Vitamin D deficiency is widespread in the population and associated with many symptoms. The normal vitamin D concentration in an adult’s blood should be between 20 and 60 ng/ ml during the summer months. Values below 10 ng/ml are associated with an increased risk of rachitis (see below) in the child and osteomalacia (see below) in adults. Also less pronounced defects lead to various problems in the patient. These include bone and muscular pain, sometimes similar to rheumatic diseases, muscle weakness and psychological symptoms that are similar that are similar to depression (depression and vitamin D deficiency) and can even be confused with this. Often the vitamin D deficiency is associated with other deficiencies, such as iron and vitamin B12 deficiency. Which is why these values should always be examined in any periodical laboratory control, especially when the symptoms above are present. Vitamin D is formed by the skin when exposed to the sun. Lack of exposure to the sun during the winter months, in people with poor outdoor activity (for example older bedridden people) or wearing heavy clothing may result in vitamin D deficiency. The skin type also plays an important role. The darker is the skin, the stronger sun rays are filtered and less vitamin D is formed. This should be considered in dark-skinned patients who have moved from sunny areas to the north. Another form of vitamin D deficiency may be due to decreased dietary intake, e.g. in celiac people. Vitamin D deficiency leads to problems with the bone metabolism. The bone matrix is insufficiently mineralized in vitamin D deficiency and the formed bone is less resistant (rickets in the child, osteomalacia in adults).this is important at any age, but especially in the childhood and postmenopausal woman. With vitamin D deficiency, less calcium is absorbed with the diet. Therefore, you should always pay attention to a sufficient vitamin D content when calcium is given. Calcium fulfills many important functions in our body. In the meantime, several scientific studies have shown that vitamin d deficiency also plays a role as a risk factor in other diseases such as cardiovascular diseases, cancer and immunologic diseases. The connection between vitamin d deficiency and depression will be discussed in more detail in my next article (depression and vitamin D deficiency). The therapy of the vitamin D deficiency consists in the, usually oral substitution of the vitamin D. This should take place only after previous measurement of the vitamin D content in the blood and only after consultation with a physician.