Hello Thanks for consulting hcm Read your query as you feel rotten taste in mouth this can be due to vitamin deficiency , drug induced or depapillation of taste buds present on tongue . For this I will suggest you to consult oral surgeon or physcian for examination of tongue and complete blood investigation for heamoglobin and blood count to rule out deficiency. Inmeantime maintain proper oral hygiene by brushing and clean your tongue using tongue cleaner . You can take vitamin B supplements by consulting with local doctor . Hope this will help you.