Background: Thyroid disorder is one of the most common encountered endocrinological disorder. Vitamin B–12 has the largest and most chemically complex structure of all the vitamins. Deficiency of vitamin B12 in thyroid disorder patients might exaggerate the clinical outcome. Objective: • To evaluate vitamin B12 levels in thyroid disorder patients. Material and method: The study was done in 50 thyroid disorder patients of Sir Takhatsinhji Maharaj hospital, Bhavnagar. Patient clinical findings and history was noted. Patient blood routine investigations CBC, RFT, with serum vitamin B12 levels and Thyroid function test were done. Result: We screened 50 thyroid disorder patients. Vitamin B12 deficiency was found among 30 patients having thyroid disorders. Conclusion: Thyroid disorders adversely affect the vitamin B12 levels, so routine assessment of vitamin B12 levels will help doctor for better management and favorable outcome. SUMMARY This study was carried out in Department of Medicine, Government Medical College, and Sir Takhatsinhji General Hospital, Bhavnagar. The study was done on 50 patients with thyroid disorders with a measurement of vitamin B12 levels in admitted and outdoor patients at Sir Takhatsinhji General Hospital, Bhavnagar. Detailed history and examination were done. Routine blood investigations, serum vitamin B12 levels, serum TSH, T3 and T4 levels was done in all patients. Following are the salient features of the present study • Thyroid disorder and vitamin B12 deficiency are both, more common among 41 – 50 years people. • Thyroid disorder is more common among the females. • Subclinical hypothyroidism is among the more common thyroid disorder. • Vitamin B12 deficiency is more common in the Hypothyroid patients. Macrocytic hypochromic anemia is more prevalent among the people with thyroid disorder having vitamin B12 deficiency.