How much vitamin D should I take?
10 micrograms (400 IU) a day is enough for most adults. But shop tablets often say 1,000, 4,000 or 10,000 IU. One quick sum shows which ones go too far.
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How much vitamin D should I take a day?
For most adults, 10 micrograms a day. That’s 400 IU. The NHS says adults need 10 micrograms a day, and that this is enough for most people.
The same amount applies if you’re pregnant, breastfeeding or at risk of low vitamin D.
The ceiling is 100 micrograms (4,000 IU) a day. The NHS says don’t take more than that, as it could be harmful.
Too much over a long time can cause calcium to build up in your body. That can weaken bones and damage the kidneys and heart.
- Below 400 IU a dayLess than the NHS 10 micrograms.
- 400 up to 4000 IU a dayEnough for most, up to the NHS maximum.
- Above 4000 IU a dayAbove the NHS daily maximum.
Source: NHS
Some medical conditions mean you may not be able to safely take as much. If your doctor gave you a different dose, follow their advice.
How many IU is 10 micrograms?
400 IU. Labels use two units, and the NHS says 1 microgram equals 40 IU.
So that quick sum is this: divide the IU by 40 to get micrograms. A 1,000 IU tablet is 25 micrograms. A 4,000 IU tablet is 100 micrograms, the whole daily limit in one go.
| On the label | Micrograms | What it means |
|---|---|---|
| 400 IU | 10 | The NHS daily amount for adults. |
| 1,000 IU | 25 | A suitable daily dose, says one NHS guideline. |
| 2,000 IU | 50 | Top of the daily dose a doctor may prescribe after a course. |
| 4,000 IU | 100 | The NHS daily maximum for adults. |
| 5,000 IU | 125 | Above the NHS daily maximum. |
| 10,000 IU | 250 | Two and a half times the daily maximum. |
| 50,000 IU | 1,250 | A weekly dose a doctor may prescribe for a short course. |
Sources: NHS; NHS colecalciferol; Nottinghamshire APC
Only finding 1,000 IU in the shop? An NHS guideline from Nottinghamshire says these are considerably cheaper than 400 IU tablets. It calls 1,000 IU a suitable daily dose to prevent low vitamin D.
Taking more than one product? Check each label and add the vitamin D together.
When should I take vitamin D, and who needs it all year?
The NHS says everyone should consider a daily 10 microgram supplement from October to early March.
From about late March or early April to the end of September, most people should be able to make enough from the sun. You may choose to stop then.
The NHS says to take, or consider, 10 micrograms every day all year if you:
- are not often outdoors, for example you’re frail or housebound
- live in a care home
- usually wear clothes that cover most of your skin when outdoors
- have dark skin, for example an African, African-Caribbean or south Asian background
Taking a capsule or tablet? The NHS says to take it with your main meal of the day.
Wondering if one weekly dose works as well? See vitamin D daily or weekly.
Is a higher vitamin D dose better?
Not for bones, in a 3-year trial of 311 healthy adults aged 55 to 70. They took 400, 4,000 or 10,000 IU a day.
Bone density in the forearm came out lower on 4,000 and 10,000 IU than on 400 IU. Bone strength did not differ.
The authors said the results do not support a bone benefit from high doses. Whether high doses are harmful needs more research.
Numbers like 40,000 or 50,000 IU are different. They’re loading doses: a short, strong course a doctor prescribes to raise a low level quickly.
How a prescribed vitamin D course usually goes
- 1
Blood test
Shows a very low vitamin D level.
- 2
Loading dose
For example, 50,000 IU once a week for 6 weeks.
- 3
Calcium check
One NHS guideline checks it 3 to 4 weeks after the course ends.
- 4
Daily dose
Your doctor may prescribe 800 to 2,000 IU a day.
Sources: NHS colecalciferol; Nottinghamshire APC
Only take more than 4,000 IU a day if a doctor tells you to. For what your result should look like after a course, see vitamin D levels after a loading dose.
Who should check before taking vitamin D?
The NHS says to tell your doctor before you start if you have:
- high calcium in your blood or pee
- kidney problems, or you’ve ever had kidney stones
- high vitamin D in your blood
- a rare condition called sarcoidosis
- calcium build-up in your body tissues or organs
- a peanut or soya allergy
Ask first too if you take digoxin (a heart medicine), water tablets such as bendroflumethiazide or indapamide, epilepsy medicines or steroids such as prednisolone. These can affect how vitamin D works, or raise your calcium.
Never stop or change a prescribed medicine without your prescriber.
How to pick your vitamin D dose
- Consider taking 10 micrograms (400 IU) a day from October to early March.
- Consider taking it all year if you’re rarely outdoors, cover most of your skin or have dark skin.
- Turn IU into micrograms by dividing by 40.
- Add up the vitamin D in every product you take.
- Keep the total at or under 100 micrograms (4,000 IU) a day, unless your doctor advises otherwise.
- Ask your doctor first if you have kidney problems or high calcium, or take digoxin, water tablets, epilepsy medicines or steroids.
Sources: NHS; NHS colecalciferol
When to speak to a GP
Get advice from your GP or 111 if:
- You’ve taken more than 4,000 IU in 1 day and it wasn’t a prescribed loading dose. The NHS says to contact 111 for advice now.
- While taking vitamin D, you pee more often, get swelling, are sick, feel confused, or get bone or joint pain or an irregular heartbeat. Some of these could be signs of too much calcium. Call your doctor or 111.
- You get a high temperature and a sharp pain in your side or one side of your lower back. It could be early kidney stones. Call your doctor or 111.
- You have bone pain that came on slowly and won’t go, or weak muscles that make stairs or getting up hard. An NHS guideline lists these as signs of low vitamin D.
Call 999 if your lips, mouth, throat or tongue suddenly swell, or you breathe very fast or struggle to breathe or swallow. Also call 999 if your skin, tongue or lips turn blue, grey or pale, or you suddenly become very confused, drowsy or dizzy. This can be a serious allergic reaction.
Want to know your level? See the vitamin D blood test. For the limits in more depth, see can you take too much vitamin D.