Compare vitamin D3 + K2

Vitamin D contributes to the normal absorption and utilisation of calcium and phosphorus, to the maintenance of normal bones, teeth and muscle function, and to the normal function of the immune system. Vitamin K contributes to normal blood clotting and to the maintenance of normal bones. These are the authorised claims that manufacturers in the EU are allowed to use.

The body produces most of its vitamin D itself when UVB radiation reaches the skin. In Germany, the sun is barely strong enough for this from roughly October to March. Food – such as oily sea fish, eggs or mushrooms – provides only comparatively small amounts.

Vitamin D is stated in micrograms (µg) or International Units (IU; IE in German). The rule is: 1 µg equals 40 IU, so 20 µg equals 800 IU. The German Nutrition Society (DGE) gives an estimated value of 20 µg per day for adults when the body produces none of its own. The German Federal Institute for Risk Assessment (BfR) recommends a maximum level of 20 µg vitamin D per daily dose in food supplements.

Many products on sale contain considerably more – 5,000, 10,000 or 20,000 IU per tablet or as a “weekly depot”. Such amounts should not be taken without medical advice, because a long-term overdose can lead to raised calcium levels in the blood. So don't just look for “high-dose”; look at the actual amount per day.

Vitamin K2 occurs in several forms; supplements usually contain menaquinone-7 (MK-7). The term “all-trans” refers to the spatial structure of the molecule; the all-trans form is considered the biologically active one. Manufacturers also advertise branded raw materials. Whether combining D3 and K2 offers healthy people any additional benefit over vitamin D alone has not been conclusively established by science.

Especially important: anyone taking anticoagulants of the vitamin K antagonist type (coumarins) should only use products containing vitamin K after consulting their doctor, as they can affect how these medicines work.

Food supplements are no substitute for a balanced, varied diet or a healthy lifestyle. If you have a pre-existing condition, are pregnant or breastfeeding, or take medication regularly, ask a doctor or pharmacist for advice before taking them. Do not exceed the recommended daily intake stated on the pack. The information on this page is for general guidance only and is no substitute for individual advice.