{"id":1673,"date":"2026-06-02T23:59:51","date_gmt":"2026-06-02T21:59:51","guid":{"rendered":"https:\/\/bezugla.de\/vitamin-d3-deficiency-symptoms-causes-and-how-to-take-targeted-countermeasures\/"},"modified":"2026-10-27T16:14:37","modified_gmt":"2026-10-27T15:14:37","slug":"vitamin-d3-deficiency-symptoms-causes-and-how-to-take-targeted-countermeasures","status":"publish","type":"post","link":"https:\/\/bezugla.de\/en\/vitamin-d3-deficiency-symptoms-causes-and-how-to-take-targeted-countermeasures\/","title":{"rendered":"Vitamin D3: Skin synthesis and 25-OH-D level"},"content":{"rendered":"\n
\"Vitamin<\/figure>\n\n

A vitamin D3 deficiency is best assessed via the 25-OH-D level in the blood, not through individual body signs or assumptions. Especially in Germany, the body\u2019s own synthesis via the skin is often limited in the winter months. Therefore: measure first, then plan intake individually and do not set the dosage high on your own on a long-term basis.<\/p>

Vitamin D has a special role among vitamins because the body can produce it in the skin when there is sufficient UV-B radiation. Foods also contribute to intake, but usually replace skin synthesis only to a limited extent. In practice, this means that sun exposure habits, season, everyday life and blood level should be considered together.<\/p>

How vitamin D3 is produced via the skin<\/h2>

The skin needs UV-B radiation to produce vitamin D3. This reaches the skin sufficiently mainly when the sun is high enough and uncovered areas of skin are exposed. In Berlin and other regions of Germany, this is especially relevant in spring and summer.<\/p>

Several factors are important: time of day, cloud cover, clothing, skin type, age, time spent outdoors and sun protection. Sun protection remains important, because protecting the skin and using the sun consciously are not mutually exclusive. Prolonged unprotected sun exposure is not a sensible strategy.<\/p>

An everyday example: someone who takes a short walk at midday in summer with their face, forearms and hands uncovered has different conditions from someone who commutes in the dark in the morning and evening and sits in an office during the day. Working from home can also mean that daylight is present, but hardly any direct UV-B radiation reaches the skin.<\/p>

Why it is often too little in winter in Germany<\/h2>

In autumn and winter, the sun is lower in the sky in Germany. As a result, less UV-B radiation reaches the earth\u2019s surface. At the same time, large areas of skin are covered by clothing, and many people spend most of the daylight hours indoors.<\/p>

Window glass is also a common misconception: bright light at the workplace or on the sofa by the window feels sunny, but it is not the same as direct UV-B radiation on the skin. A winter holiday in Germany also does not automatically compensate for the seasonal difference.<\/p>

Other typical situations in which the body\u2019s own synthesis may be low:<\/p>