Vitamin D: reading µg and IU, daily or weekly, D3 or D2

This guide helps you read a label: it does not replace the advice of a healthcare professional.

In the European Union, the vitamin D content of a food supplement is declared in micrograms (µg): this is the unit set by Directive 2002/46/EC. Some German packs also show “I.E.” (Internationale Einheiten), meaning international units (IU).

EFSA gives the equivalence: 1 µg of vitamin D (D3 or D2) = 40 IU. One IU is therefore 0.025 µg. To go from IU to µg, divide by 40; to go from µg to IU, multiply by 40.

The label also shows a “% NRV” figure. It is calculated on the labelling nutrient reference value, set at 5 µg for vitamin D by Regulation (EU) No 1169/2011: a 25 µg tablet therefore shows 500 %. This labelling value is not the EFSA reference intake presented below.

The table below only converts units: it does not recommend any amount. To find out whether a dosage suits you, ask your doctor or pharmacist.

In 2016, EFSA set adequate intakes: 10 µg (400 IU) a day for infants aged 7 to 11 months, and 15 µg (600 IU) a day for children and adolescents aged 1 to 17, adults, pregnant women and breastfeeding women. These values assume minimal sun exposure: the skin makes vitamin D in the sun, which reduces the amount needed from the diet. To set them, EFSA used a target blood concentration of 25(OH)D of 50 nmol/L.

In 2023, EFSA reassessed the tolerable upper intake level (UL): the maximum level of long-term daily intake from all sources (foods, fortified foods, beverages and supplements) that is not expected to pose a health risk. It is meant to protect the whole general population, including sensitive individuals. A limit is neither a target nor a recommended dose.

The effect used is persistent hypercalciuria (a lasting excess of calcium in the urine), which EFSA considers a possibly early sign of excess vitamin D. It identified 250 µg a day as the lowest dose associated with this effect in two controlled human trials, then divided that figure by an uncertainty factor of 2.5: hence 100 µg a day for adults.

The infant limits (25 µg before 6 months, 35 µg from 7 to 11 months) were set by EFSA in 2018 and carried over unchanged into the 2023 opinion. According to EFSA, European populations are unlikely to exceed these limits, except regular users of food supplements containing high doses of vitamin D.

Some German products are taken once a week (“Wochendepot” on the box): a single intake then contains the amount of several days. To compare two labels, you can divide the weekly amount by seven: 5,600 IU (140 µg) a week averages 800 IU (20 µg) a day. This is only a reading aid: EFSA intakes and limits are all expressed per day, and EFSA has set no weekly limit.

In its 2023 opinion, EFSA used trials in which vitamin D was given daily or weekly, and excluded those in which it was given less often than once a week, because of the uncertainties in extrapolating their results to daily intake. It also notes “some evidence” that high doses given in one go, monthly or yearly, increase the risk of falls and fractures, with no known mechanism. Choosing a daily or a weekly intake is therefore a matter for your doctor or pharmacist.

For EFSA, “vitamin D” is the common name for two forms: cholecalciferol (vitamin D3), which the skin makes under UVB rays, and ergocalciferol (vitamin D2). Both are authorised in EU food supplements, and EFSA counts 1 µg of D2 the same as 1 µg of D3 in its values. It cites studies in which D3 raised blood 25(OH)D more than D2, considers the clinical relevance of that difference unclear, and lists the comparison of the two forms among the questions needing further research.

Some products combine vitamin D and vitamin K2. Regulation (EU) No 432/2012 lists claims nutrient by nutrient and contains none for the combination of the two. For vitamin K, it authorises among others “Vitamin K contributes to normal blood clotting”: if you take an anticoagulant medicine, ask your doctor or pharmacist before any supplement that contains it.

Regulation (EU) No 432/2012 authorises the following claims for vitamin D (official text, consolidated version of 20 August 2025). “The claim may be used only for food which is at least a source of vitamin D” within the meaning of Regulation (EC) No 1924/2006.

– “Vitamin D contributes to normal absorption/utilisation of calcium and phosphorus”

– “Vitamin D contributes to normal blood calcium levels”

– “Vitamin D contributes to the maintenance of normal bones”

– “Vitamin D contributes to the maintenance of normal muscle function”

– “Vitamin D contributes to the maintenance of normal teeth”

– “Vitamin D contributes to the normal function of the immune system”

– “Vitamin D has a role in the process of cell division”

EFSA uses the blood concentration of 25(OH)D as an appropriate marker of vitamin D status. Your doctor decides whether it should be measured and interprets the result in light of your situation. The 50 nmol/L value quoted above is the target EFSA used to set reference intakes for a population.

According to EFSA, the skin's production of vitamin D depends on environmental factors (latitude, season) and individual ones (skin type and pigmentation, time spent outdoors, sunscreen, clothing); it is less efficient with age. EFSA also notes that several studies report lower 25(OH)D levels with a higher body mass index or body fat. Living in a sunny country such as Morocco does not, on its own, tell you what your status is.

Before choosing a product, and all the more during pregnancy, breastfeeding, for a child or alongside ongoing treatment, ask your doctor, midwife or pharmacist. The products are gathered on the vitamin D page; see also calcium, pregnancy and breastfeeding vitamins and the Mivolis brand.

Sources consulted on 7 November 2026.

1. EFSA (European Food Safety Authority), NDA Panel — Scientific opinion on the tolerable upper intake level for vitamin D, including the derivation of a conversion factor for calcidiol monohydrate, EFSA Journal, 2023 (https://doi.org/10.2903/j.efsa.2023.8145; full text: https://pmc.ncbi.nlm.nih.gov/articles/PMC10407748/). Used for: 1 µg = 40 IU, D2 and D3 counted equally, upper limits by age, hypercalciuria, spaced-out doses, skin production.

2. EFSA, NDA Panel — Dietary reference values for vitamin D, EFSA Journal, 2016 (https://doi.org/10.2903/j.efsa.2016.4547). Used for: adequate intakes, 50 nmol/L target.

3. EFSA — Vitamin D: EFSA sets dietary reference values, press release of 28 October 2016 (https://www.efsa.europa.eu/en/press/news/161028). Used for: adequate intakes, minimal sun exposure.

4. Commission Regulation (EU) No 432/2012 of 16 May 2012 (authorised health claims), consolidated version of 20 August 2025 (https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:02012R0432-20250820). Used for: vitamin D and vitamin K claims, “source of vitamin D” condition.

5. Directive 2002/46/EC of the European Parliament and of the Council of 10 June 2002 on food supplements, Article 8 and Annexes I and II (https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32002L0046). Used for: µg unit, authorised D3 and D2 forms.

6. Regulation (EU) No 1169/2011 of the European Parliament and of the Council of 25 October 2011 on the provision of food information to consumers, Annex XIII (https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32011R1169). Used for: 5 µg nutrient reference value.