Should you take vitamin D and magnesium together?
Most people only need the vitamin D. Food usually covers magnesium. Magnesium seems to help your body use vitamin D. But in one trial it lowered vitamin D in people who started higher.
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Do I need vitamin D and magnesium supplements?
Most people need only the vitamin D, and only for part of the year. Between October and early March, we do not make enough vitamin D from sunlight.
So the NHS says everyone should consider 10 micrograms (400 IU) a day in autumn and winter. Magnesium is different. The NHS says a varied, balanced diet should give you all the magnesium you need.
| Vitamin D | Magnesium | |
|---|---|---|
| Who the NHS says should consider a supplement | Everyone in autumn and winter. Some people all year. | Not suggested for everyone. A varied diet should cover it. |
| How much adults need a day | 10 micrograms (400 IU). | 300mg for men and 270mg for women aged 19 to 64. |
| Limit from supplements | No more than 100 micrograms (4,000 IU) a day. | 400mg or less a day is unlikely to cause any harm. |
Sources: NHS: vitamin D; NHS: other minerals
Take 10 micrograms all year if you’re not often outdoors, live in a care home or usually cover most of your skin outside. With dark skin, for example an African, African-Caribbean or south Asian background, the NHS says consider it all year.
Start with a 10 microgram vitamin D this winter. Before you add magnesium, look at your plate: spinach, nuts and wholemeal bread all contain it.
Does magnesium help vitamin D work?
It seems to play a part. The vitamin D in a tablet isn’t ready to use. Your liver and kidneys turn it into an active form called calcitriol.
Each step uses enzymes, which are proteins that help the body carry out chemical reactions. A 2018 review says all the enzymes that handle vitamin D seem to need magnesium as a helper.
How your body turns vitamin D into a form it can use
- 1
Vitamin D in
From sunlight on your skin, food or a tablet.
- 2
Liver
Changes it first. Magnesium seems to help with this step.
- 3
Kidneys
Make the active form, calcitriol. Magnesium seems to help here too.
- 4
Bones
Calcitriol helps control the calcium and phosphate in your body, which keep bones healthy.
Sources: NHS: vitamin D; NHS: colecalciferol; Uwitonze and Razzaque 2018
Survey data from the US found people who had more magnesium were less likely to be low in vitamin D. The authors called this preliminary. A survey shows a link, not that one causes the other.
So magnesium matters, but that is a reason to eat enough of it, not proof you need a tablet. Wondering if you run low? See signs of low magnesium.
Can magnesium raise your vitamin D level?
Sometimes, and it can lower it too. In a US trial, 180 adults aged 40 to 85 took magnesium or a dummy pill for 12 weeks. Each dose was set from what that person already ate.
| Vitamin D level at the start | What magnesium did |
|---|---|
| Close to 30 ng/mL (about 75 nmol/L) | Raised it. |
| Higher, from about 30 to 50 ng/mL (about 75 to 125 nmol/L) | Lowered it. |
Source: Dai and others 2018
Magnesium didn’t just push vitamin D up. The authors say good magnesium status may be important for getting vitamin D levels right.
It was one trial of 180 people, most with a history of polyps, which are small growths in the bowel. Almost everyone was white, and all ate a lot of calcium compared with magnesium. It didn’t test vitamin D tablets.
Want to know where you start? See vitamin D blood test results and the magnesium blood test. If your result is in ng/mL, multiply by about 2.5 to get nmol/L.
Can you take vitamin D and magnesium at the same time?
The NHS sets a limit for each one. Stay under both, and count every product you take. For prescribed vitamin D, the NHS says take tablets with your main meal of the day.
We found no NHS advice on the best time to take magnesium, or on spacing the two apart.
Before you take vitamin D and magnesium together
- In autumn and winter, consider 10 micrograms (400 IU) of vitamin D a day, or all year if the NHS advises that for you. Your doctor may advise a different amount.
- Take no more than 100 micrograms (4,000 IU) of vitamin D a day, across all products.
- Keep magnesium from supplements to 400mg a day or less, unless a doctor advises otherwise.
- Add in any multivitamin that also contains vitamin D or magnesium.
- Taking prescribed vitamin D? Take the tablets with your main meal of the day.
- On a prescribed medicine? Check with a pharmacist first.
Sources: NHS: vitamin D; NHS: other minerals; NHS: colecalciferol
More than 400mg of magnesium for a short time can cause diarrhoea. Too much vitamin D over a long time can build up calcium, which can weaken the bones and damage the kidneys and the heart.
Choosing a magnesium? See which magnesium to take.
Worried about your dose? Read can you take too much vitamin D.
Who should check with a doctor first?
Tell your doctor before you start vitamin D if you have kidney problems or have had kidney stones. The same goes if you have high calcium in your blood or pee.
Or if you have sarcoidosis, a rare condition where small lumps of swollen tissue form in the body. Or if you have a peanut or soya allergy, high vitamin D in your blood, or have ever reacted to a vitamin D product.
Some medicines matter too. The NHS lists these for colecalciferol, the form most vitamin D you can buy comes in, alongside ergocalciferol.
| Medicine | What the NHS says |
|---|---|
| Digoxin, for heart problems | With vitamin D you may get too much calcium in your blood. This may cause an abnormal heartbeat. |
| Some water tablets, such as bendroflumethiazide or indapamide | With vitamin D you may get too much calcium in your blood. |
| Epilepsy medicines, such as phenytoin or carbamazepine | You may need a larger dose of vitamin D. |
| Steroids, such as prednisolone or hydrocortisone | These may reduce the effects of vitamin D. |
| Alendronic acid, a bone medicine | Tell your doctor about supplements with magnesium. Wait at least 30 minutes after it before another medicine by mouth. |
Sources: NHS: colecalciferol and other medicines; NHS: alendronic acid
Already on prescribed vitamin D? The NHS says don’t take other supplements with calcium or vitamin D without talking to your doctor first.
Never stop or change a prescribed medicine without your prescriber.
When to speak to a GP
Speak to a GP or pharmacist if:
- You want vitamin D but have kidney problems, past kidney stones, high calcium or vitamin D, sarcoidosis, or a peanut or soya allergy.
- You take digoxin, a water tablet, an epilepsy medicine, a steroid or alendronic acid.
- Your doctor prescribed vitamin D and you want to add another supplement with calcium or vitamin D.
- Bone, muscle or joint pain lasts longer than a few weeks or months on vitamin D. Your doctor may test your vitamin D level.
On vitamin D and you’re sick, feel confused, or get bone or joint pain or an irregular heartbeat? These could be signs of too much calcium. Call your doctor or 111.
Call your doctor or 111 too if you need to pee more often or get swelling anywhere. The same goes for a high temperature with a sharp pain in your side or one side of your lower back.
Call 999 for signs of a serious allergic reaction. These include lips, mouth, throat or tongue that suddenly swell. Or breathing very fast, struggling to breathe, a tight throat or struggling to swallow.
Call 999 too if skin, tongue or lips turn blue, grey or pale, or you suddenly feel very confused, drowsy or dizzy. The same goes if someone faints and can’t be woken.
Still low after months of tablets? See low vitamin D despite supplements.