Vitamins & minerals

Vitamin D: what to look for when buying

Published 16.08.2026Content reviewed 15.08.20267 min read

In brief: Vitamin D products differ mainly in the amount per recommended daily portion, in their form and in whether other nutrients are included. They become comparable via the amount in micrograms (µg); 1 µg of vitamin D equals 40 IU. A high % NRV value is neither a safety assessment nor a quality feature. What matters for assessment is the dose, the intake schedule, other vitamin D sources you consume and the product-specific notices.

By the SteloSupps editorial team · Editorial status: 15 August 2026 · Editorial and source policy

µg or IU? Both express the same amount

Vitamin D packs show two units: micrograms (µg) and international units (IU; in German: I.E.). The conversion is simple:

1 µg vitamin D = 40 IU – and the other way round: 40 IU = 1 µg.

A few common values:

  • 5 µg = 200 IU
  • 20 µg = 800 IU
  • 25 µg = 1000 IU

For nutrition labelling, vitamin D is stated in µg; an amount in IU may appear in addition. So compare products by the amount of vitamin D in µg per recommended daily portion. The IU figure is simply a different unit and not an additional strength.

NRV, DGE estimated value, BfR proposed maximum level and EFSA UL

The EU nutrient reference value (NRV) for vitamin D for adults is 5 µg. A daily portion of 25 µg therefore corresponds to 500% NRV. The NRV is a reference value for labelling – not a personal requirement and not a safety upper limit. 3

This must be distinguished from the DGE estimated value: for adolescents and adults without the body's own vitamin D synthesis, the German Nutrition Society states 20 µg per day. This value is not the same as the EU NRV and does not mean that everyone must take 20 µg from a food supplement across the board. 47

The German Federal Institute for Risk Assessment (BfR) recommends no more than 20 µg of vitamin D per daily dose in food supplements. This is a scientifically derived proposal for a maximum level, not a legally established limit. A daily portion of 25 µg is above this BfR proposal. 68

EFSA's Tolerable Upper Intake Level (UL) for adults is 100 µg of vitamin D per day from all food sources, including fortified foods and food supplements. The UL is not a recommended daily dose, not a target intake and not a quality benchmark for an individual product. 5

Authorised claims for vitamin D

For vitamin D, the following claims, among others, are authorised, provided the specific product meets the legal conditions on amounts: 2

Vitamin D contributes to the maintenance of normal bones.

Vitamin D contributes to the maintenance of normal muscle function.

Vitamin D contributes to the normal function of the immune system.

Mandatory notice: Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Do not exceed the stated recommended daily dose.

Note on health claims: These claims may only be used for products that meet the legal requirements for a source of vitamin D. The daily portion and directions for use stated on the respective product are decisive. 1

In particular, disease-related promises of cure, treatment or prevention are not permitted. Other claims about vitamin D may only be used if they are authorised in the EU Register and the specific product meets the respective conditions of use. 1

Single product or combination?

Vitamin D is offered as a single product and in combination with other nutrients. For the comparison, the ingredients and amounts per recommended daily portion are decisive:

  • Vitamin D3 alone – contains vitamin D without additional vitamin K, calcium or magnesium. Compare the amount of vitamin D per recommended daily portion and check other products you use at the same time.
  • Vitamin D3 + K2 – contains vitamin K2 in addition to vitamin D. Compare the declared amounts of vitamin D and vitamin K per recommended daily portion. Adding K2 is not a general requirement for taking vitamin D; according to the BfR, an additional health benefit of the combination has not been proven. People taking anticoagulant medicines should seek medical advice before using food supplements containing vitamin K. 8
  • Combination with calcium and magnesium – contains other minerals in addition to vitamin D. So compare the amount per recommended daily portion for each nutrient and take other products you use at the same time into account.

The longest list of ingredients is not automatically the most suitable. What matters is the declared composition of the specific product.

Intake: follow the directions instead of changing the dose yourself

Vitamin D is fat-soluble. For timing, preparation and daily amount, the directions for use of the specific product are decisive. We don't derive a general obligation to take it with a meal from its fat solubility alone.

Where needed, the BfR recommends taking a lower-dose supplement daily rather than high single doses at intervals of several days or weeks. Such high bolus doses should only be taken on medical instruction and under medical supervision. 6

Do not exceed the stated recommended daily dose. Don't change the dose or intake interval on your own. With medical conditions, regular medication, during pregnancy or breastfeeding, and when using several vitamin D products at the same time, observe the product-specific notices and, if in doubt, seek advice from a doctor or pharmacist. For products containing vitamin K, this applies in particular to people taking anticoagulant medicines. 8

How to compare in practice

  1. Compare the amount of vitamin D in µg per recommended daily portion. For conversion: IU divided by 40 gives µg.
  2. Interpret the % NRV correctly: 100% NRV corresponds to 5 µg. The % NRV is not a safety or quality assessment.
  3. Distinguish between the EU NRV, the DGE estimated value, the BfR proposed maximum level and the EFSA UL; these values have different functions.
  4. Take other vitamin D sources you consume into account, for example other food supplements and fortified foods.
  5. For combination products, also check the amounts of vitamin K, calcium, magnesium and other nutrients contained.
  6. Follow the directions for use of the specific product and don't change the dose or intake interval on your own.

How to find the details on the pack is shown in our guide Reading labels correctly; the basics of NRV and total intake are covered in Vitamins and minerals: requirements, intake and overdosing.

Vitamin D at SteloSupps

EVÄM Vitamin D3 effervescent tablets – 25 µg vitamin D3 (1000 IU; 500% NRV) per recommended daily portion. Dissolve one effervescent tablet in water daily according to the directions for use.

Vitamin D3 + K2 Complex Drinking Shots – according to the supplier documentation, 15 µg vitamin D3 and 50 µg vitamin K2 per recommended daily portion of one drink vial.

EVÄM Calcium + Magnesium + D3 effervescent tablets – 5 µg vitamin D3 (100% NRV) per recommended daily portion.

View vitamin D3 effervescent tabletsAll vitamin D products

More guidance in our guide:

Frequently asked questions

How do I convert µg to IU?

1 µg of vitamin D equals 40 IU. So: µg times 40 gives IU; IU divided by 40 gives µg. 25 µg equals 1000 IU.

How should 500% NRV be interpreted?

For vitamin D, 500% NRV equals 25 µg, because the EU NRV for adults is 5 µg. The NRV is not a safety upper limit. However, a daily portion of 25 µg is above the BfR proposed maximum level of 20 µg for food supplements. The EFSA UL of 100 µg per day refers to adults' long-term total intake from all food sources and is not a recommended product dose.

Do I need K2 when taking vitamin D?

Adding K2 is not a general requirement for taking vitamin D. Vitamin D and vitamin K are two separate nutrients, each with its own labelling per recommended daily portion. According to the BfR, an additional health benefit of combining high-dose vitamin D with K2 has not been proven. People taking anticoagulant medicines should only use food supplements containing vitamin K after consulting a doctor.

Can I overdose on vitamin D?

A health-relevant oversupply can arise in particular from persistently excessive intake from food supplements or from high bolus doses. Follow the directions for use, take other vitamin D sources into account and don't change the dose or intake interval on your own. High bolus doses should only be taken on medical instruction and under medical supervision.

Does vitamin D have to be taken with a meal?

Vitamin D is fat-soluble. Whether and how a specific product should be taken with a meal depends on its directions for use. We don't derive a general obligation to take it with a meal from its fat solubility alone.

Sources

Sources as of: 15 August 2026.

  1. Regulation (EC) No 1924/2006 – nutrition and health claims (in particular Art. 10)
  2. Regulation (EU) No 432/2012 – authorised health claims (consolidated version)
  3. Regulation (EU) No 1169/2011, Annex XIII – EU nutrient reference values (consolidated version)
  4. DGE: Reference values for vitamin D – estimated value 20 µg/day without endogenous synthesis (in German)
  5. EFSA Journal (2023): Tolerable upper intake level for vitamin D – 100 µg/day for adults
  6. BfR opinion No 031/2025: High single doses of vitamin D pose health risks (in German)
  7. BfR: Selected questions and answers on vitamin D (in German)
  8. BfR (2023): High-dose food supplements with vitamin D – additional benefit of D + K not proven (in German)

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