Vitamin D

Helps the gut absorb calcium and phosphate, keeps bones and muscles strong and supports immunity. The skin makes it from sunlight.

If you are short of it

Rickets (children)

Soft, bent bones, bowed legs, delayed walking and growth.

Osteomalacia (adults)

Aching bones and muscle weakness because bones do not harden properly.

Osteoporosis

Thin, fragile bones that fracture easily; many causes, calcium and vitamin D are two of them.

Possible signs

Bone or joint pain
Muscle weakness
Tiredness, low energy
Muscle cramps or twitching
Low mood or irritability
Frequent infections
Fragile bones, easy fractures

These signs are common and have many other causes. They are clues, not proof; a blood test and a doctor can tell.

Who is more at risk

People with little sun on their skin (covering clothes, indoor work, constant sunscreen, dark skin, long winters), older adults, breastfed infants, obesity, kidney or liver disease, fat malabsorption. Deficiency is common even in sunny countries.

Foods rich in Vitamin D

Food	Serving	Amount	women 19–50	men 19–50
Salmon	100 g cooked	16.7 NIH	111%	111%
Mackerel	100 g cooked	12	80%	80%
Cod liver oil	1 teaspoon (5 ml)	11.3 NIH	75%	75%
Sardines (canned, with bones)	1 can (90 g drained)	4.4 NIH	29%	29%
Milk (fortified)	1 cup (240 ml)	2.9 NIH	19%	19%
Eggs	2 large eggs	2.2 NIH	15%	15%
Fortified breakfast cereal	1 bowl (30 g) — check the label	2 NIH	13%	13%
Tuna (canned, light)	85 g, half a can	1 NIH	6.7%	6.7%
Beef liver	85 g cooked	1 NIH	6.7%	6.7%
Cheese (cheddar type)	40 g, about 2 slices	0.4 NIH	2.7%	2.7%
Mushrooms (cooked)	½ cup (80 g)	0.2	1.3%	1.3%

Unit: mcg. Share of the daily amount. Values marked NIH were checked against the food tables of the NIH Office of Dietary Supplements; the others are approximate and unchecked. Real foods vary with variety, brand, soil and cooking.

Plan a day of meals rich in Vitamin D

As a supplement

D3 (cholecalciferol) usually raises blood levels better than D2. Take with the biggest meal. Breastfed babies are usually given 400 IU (10 mcg) drops daily on the paediatrician’s advice.

Too much

Above the upper limit for months it raises blood calcium: nausea, thirst, kidney stones, confusion. Doses to treat a deficiency are set by a doctor after a blood test (25-OH vitamin D).

How much you need each day

Group	Recommended	Upper limit
Infants 0–6 months	10	25
Infants 7–12 months	10	38
Children 1–3 years	15	63
Children 4–8 years	15	75
Children 9–13 years	15	100
Boys 14–18 years	15	100
Girls 14–18 years	15	100
Men 19–30 years	15	100
Women 19–30 years	15	100
Men 31–50 years	15	100
Women 31–50 years	15	100
Men 51–70 years	15	100
Women 51–70 years	15	100
Men over 70	20	100
Women over 70	20	100
Pregnant 14–18 years	15	100
Pregnant 19–30 years	15	100
Pregnant 31–50 years	15	100
Breastfeeding 14–18 years	15	100
Breastfeeding 19–30 years	15	100
Breastfeeding 31–50 years	15	100

Unit: mcg · 1 mcg = 40 IU. US/Canada Dietary Reference Intakes (National Academies), as summarised by the NIH Office of Dietary Supplements. Other countries’ values differ slightly. These are amounts for healthy people, not treatment doses.

Interactions

Works together · Calcium
Vitamin D increases calcium absorption. Low vitamin D makes calcium supplements work poorly.

Take care · Calcium
Very high calcium together with very high vitamin D can raise blood calcium. Stay within the upper limits.

Works together · Magnesium
Magnesium is needed to activate vitamin D, so low magnesium can blunt the effect of vitamin D.

Take care · Vitamin A
Very high preformed vitamin A can oppose vitamin D and weaken bones. Avoid long-term high-dose vitamin A.

Works together · Vitamin K
Vitamin K works with vitamin D and calcium to place calcium in bones. Evidence for K2 supplements is still limited.

Medicines and habits to mention to your doctor

Water pills (furosemide, thiazides)
Furosemide-type pills wash out magnesium, zinc, thiamin and calcium. Thiazides raise blood calcium, so calcium plus vitamin D supplements need a doctor’s check.

Anti-seizure medicines (phenytoin, carbamazepine, valproate)
They can lower folate, vitamin D, vitamin K and biotin. Ask about bone health and folate, especially before pregnancy.

Steroids by mouth (prednisolone)
Long courses thin bones. Calcium and vitamin D are usually advised; your doctor will plan it.

Fat blockers (orlistat) and bile-acid binders
They reduce absorption of fat-soluble vitamins A, D, E and K. Take a multivitamin at a different time, at least 2 hours apart.

Open in the Vita Guide app

General information for healthy people. It does not diagnose, treat or replace advice from a doctor, pharmacist or dietitian. Not reviewed by a clinician.

Page updated: 2026-10-08 · By Prof. E. Shalaan, Applied Sciences and AI (ASAI)