Public Health England advises adults and children over four to consider 10 micrograms (400IU) a day from October to March, and year-round for anyone who spends little time outdoors, covers their skin, or has darker skin. Many practitioners work with higher amounts, typically 1,000IU to 4,000IU, based on a blood test. The safe upper level for adults is 100 micrograms (4,000IU) a day unless a doctor advises otherwise. If you are unsure, a simple blood test through your GP or a home kit will tell you where you stand.

D3 (cholecalciferol) is the form the skin makes in sunlight and the form found in animal foods. D2 (ergocalciferol) comes from plant sources and fungi. Studies consistently show D3 raises and maintains blood levels more effectively than D2, which is why every product in this range uses D3. Our vegan option uses D3 extracted from lichen, so plant-based customers do not have to settle for D2.

Vitamin D increases calcium absorption from food. Vitamin K2 contributes to normal blood clotting and to the maintenance of normal bones, and practitioners commonly pair the two on the reasoning that K2 supports calcium being used in bone. If you take vitamin D at higher amounts for a long period, a combined D3 and K2 product is the option most practitioners would suggest. Anyone on blood-thinning medication such as warfarin should check with their doctor before taking K2.

Vitamin D is fat-soluble, so both formats contain it in an oil base for absorption. Capsules give a fixed amount per day. Oil drops let you measure precisely, take a smaller dose for a child, or increase gradually. Drops are also the answer for anyone who cannot swallow capsules. Whichever you choose, take it with a meal that contains some fat.

Yes. Unlike water-soluble vitamins, the body stores vitamin D, and very high intakes over months can raise blood calcium to harmful levels. Stay within the label guidance unless a doctor or practitioner has advised otherwise on the basis of a blood test, and do not combine several products that each contain vitamin D without adding up the total. Symptoms of excess include nausea, thirst and frequent urination, and warrant a call to your GP.