Background:Vitamin b12 deficiency is considera common nutritional deficiency in Indian population.Vitamin B12 deficiency related to hair and cutaneous features like hair-fall, and cutaneous pigmentation are not well described in literature. Aim:To study serum vitamin b12 level in relation to diffuse hair-fall and muco-cutaneouspigmentation. Study design: Case-control observational study Materials and methods:Total 240 patients presented with diffuse hair-fall or muco-cutaneous pigmentation were taken as cases and screened for serum vitamin b12 level at tertiary health care centre. Other 240 patients of same age group presented with other dermatological conditions were taken as control. Also associated symptoms like weakness, malaise, numbness, tingling, paresthesia, burning sole, glossitis, angular cheilitis, angular stomatitis, aphthous stomatitis, graying of hair, mild memory impairment, irritability, psychosis, delusion of paresthesia, dementia and depression were noted in each patient. Results:Out of 240 patient females: male ratio was 3.52:1. Vegetarian:non-vegetarian ratio was 3.36:1. Out of 240 patients 42% patient presented with hair fall, 33% with hyperpigmentation and 25% had both complain. Facial pigmentationin 20%, extra-facial in 15%, both (facial & extra-facial) in 45% of patients were noted. Mucosal pigmentation was present in 20%. Serum vitamin b12 level was low in 198 cases and 87 control. Hemoglobin level was low (<10 gm/dl) in 196 0f cases and 127 of control. Amongst 240 cases weakness in 58, malaise in 22, numbness in 5, tingling in 15, paresthesia in 2, burning sole in 108, glossitis in 76, angular stomatitis in 13, aphthous ulcer in 31, graying of hair in 92, memory impairment in 18, irritation in 64, psychosis and delusion of paresthesia in 1, dementia in 8 patients were noted. Conclusions:Vitamin B12 deficiency is not rare, but data are insufficient regarding its prevalence. In our study, 240 patients with diffuse hair fall and muco-cutaneous pigmentation as case group and 240 patients as control group were included. Among groups, vitamin b12 deficiency was found in 198 cases and 87 control. We found that there was significant association with vitamin b12 deficiency, diffuse hair fall and muco-cutaneous pigmentation as clinical markers for dermatologists.