Sunlight, food and the units on the label: a concise guide to vitamin D3.
01 · What does it do?
Vitamin D promotes calcium absorption and contributes to the maintenance of bones. D3, called cholecalciferol, is one of its forms. Learn more on the NIH website.
02 · Sun and nutrition
The skin produces vitamin D thanks to UVB rays; season, age, and other factors influence this process. This is not an invitation to forgo sunscreen. The role of sunlight.
Fatty fish, egg yolks, and certain fortified foods are dietary sources. Sources according to the NHS.
03 · How to read µg and IU
One microgram of vitamin D corresponds to 40 international units: therefore, 1,000 IU is equivalent to 25 µg. This is a conversion, not a recommended dose for everyone. Units of measurement and quantities.
04 · An individual choice
More does not mean better: prolonged excess can be harmful. To choose a suitable supplement, especially if you have medical conditions, consult a healthcare professional. Precautions.
The Bio-Clock formula
Check the ingredients, format, and instructions for use of Bio-Clock Vitamin D3.
Updated October 7, 2026. Supplements are not a substitute for a varied and balanced diet and a healthy lifestyle.