IntroductionThe most important function of vitamin D is to maintain normal calcium homeostasis. Various factors play an important role but the most significant aspect of its normal physiological functioning is exposure to sunlight, therefore, it is also known as the sunshine vitamin. In adults, a prolonged deficiency of vitamin D (calcitriol) can lead to osteomalacia while a lower deficiency (insufficiency) is associated with various non-specific symptoms.Vitamin D deficiency has been observed in developed and developing countries, including the Middle East and the subcontinent. Vitamin D is mandatory for the maintenance of health due to the presence of its highly specific receptors, Vitamin D receptors, in all body tissues and its regulatory role in the encoding of more than 200 genes. The deficiency of Vitamin D, therefore, could affect any tissue or body system. Most interventions for this are done through outpatient departments (OPDs).The burden of vitamin D deficiency is affected by seasonal variation in our part of the world as well as internationally; data show a marked variation, however. Generalized body ache is a vague symptom. It is one of the most common complaints seen at the OPD and can be a manifestation of many a disease. But a correlation with low vitamin D levels has been observed previously. Whether this relation is affected by seasonal variation remains unascertained and data on the above-mentioned relationship for Pakistan are scarce.ObjectiveWe aim to evaluate the incidence of vitamin D deficiency in different seasons in the adult Karachi population presenting in medical OPDs with a generalized body ache.Materials and methodsThis study was conducted at Medical Ward 5, Jinnah Postgraduate Medical Center, Karachi, from January 2016 to December 2016. Data were collected from the OPD that was held twice-weekly (Mondays and Fridays). Only patients who exclusively complained of "generalized body ache" were inducted into the study. Patients with minor complaints, such as headache, backache, fatigue, and lethargy, were also seen only if there were no comorbidity at all. Meticulous lab and clinical workup were done to rule out potentially not-so-benign causes of the symptoms.Patients 18 years or older were inducted into the study. Once written consent was taken, Vitamin D levels were carried out via the COBAS (Roche Diagnostics, Mannheim, Germany) method. A vitamin D level of ≤30 ng/ml was considered deficient. Results were obtained within a week, and data were recorded and analyzed. Summer was defined as three months either side of the summer solstice (June 21) and winter was defined as three months either side of the winter solstice (December 21).ResultsA total of 577 patients were inducted into the study. The mean age of the patients was 39.33 ± 10.23 years. The patients were predominantly female (72.7%) and housewives. Of these, 298 (51.64%) had a vitamin D deficiency; in summer, the incidence was 44.23% and in winter, it was 60.37%. The mean level of vitamin D in deficient patients was 25.06±8.74...