How much vitamin D do adults need?

Adults need 600 IU (15 micrograms) a day, or 800 IU (20 micrograms) over age 70 (US, NIH). In the UK: 10 micrograms (400 IU) a day (NHS).

What is the upper limit for vitamin D?

US: 4,000 IU (100 micrograms) a day. UK (NHS): up to 100 micrograms (4,000 IU) a day is unlikely to cause harm.

Which foods have vitamin D?

Oily fish such as salmon, trout and sardines, fortified milk and cereals, egg yolks, mushrooms grown under UV light, sunlight on the skin.

Vitamin D: what it does and how much you need

Vitamin D helps the body absorb calcium to build and keep strong bones, and plays a part in muscles, nerves and the immune system. Adults need 600 IU (15 micrograms) a day, or 800 IU (20 micrograms) over age 70, and the upper limit is 4,000 IU (100 micrograms) a day.

Checked 28 September 2026 with Supplement Check's data from the NIH fact sheet and NHS guidance · Adults only

General information, not medical advice. Check with a doctor or pharmacist before taking a supplement, especially if you are pregnant or breastfeeding, take any medicine, or are under 18.

In the UK

In the UK, adults need 10 micrograms (400 IU) a day, and the NHS says up to 100 micrograms (4,000 IU) a day is unlikely to cause harm. The NHS advises everyone to consider 10 micrograms a day in autumn and winter.

How much you need and the upper limit

	US (NIH)	UK (NHS)
Adults need	600 IU (15 micrograms) a day, or 800 IU (20 micrograms) over age 70	10 micrograms (400 IU) a day
Upper limit	4,000 IU (100 micrograms) a day	Up to 100 micrograms (4,000 IU) a day

The UK figure is the amount the NHS says is unlikely to cause harm. Figures are for adults.

Cautions

The NHS advises everyone to consider 10 micrograms a day in autumn and winter.

Food sources

Oily fish such as salmon, trout and sardines
Fortified milk and cereals
Egg yolks
Mushrooms grown under UV light
Sunlight on the skin

Forms on the label

Vitamin D2 (ergocalciferol) comes from plants and yeast, and D3 tends to raise blood levels a little more.
Vitamin D3 (cholecalciferol) is the form the skin makes in sunlight, and in most studies it raises blood levels a little more than D2.

Dose questions

Quick answers

What does vitamin D do?: Vitamin D helps the body absorb calcium to build and keep strong bones, and plays a part in muscles, nerves and the immune system.
How much vitamin D do adults need?: Adults need 600 IU (15 micrograms) a day, or 800 IU (20 micrograms) over age 70 (US, NIH). In the UK: 10 micrograms (400 IU) a day (NHS).
What is the upper limit for vitamin D?: US: 4,000 IU (100 micrograms) a day. UK (NHS): up to 100 micrograms (4,000 IU) a day is unlikely to cause harm.
Which foods have vitamin D?: Oily fish such as salmon, trout and sardines, fortified milk and cereals, egg yolks, mushrooms grown under UV light, sunlight on the skin.
What should I watch out for with vitamin D?: The NHS advises everyone to consider 10 micrograms a day in autumn and winter.

Sources

NIH Office of Dietary Supplements fact sheet
https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
NHS vitamins and minerals guidance
https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/

Ask Supplement Check yourself

Type a vitamin, mineral or supplement, a dose, or a product name, and get the daily need, the upper limit and any cautions. Open Supplement Check, free, no sign-up.

In Claude or any app that takes MCP connectors, add https://goodturn-mcp.pages.dev/supplementcheck/mcp and ask: “Is 5000 IU of vitamin D too much?”