Overview

• Germany’s Federal Institute for Risk Assessment cites studies linking very high intermittent doses, such as 500 micrograms every 20 days, to increased risks of falls and fractures.
• The agency cautions that bolus products raise the chance of dosing mistakes when taken more often than intended.
• Safety and benefit data for combined high-dose vitamin D with vitamin K2 are limited, so such regimens should be used only under medical supervision.
• Leading medical societies say healthy adults generally do not need routine blood tests or winter supplementation.
• Consumer guidance sets a 20 microgram (800 IU) daily limit for self-supplementation and recommends 20 micrograms daily for care-home residents, while large randomized evidence shows no clear protection against acute respiratory infections.