Witamina D (25-OH)

Serum 25-hydroxyvitamin D measurement — the standard biomarker for assessing total vitamin D status from both dietary intake and sun exposure. At 70 PLN (~16.20 EUR), substantially cheaper than German private labs where the same assay typically costs 30-50 EUR. Essential screening at northern latitudes where UV-B exposure is insufficient for cutaneous synthesis for half the year.

25-hydroxyvitamin D (calcidiol) is the accepted clinical standard for evaluating vitamin D status. It reflects the combined contribution of dietary intake, supplementation, and cutaneous synthesis from ultraviolet-B radiation. The test measures total 25(OH)D, encompassing both D2 (ergocalciferol, plant-derived) and D3 (cholecalciferol, from animal sources and sunlight). Deficiency is defined as serum levels below 20 ng/mL (50 nmol/L), insufficiency as 20-30 ng/mL, and optimal status as 30-50 ng/mL. At Poznan's latitude (52.4 degrees N), effective cutaneous vitamin D synthesis occurs only from approximately late March through September. During the remaining months, supplementation is necessary for most individuals — the Polish Endocrine Society recommends 800-2000 IU daily for adults during autumn and winter. Vitamin D receptors are present in virtually every human tissue. Beyond the well-characterised role in calcium absorption and bone mineralisation, adequate vitamin D status is associated with immune regulation (reduced respiratory infection frequency), muscle strength and function, cardiovascular health, and mood regulation. Chronic deficiency triggers secondary hyperparathyroidism, which mobilises calcium from bone and accelerates osteoporotic bone loss. Population studies consistently show that 60-80% of Central European adults are vitamin D deficient during winter months. Poznan, sharing a similar latitude with Berlin, experiences the same seasonal UV limitation. Testing in late winter (February-March) captures the nadir of annual vitamin D status and is the most clinically informative timing. The 5 PLN collection fee applies per visit. Results are typically available within 48 hours.