wo ist vitamin d drin — what can you do yourself?

Vitamin D is primarily produced in the skin through sunlight exposure. On your own, you can aim for 15–30 minutes of sun on face and arms without sunscreen daily (depending on skin type and season). Dietary sources include fatty fish (salmon, herring, mackerel), cod liver oil, egg yolks, and fortified foods (e.g., margarine, some dairy). In Germany, supplementation of 800 IU (20 µg) per day is recommended for adults when endogenous production is insufficient – e.g., in winter or with limited sun exposure. At-home test kits (e.g., blood spot tests from pharmacies) can measure your vitamin D level, but they are not a substitute for medical diagnosis. If you have symptoms of deficiency or a very low level, consult a doctor. Evidence for benefit of supplementation in people with normal levels is mixed; excessive intake (above 100 µg/day) can be toxic.