Deficiency of vitamin D or hypovitaminosis D is widespread irrespective of age, gender, race and geography and has emerged as an important area of research. Vitamin D deficiency may lead to osteoporosis (osteomalacia in adults and rickets in children) along with calcium deficiency. Its deficiency is linked with low bone mass, weakness of muscles and increased risk of fracture. However, further research is needed to link deficiency of vitamin D with extra-skeletal consequences such as cancer, cardiovascular disease, diabetes, infections and autoimmune disorders. The causes of vitamin D deficiency include length and timing of sun exposure, amount of skin exposed, latitude, season, level of pollution in atmosphere, clothing, skin pigmentation, application of sunscreen, dietary factors and genetic factors. The primary source is sunlight, and the dietary sources include animal products such as fatty fish, food items fortified with vitamin D and supplements. Different cut-offs have been used to define hypovitaminosis D and its severity in different studies. Based on the findings from some Indian studies, a high prevalence of hypovitaminosis D was observed among different age groups. Hypovitaminosis D ranged from 84.9 to 100 per cent among school-going children, 42 to 74 per cent among pregnant women, 44.3 to 66.7 per cent among infants, 70 to 81.1 per cent among lactating mothers and 30 to 91.2 per cent among adults. To tackle the problem of hypovitaminosis D in India, vitamin D fortification in staple foods, supplementation of vitamin D along with calcium, inclusion of local fortified food items in supplementary nutrition programmes launched by the government, cooperation from stakeholders from food industry and creating awareness among physicians and the general population may help in combating the problem to some extent.