Vitamin D supplements

How to choose your vitamin D

Vitamin D contributes to the normal absorption and utilisation of calcium and phosphorus, to the maintenance of normal bones and normal muscle function, and to the normal functioning of the immune system. These five criteria will help you choose between the products on this page.

1. Convert IU to micrograms

Labels use IU (international units) or µg (micrograms). 1 µg = 40 IU: 1000 IU is 25 µg, 2000 IU is 50 µg and 4000 IU is 100 µg. The nutrient reference value is 5 µg (200 IU) per day.

2. Choose the dose carefully

EFSA has set the tolerable upper intake level at 100 µg (4000 IU) per dayfor adults and adolescents from 11 years of age, and at 50 µg (2000 IU) for children aged 1 to 10 years, including all sources. On this page there are products with 5000, 10 000 and 14 000 IU per unit: they are intended for use under the guidance of a healthcare professional. Vitamin D accumulates in the body, and only a blood test indicates your levels.

3. Alone or with vitamin K2

Many formulas combine vitamin D3 with K2 (usually in the MK-7 form). Vitamin K contributes to the maintenance of normal bones and to normal blood clotting. If you take anticoagulants, talk to your doctor before choosing a formula with K2.

4. The format

• Capsules and softgels: practical, with a fixed dose.
• Drops and liquids: allow for dosage adjustment, useful for children and those who cannot swallow capsules.
• Spray: applied in the mouth, without water.
• Gummies: pleasant to take, but check the sugar content and keep them out of the reach of children.
• Liposomal: the vitamin comes wrapped in phospholipid vesicles; it is a formulation technology, not another form of vitamin D.

5. Origin and how to take

Vitamin D3 is usually obtained from lanolin; in vegan versions, from lichens. As it is fat-soluble, take it with a meal that contains some fat. Do not exceed the daily dose indicated on the label and add up the vitamin D from all the supplements you take, including multivitamins.