Zinc and magnesium, vitamin D, calcium, potassium, iron and B6: how to combine them

Key points

• Vitamin D and magnesium: a good pair. Magnesium is needed to process vitamin D, and in one study, vitamin D levels rose most when both were taken together.
• Calcium and zinc: no problem together with magnesium in usual amounts.
• Potassium: a good match, because the body needs magnesium to hold on to potassium.
• Vitamin B6: in a study with highly stressed adults, magnesium plus B6 helped more than magnesium alone.
• Iron: better taken at a different time, ideally with a glass of orange juice rather than milk.

Contents

1. All combinations at a glance
2. Magnesium and vitamin D
3. Magnesium and calcium
4. Magnesium and zinc
5. Magnesium and potassium
6. Magnesium and iron
7. Magnesium and vitamin B6
8. Magnesium and tryptophan
9. Vitamin C, B12, omega-3 and selenium
10. What should you not take with magnesium?
11. Your combination plan for the day
12. Frequently asked questions
13. Limits of the research and all sources

All combinations at a glance

Combination	Take together?	Gap needed?	Evidence
Magnesium + vitamin D	yes	no	promising
Magnesium + calcium	yes	no	solid
Magnesium + zinc	yes	no, at usual amounts	mixed
Magnesium + potassium	yes	no	solid
Magnesium + iron	better separate	about 2 hours	limited
Magnesium + vitamin B6	yes	no	promising
Magnesium + tryptophan	yes	no	positive

"Evidence" describes how well the combination itself has been studied, not the individual nutrient. The details are in the sections and in the source table at the end.

Can you take vitamin D and magnesium together?

Yes, and the two complement each other. It's best to take them together with a meal that contains some fat, for example at breakfast with yoghurt or egg. You don't need to leave a gap.

The reason they pair well: magnesium is needed to form, transport and activate vitamin D.¹ If you take a lot of vitamin D, it's worth paying attention to your magnesium supply too.

What the studies show: In a controlled study with 180 adults aged 40 to 85, participants received magnesium or a placebo for twelve weeks. When the starting vitamin D level was on the low side, it rose with magnesium. When it was already high, it fell. The researchers conclude that a good magnesium supply may be important for an optimal vitamin D level.² A second study followed 95 overweight adults. Vitamin D levels rose most in the group taking 1,000 IU of vitamin D3 plus 360 mg of magnesium as glycinate, by an average of 6.3 ng/ml.³

Conversely, vitamin D has little effect on magnesium absorption: across 47 balance studies, it rose only slightly.⁴ So you don't absorb magnesium better because of the vitamin D; rather, vitamin D benefits from a good magnesium supply.

For both nutrients, there are officially approved EU claims that fit well together here:

• Vitamin D contributes to normal absorption/utilisation of calcium and phosphorus.
• Vitamin D contributes to the maintenance of normal bones.
• Magnesium contributes to the maintenance of normal bones.
• Vitamin D contributes to the maintenance of normal muscle function.
• Magnesium contributes to normal muscle function.

There's no separate formula for how much magnesium makes sense alongside vitamin D. Your normal daily requirement applies, and from supplements at most 250 mg of magnesium a day.⁶ For vitamin D, the upper limit for adults is 100 µg (4,000 IU) a day.⁶ How much magnesium you need is covered in How much magnesium per day?

Vitamin D3, K2 and magnesium together

Many supplements combine vitamin D3 with vitamin K2. These can also be taken together with magnesium, again with a meal containing some fat. We're not aware of any studies showing that they interfere with each other's absorption.

Can you take calcium and magnesium together?

Yes. Calcium and magnesium can be taken with the same meal, no gap needed. The worry that calcium blocks magnesium absorption isn't backed up by measurements in the gut: calcium has little effect on it.⁸

What matters more is the ratio over the whole day. Experts suggest getting about twice as much calcium as magnesium, so a ratio of roughly 2 to 1.^{1, 9} In Western countries it's often higher than that, because a lot of calcium comes from dairy and relatively little magnesium.⁹

What the studies show: An analysis of US dietary data found an average ratio of over 3 to 1 since the year 2000. The authors suggest a range of 1.7 to 2.6 and see high calcium intake as a reason to pay attention to magnesium.⁹

For both minerals, there are officially approved claims:

• Calcium is needed for the maintenance of normal bones.
• Magnesium contributes to the maintenance of normal bones.
• Calcium contributes to normal muscle function.

Can you take zinc and magnesium together?

Yes. In the amounts found in typical supplements, you can take zinc and magnesium together, for example both with your evening meal. You don't need a gap.

Only very high amounts of zinc slow magnesium down: in one study, 142 mg of zinc a day lowered both the absorption and the balance of magnesium.¹¹ That's more than five times the amount considered a safe upper limit. For adults, that limit is 25 mg of zinc a day from all sources.⁶

What the studies show: In an Italian care home, 43 older people with sleep problems took an evening blend for eight weeks. It contained 5 mg of melatonin, 225 mg of magnesium and 11.25 mg of zinc. The participants slept clearly better afterwards than with a placebo.¹² In 16 young athletes who slept only four hours for two nights, a zinc-magnesium combination made no difference.¹³ What the combination delivers therefore depends a lot on who takes it and why.

For zinc, these claims are among those officially approved:

• Zinc contributes to the normal function of the immune system.
• Zinc contributes to the maintenance of normal bones.
• Zinc contributes to normal protein synthesis.
• Magnesium contributes to normal protein synthesis.

Can you take potassium and magnesium together?

Yes, the two even belong together. Magnesium and potassium are the most important minerals inside your cells, and the body needs magnesium to hold on to potassium. You can take them together with a meal.

What the studies show: Without enough magnesium, the kidneys lose more potassium, and a low potassium level is then hard to correct with potassium alone.¹⁴ That's why doctors often check magnesium too when potassium is low. In a study with 300 women who had a low dietary intake of potassium, calcium and magnesium, potassium lowered blood pressure slightly. Adding magnesium didn't strengthen the effect.¹⁵

Officially approved for both:

• Potassium contributes to normal muscle function.
• Magnesium contributes to normal muscle function.
• Potassium contributes to normal functioning of the nervous system.
• Magnesium contributes to normal functioning of the nervous system.
• Potassium contributes to the maintenance of normal blood pressure.
• Magnesium contributes to electrolyte balance.

For most people, fruit, vegetables, potatoes and pulses are the easiest way to get more potassium. Many of these foods provide magnesium at the same time.

Can you take iron and magnesium together?

Better not at the same time. Take iron with a different meal from magnesium, with a gap of about two hours. A tried-and-tested pattern: iron in the morning with a glass of orange juice, magnesium with your evening meal.

The background: magnesium compounds with an alkaline effect, of the kind also found in heartburn remedies, can bind iron in the gut. There's hardly any data on this for normal magnesium amounts from supplements. We recommend the gap out of caution, and it costs you nothing.

What the studies show: In a study with 13 men, magnesium hydroxide lowered iron absorption to about half.¹⁷ A similar study with 16 men found no difference.¹⁸ Both studies used very high amounts, similar to an iron overdose. As far back as 1969, magnesium trisilicate, a heartburn remedy, lowered iron absorption.¹⁹ Calcium is a much stronger brake: 165 mg of calcium from milk or cheese lowered iron absorption by 50 to 60%.¹⁰

For iron, these claims are among those officially approved:

• Iron contributes to normal oxygen transport in the body.
• Iron contributes to the reduction of tiredness and fatigue.
• Magnesium contributes to a reduction of tiredness and fatigue.

Magnesium with vitamin B6: what does the combination offer?

Magnesium and vitamin B6 can be taken together without any problem, at any time of day. The combination is widely sold as a "magnesium B6 complex", and there's a larger study that compared exactly these two substances.

What the studies show: 264 stressed adults with low blood magnesium levels took 300 mg of magnesium for eight weeks, either with 30 mg of vitamin B6 or without. In both groups, the stress score on the questionnaire dropped clearly, by around 45% and 42%. Among the 162 participants with high stress, it improved 24% more with B6 than with magnesium alone.²¹ B6 did not additionally raise the magnesium level in red blood cells.²² So the advantage wasn't down to better magnesium absorption.

For both, there are officially approved claims that fit together here:

• Vitamin B6 contributes to normal functioning of the nervous system.
• Magnesium contributes to normal functioning of the nervous system.
• Vitamin B6 contributes to normal psychological function.
• Magnesium contributes to normal psychological function.
• Vitamin B6 contributes to the reduction of tiredness and fatigue.

And magnesium with tryptophan?

That combines well too, ideally in the evening with your evening meal. Tryptophan is the building block for serotonin and melatonin, and magnesium contributes to normal functioning of the nervous system. If you take antidepressants, talk to your doctor before taking tryptophan. Everything on studies, dosage and safety is in our article L-tryptophan and magnesium

Vitamin C, B12, omega-3 and selenium: does that work too?

Yes. For vitamin C, vitamin B12, omega-3 fatty acids and selenium, we're not aware of any studies showing interference with magnesium. You can take them with the same meal. Like vitamin D, omega-3 capsules are best taken with a meal that contains some fat.

What shouldn't you take together with magnesium?

The list for nutrients is short: take iron separately, zinc is fine in usual amounts. More important are a few medicines that magnesium binds in the gut.

What	How to combine it
Iron	about 2 hours' gap, separate meal
Very high-dose zinc (well above 25 mg)	avoid, slows magnesium11
Thyroid hormone (levothyroxine)	take at different times, agree the gap with your GP or pharmacist
Antibiotics (tetracyclines, quinolones)	magnesium 4 hours before or 2 hours after
Osteoporosis drugs (bisphosphonates)	gap as stated on the patient leaflet

The details and studies on these medicines are in When should you take magnesium?

Your combination plan for the day

Here's how you can sensibly spread several supplements across your day:

Meal	What goes well together
Breakfast with some fat	Vitamin D (with or without K2), magnesium, omega-3, B vitamins
Separate meal, with vitamin C	Iron, without milk, coffee and calcium
Evening meal	Magnesium, zinc, calcium, tryptophan if wanted

If you take more than about 250 mg of magnesium a day, split it across two meals; that way, your body absorbs a larger share. We explain why in When should you take magnesium? What else helps absorption is covered in How does the body absorb magnesium?

Frequently asked questions

Can you take zinc and magnesium together? Yes. In usual amounts, the two don't interfere with each other. Only very high zinc intake, 142 mg a day in one study, slowed magnesium absorption.¹¹ Stick to at most 25 mg of zinc a day.⁶

Why shouldn't you take calcium and magnesium together? That's a common piece of advice that measurements don't support: calcium has little effect on magnesium absorption.⁸ What you should keep separate from iron, though, is calcium, because calcium slows iron absorption.¹⁰

Is it better not to take vitamin D and magnesium together? No, you can take them together. There's no reason for a gap. Magnesium is needed to process vitamin D, and in one study, vitamin D levels rose most when both were taken together.^{1, 3}

How much magnesium alongside vitamin D? There's no dedicated recommendation. Your normal daily requirement applies. In the study with vitamin D3, participants took 360 mg of magnesium a day,³ and the upper limit for magnesium from supplements is 250 mg.⁶ The rest ideally comes from food.

How much of a gap between iron and magnesium? About two hours. This is our recommendation out of caution, because alkaline magnesium compounds lowered iron absorption in studies.^{17, 19}

Magnesium with potassium: what does that do? Potassium and magnesium work closely together: without enough magnesium, the body holds on to potassium less well.¹⁴ Potassium contributes to the maintenance of normal blood pressure. With kidney disease and certain blood pressure medicines, please get medical advice first.¹⁶

Limits of the research and all sources

Studies that test exactly one two-way combination against the single nutrients and a placebo are rare. The vitamin D studies are medium-sized and ran for twelve weeks; the second one looked at people who were overweight. The B6 study had no placebo group and was blinded only for those analysing the data. It was funded by the supplement's manufacturer, and the benefit only showed up in the subgroup under heavy stress. For zinc and magnesium, the positive findings mostly come from combination products with melatonin; the short study with athletes found no effect. For blood pressure, magnesium added to potassium brought no further benefit in one study. For iron and magnesium at usual amounts, measurements are missing; the available studies worked with amounts like those seen in poisoning, or with heartburn remedies. The recommended calcium-to-magnesium ratio comes from observational data, not intervention studies.

Show all 22 studies and sources

#	Study	Who was studied	Result	Strength of evidence
1	Rosanoff et al. 2016, Adv Nutr	Review article	Magnesium needed to form and activate vitamin D; Ca:Mg around 2 to 1 favourable	Review
2	Dai et al. 2018, Am J Clin Nutr	180 adults, 40–85 years, magnesium dosed by diet, 12 weeks	Vitamin D level rose with a low starting value, fell with a high one	controlled study, publicly funded (NCI)
3	Cheung et al. 2022, Nutrition	95 overweight adults, 1,000 IU D3 ± 360 mg magnesium glycinate, 12 weeks	strongest vitamin D rise with the combination (+6.3 ng/ml)	controlled study, funded by the American Heart Association
4	Hodgkinson et al. 1979, Clin Sci	47 balance studies, patients	vitamin D: magnesium absorption slightly higher, balance unchanged	basic research study
5	Dawson-Hughes et al. 2015, J Acad Nutr Diet	50 older adults, single dose of vitamin D3	32% higher peak with fat	small randomised study
6	EFSA 2025: Summary of Upper Levels	Regulatory overview (version 11)	Upper limits for adults: magnesium from supplements 250 mg, zinc 25 mg, vitamin B6 12 mg, vitamin D 100 µg, calcium 2,500 mg	official assessment
7	Theuwissen et al. 2013, J Thromb Haemost	15 healthy people on a vitamin K antagonist, 10–45 µg K2	Clotting value changed from as little as 10 µg in some	small study
8	Brannan et al. 1976, J Clin Invest	Measurement in the small intestine	Calcium has little effect on magnesium absorption	basic research study
9	Costello et al. 2021, Adv Nutr	US dietary and supplement database data	Ca:Mg mostly above 3; 1.7–2.6 suggested	perspective article, NIH-funded
10	Hallberg et al. 1991, Am J Clin Nutr	126 adults	165 mg calcium lowered iron absorption by 50–60%	basic research study
11	Spencer et al. 1994, J Am Coll Nutr	Men, 142 mg zinc/day	very high zinc lowers magnesium absorption and balance	small
12	Rondanelli et al. 2011, J Am Geriatr Soc	43 care-home residents, 5 mg melatonin + 225 mg magnesium + 11.25 mg zinc, 8 weeks	Sleep quality clearly better than placebo	small controlled study, combination product
13	Gallagher et al. 2024, Nutrients	16 trained men, zinc-magnesium aspartate, 2 short nights	No effect on sleep and performance	small controlled study
14	Huang & Kuo 2007, J Am Soc Nephrol	Review article	Magnesium deficiency increases potassium loss via the kidneys	Review
15	Sacks et al. 1998, Hypertension	300 women with low intake, 16 weeks	Potassium lowered blood pressure slightly; magnesium added no extra effect	controlled study
16	Hunter & Bailey 2019, Nephrol Dial Transplant	Review article	Risk of too much potassium: kidney impairment, ACE inhibitors, ARBs, potassium-sparing diuretics	Review
17	Wallace et al. 1998, Acad Emerg Med	13 men, high iron dose + magnesium hydroxide	Iron absorption roughly halved	small study, poisoning model
18	Snyder et al. 1999, Ann Emerg Med	16 men, high iron dose + magnesium hydroxide	No difference	small study, poisoning model
19	Hall & Davis 1969, Med J Aust	People, iron + magnesium trisilicate	Iron absorption reduced	old study, heartburn remedy
20	Hurrell & Egli 2010, Am J Clin Nutr	Review article	Vitamin C promotes, calcium, polyphenols and phytate reduce iron absorption	Review
21	Pouteau et al. 2018, PLoS One	264 stressed adults with low magnesium levels, 300 mg Mg ± 30 mg B6, 8 weeks	Stress dropped clearly in both groups; with high stress, 24% more with B6	randomised, no placebo, funded by Sanofi
22	Noah et al. 2020, Magnes Res	Secondary analysis of no. 21	B6 did not additionally raise the magnesium level in red blood cells	secondary analysis, Sanofi

Author: PRONESIUM Editorial Team · Last reviewed: 29/09/2026 · This article does not replace medical advice.