ABSTRACT The incidence of lifestyle disease like polycystic ovarian syndrome, Uccharaktachapa (~hypertension), Sthaulya (~obesity), Madhumeha (~Diabetes) as well as Iron deficiency Anemia are increasing day by day. Blood loss is one major cause of the iron deficiency. Women are at a higher risk as they lose blood during menstruation. Even a lack of iron in the diet can lead to this deficiency. Vitamin B12 is a nutrient that helps keep the body’s blood and nerve cells healthy and helps make DNA, the genetic material in all of the cells. Vitamin B12 also helps prevent megaloblastic anemia, a blood condition that makes people tired and weak. Vegetarians or vegans, menstruating and pregnant women and individuals who donate blood more frequently are at an increased risk of iron deficiency. As per the clinical features, Vit B12 deficiency can be considered among the types of Pandu Vyadhi. The aim of the study is to assess the role of Ayurvedic Nidanaparivarjana and Pathyapathya in Vit B12 deficiency as a first and the most important line of treatment in Ayurveda. In this case study, the strict vegetarian female, aged 27 years came with Vit B12 (also called cobalamin) deficiency with the symptoms i.e., tiredness, loss of appetite, weight loss, constipation, irritation and confusion. She was treated by Ayurveda with Nidanaparivarjana and Pathyapathya for 3 months without any allopathic intervention. After the completion of treatment protocol, her Vit B12 level became normal with marked improvement in the above-mentioned associated symptoms. Keywords: Ayurveda, Lifestyle disease, Nidanaparivarjana, Pandu Vyadhi, Pathyapathya, Vitamin B12 deficiency.