High single doses of vitamin D via food supplements at intervals of days or weeks associated with health risks

Note: The original source of this report is the BfR website - see BfR Opinion No 031/2025 issued 3 September 2025

• Food supplements containing vitamin D are available in various dosages. Preparations are also available in which very high single doses ("bolus doses") of vitamin D are to be taken at intervals of several days to weeks. Some preparations also contain vitamin K2.
• High bolus doses of vitamin D (e.g. 500 micrograms (μg) every 20 days) can lead to vitamin D concentrations in the blood that, according to studies, pose health risks, especially for people who already have a very good supply of vitamin D.
• Studies have shown that taking very high bolus doses of vitamin D can increase the risk of, for example, falls and bone fractures. Other studies have found neither health impairments (at lower doses in some cases) nor health benefits.
• According to the German Federal Institute for Risk Assessment (BfR), food supplements that are to be taken as bolus doses at specific intervals also pose a problem in that they increase the risk of improper intake. This means that they may be taken more frequently than intended, e.g. daily instead of every 20, 10 or 7 days. This increases the risk of health impairments.
• For cases in which supplementation is necessary, the BfR recommends taking a lower-dose preparation daily. The BfR recommends a maximum amount of 20 μg of vitamin D per daily dose in food supplements, as this is not expected to pose any health risks in the long term, even when other sources of vitamin D are taken into account. Bolus doses of vitamin D and vitamin K should only be taken on medical advice and under medical supervision.
• This opinion assesses the intake of high bolus doses of vitamin D via food supplements. It does not apply to medical drugs containing vitamin D in different doses and with different application regimens, which may be prescribed by a doctor for certain diseases, for the prevention of diseases or in cases of deficiency.
• From a legal perspective, food supplements are considered food. Unlike medical drugs, food supplements are not subject to an official approval process.