Overview
- Germany’s nutrition society recommends 20 micrograms (800 IU) per day when sun exposure is inadequate, with 1 microgram equaling 40 IU and higher needs varying by individual and body weight.
- The Endocrine Society prefers daily supplementation over intermittent high doses to keep levels steady, and intakes above 2,000 IU should be medically supervised given the EFSA upper limit of 4,000 IU.
- Vitamin D status is measured as serum 25‑hydroxyvitamin D after a blood draw, and statutory insurers in Germany typically reimburse tests only with suspected deficiency, making routine checks often a private expense.
- In Germany, effective skin synthesis generally occurs from March to October and can require 5–25 minutes of sun on face, hands and arms, while diet usually supplies only 10–20% through fatty fish, eggs, dairy, fortified foods and some mushrooms.
- Experts caution that combining vitamin D with magnesium or vitamin K2 is not automatically necessary, advise spacing supplements from medicines, and warn that excessive dosing can cause adverse effects including nausea, vomiting and kidney issues.