnesium, zinc and boron together, see our guide to magnesium, zinc and boron.
How Much of Each Do You Need?
|
Nutrient |
Adult daily need |
Upper limit |
|---|---|---|
|
Vitamin D |
600 IU (to age 70); 800 IU (over 70) |
4,000 IU from all sources |
|
Magnesium |
310 to 320 mg (women); 400 to 420 mg (men), from food and supplements |
350 mg from supplements |
|
Zinc |
8 mg (women); 11 mg (men) |
40 mg from all sources |
|
Boron |
No official amount; typical intake 1 to 1.5 mg |
20 mg |
Sources: NIH ODS: Vitamin D, NIH ODS: Magnesium, NIH ODS: Zinc and NIH ODS: Boron. The magnesium limit applies only to supplements and medicines, not to food.
Vitamin D, K2 and Magnesium Together
Vitamin K2 is the other common partner. Vitamin D prompts the body to make calcium-binding proteins, and K2 switches them on. A daily routine of vitamin D3 with K2, plus magnesium from food or a supplement, covers the main parts of the pathway. For the details on K2, see vitamin D3 and K2: benefits, how much to take and when, and for vitamin D basics, see our vitamin D3 supplement guide. If you are comparing K2 forms, see vitamin K2: MK-4 vs MK-7.
Coming soon from Synchronicity: our Vitamin D Cofactor Capsules give magnesium 100 mg, zinc 10 mg and boron 3 mg per 2 capsules, made to pair with our Vitamin D3 + K2 Drops. Join the waitlist on the product page to hear when they launch; no payment is taken. Calcium completes the picture; see vitamin D and calcium, and for timing, the best time to take vitamin D. If you add fish oil, see vitamin D3, K2 and omega-3 together; if you also take ashwagandha, see ashwagandha and magnesium.
Safety and Who Should Check First
- Magnesium: too much from supplements often causes diarrhea, nausea and cramping. People with kidney problems should not take magnesium supplements without their clinician (NIH ODS: Magnesium).
- Zinc: 50 mg or more a day for weeks can lower copper levels. Zinc can also reduce the absorption of some antibiotics, so space them apart (NIH ODS: Zinc).
- Very high zinc and magnesium: very high zinc intake (142 mg a day in one study) interfered with magnesium absorption (NIH ODS: Magnesium). Normal amounts do not.
- Vitamin D: stay within 4,000 IU a day unless your clinician is monitoring you, and ask first if you take steroids, orlistat, some cholesterol medicines or thiazide diuretics (NIH ODS: Vitamin D).
Featured in this article
Vitamin D Cofactor CapsulesMagnesium 100 mg, zinc 10 mg and boron 3 mg per 2 capsules, all as glycinates, made to pair with vitamin D3.
Join the WaitlistComing soon. Third-party tested ingredients.
Sources
- NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. Updated 2025. ODS
- Uwitonze AM et al. Role of Magnesium in Vitamin D Activation and Function. The Journal of the American Osteopathic Association, 2018. De Gruyter
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. Updated 2026. ODS
- Dai Q et al. Magnesium status and supplementation influence vitamin D status and metabolism: results from a randomized trial. The American Journal of Clinical Nutrition, 2018. DOI
- NIH Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals. Updated 2026. ODS
- NIH Office of Dietary Supplements. Boron: Fact Sheet for Health Professionals. Updated 2022. ODS
Frequently Asked Questions
Can you take vitamin D and magnesium together?
Yes. Many people take them at the same meal, and they work on the same pathway: the enzymes that process vitamin D appear to need magnesium.
Can I take vitamin D and magnesium at night?
Yes. There is no strong evidence that one time of day is better for vitamin D. Take it with food that has some fat, and choose a time you will keep.
Does magnesium help vitamin D absorption?
Magnesium helps the body process vitamin D after it is absorbed. In a randomized trial, magnesium raised vitamin D levels in people who started near 30 ng/mL and lowered them in people who started higher.
Which magnesium is best for vitamin D?
Well-absorbed forms such as citrate and chelated forms such as glycinate or bisglycinate are common choices. Check the milligrams of elemental magnesium per serving.
What are vitamin D cofactors?
Nutrients the body needs to use vitamin D well. The main ones are magnesium, vitamin K2, zinc and boron.
Should I take zinc and boron with vitamin D?
Both support how the body uses vitamin D. Stay within the upper limits of 40 mg of zinc and 20 mg of boron a day, and remember food provides some of each.
These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.
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