Vitamin D: Deficiency, Dosage, Symptoms & Best Times to Get It

Vienna – A recent investigation by the Austrian consumer protection association, Verein für Konsumenteninformation (VKI), in collaboration with Germany’s Stiftung Warentest, has revealed that the vast majority of over-the-counter Vitamin D supplements are significantly overdosified, potentially posing health risks to consumers. The study, which examined 22 products, found that only two were deemed to contain a sensible dosage.

The VKI’s findings, released on February 28, 2026, highlight the dangers of self-medicating with Vitamin D supplements. Angela Tichy, project leader at the VKI, explained that Vitamin D is a fat-soluble vitamin stored in the body’s fat and muscle tissue, meaning excessive intake can accumulate and lead to health problems, including potential kidney failure. “This proves not excreted,” Tichy stated.

The organizations recommend a maximum daily intake of 800 International Units (I.E.) for long-term use, based on guidelines from the German Federal Institute for Risk Assessment and the German Nutrition Society. Many of the tested products exceeded this recommended dosage, with some being “strongly” overdosified, according to the VKI. Brands identified as having excessively high dosages include Alsiroyal, Dekristolvit, Hübner and Sanotact.

The VKI stresses that individuals suspecting a Vitamin D deficiency should consult a physician and undergo a blood test to determine their actual Vitamin D status before starting supplementation. Currently, in Austria, health insurance typically only covers the cost of Vitamin D status testing for individuals identified as being at risk.

Vitamin D plays a crucial role in regulating calcium and phosphate metabolism, promoting bone health, and influencing muscle function and the immune system. While the body can produce Vitamin D through sun exposure, particularly during the summer months, supplementation is often considered during periods of limited sunlight. However, the VKI warns against relying on supplements without professional medical guidance.

Certain risk groups, such as the elderly, residents of nursing homes, individuals with chronic illnesses, and those with obesity, may be more prone to Vitamin D deficiencies and could benefit from preventative supplementation, but only under medical supervision. The study’s findings underscore the importance of personalized medical advice regarding Vitamin D intake.

The full results of the VKI and Stiftung Warentest investigation are available in the February 2026 issue of the Austrian consumer magazine, KONSUMENT, and online at vki.at/VitaminD-2026.