Vitamin D (Colecalciferol)

Vitamin D is the one supplement essentially everyone in the UK should take for part of the year. Between October and early March our sunlight is too weak for skin to make any, whatever the weather looks like.

Who should take it, and how much

Everyone over the age of one is advised to take 10 micrograms (400 IU) daily from October to early March.

Some people should take it all year round:

• Anyone who is rarely outdoors, housebound, or in a care home
• Anyone who usually covers most of their skin outdoors
• People with darker skin from African, African-Caribbean or South Asian backgrounds, who make less vitamin D from UK sunlight

Babies from birth to one year need 8.5 to 10 micrograms daily, including breastfed babies. Formula-fed babies do not need extra until they are having less than 500ml of formula a day, since formula is fortified.

Higher prescribed doses

If a blood test shows deficiency, a higher loading dose is often prescribed for several weeks, followed by a maintenance dose. Follow those instructions rather than the general advice above.

Vitamin D is also prescribed alongside calcium in osteoporosis, and with bisphosphonates such as alendronic acid.

Safety

More is not better. Taking more than 100 micrograms (4,000 IU) daily long term is not recommended without medical advice, and very high doses cause a dangerous rise in blood calcium — symptoms include nausea, vomiting, excessive thirst, frequent urination, constipation, confusion and muscle weakness.

Tell your prescriber if you have kidney stones, kidney disease, sarcoidosis, or take digoxin or thiazide diuretics.

Take it with food, particularly a meal containing some fat, as it is fat-soluble and absorbs better that way.

If you are pregnant or have a child under four and receive certain benefits, the Healthy Start scheme provides free vitamins including vitamin D — many eligible families never claim it.

Frequently asked questions