Introduction: Vitamin D deficiency is associated with various types of disorders such as musculoskeletal disorder (rickets, osteomalacia, osteoporosis, myopathy), autoimmune disorders cardiovascular disorders (hypertension, congestive heart failure, myocardial infarction), kidney disorders, carcinoma), psychiatric disorders (depression, schizophrenia), skin disorders. Objectives: To Determine prevalence of serum Vitamin D deficiency in patients of chronic fatigue without any other systemic illness. Study design: Cross sectional study Setting: Department of Medicine, Central Park Teaching Hospital, Lahore Subjects: Total 150 patients with age 15-60 years of age of either gender having chronic Fatigue/ tiredness, generalized pains from more than 6 Months were enrolled. Methods: Study was conducted from 26th Jan 2020 till 25th Dec 2020 after approval of hospital ethical committee and written informed consent of patients. Serum vitamin D level performed to assess vitamin D level. Vitamin D deficiency was noted Proforma was filled after vitamin D level obtained. Data was entered and analyzed using SPS20. Results: In our sampled population total 150 patients were enrolled with mean age of 35.3±12.8 years. Most of patients belonged to elder age group i.e. 55.3%. There were 67.3% males and 32.7% females. Mean weight of sampled population was 70.9±11.7 kg, mean height was 156.8±15.1 cm and mean BMI was 28.7±5.9 kg/m2. Mean vitamin D levels was 39.16±11.2 ng/dl. Vitamin D deficiency was present in 64.7% patients. Conclusion: Vitamin D deficiency is common in patients with chronic fatigue.