The National Institute of Health and Care Excellence (NICE) and the Scientific Advisory Council on Nutrition (SACN) have advised that most people need 10 micrograms (400 units) of vitamin D per day in order to protect against deficiency.
They advise that everyone should take a vitamin D supplement between October and March of 10 micrograms (400 units) every day. This dose is safe and effective preventing vitamin D deficiency. This dose is recommended for adults, women who are pregnant or breastfeeding, young people, and children over 4 years old.
Some people are advised to take a daily 10 microgram vitamin D supplement all year round because they do not get enough sun exposure even in the summer time. This includes people who are indoors most of the time, for example, people who are frail, housebound, or live in a care home. Other people who should take a supplement all year are those who cover most of their skin when they are outside, or who have darker skin, such as people with African, African-Caribbean, or south Asian backgrounds.
Children who are between 1 and 4 years old should take 10 micrograms (400 units) of vitamin D every day throughout the year.
Babies who are less than one year old should have 8.5 micrograms (340 units) to 10 micrograms (400 units) of vitamin D once a day if they are breastfeeding, or if they are formula fed but drinking less than 500 ml a day. This is because formula milk is fortified already with vitamin D.