Vitamin D is an ancient molecule, it is considered the oldest prohormone on Earth and gives support to every form of life from phytoplankton to the human species. The biological properties of this vitamin go far beyond maintaining phosphate and calcium homeostasis. The appearance of inadequate vitamin D status is associated with reduced sun exposure, low dietary intake and aging. The geographical position of different countries like continental part of the Republic of Croatia, is a risk factor for the occurrence of vitamin D deficiency in the population due to insufficient sunlight in these areas. The aim of this study was to determine the status of vitamin D in the adult population.The study determines vitamin D intake using a short (VDQ) and a questionnaire that determines the time exposure to the sun in the study group. The study subject are also provided with an International Physical Activity Questionnaire (IPAQ). Vitamin D levels were determined by measuring circulating 25-hydroxyvitamin D [25(OH)D] in serum. Serum sun exposure was tested as potential predictors of serum 25(OH)D concentration, vitamin D intake through diet (fish, margarine and dairy products), body mass index, age and physical (non) activity (strenuous physical activity, moderate physical activity, walking and sitting). Average serum 25 (OH) D level of (44 nmol / ml) is not only statistically but substantially lower than the optimum level of 75 nmol / L.