Hi, The persistent bitter test in mouth has many cause few of them are mentioned below in order of most common occurrence to least likely cause. 1) Dehydration- decrease water intake - 2) Poor oral health is also a main reason for the metallic taste 3) sinus infection 4) heartburn, acid reflux problems 5) magnesium supplements, vitamin supplements, antihistamines 6) Persistent bitter taste as an initial symptom of amyotrophic lateral sclerosis. (very rare) Now Amyotrophic lateral sclerosis (ALS) is very rare cause and not to worry to much about it and here is information regarding ALS, it is characterised by progressive degeneration of upper and lower motor neurones. Clinical symptoms involve weakness, dysphagia, dysarthria, muscle atrophy and fasciculations, hyperreflexia, spasticity, Babinski signs, and clonus. The disease initially presented with a persistent bitter “metallic” taste. ADIVCE: consult physician and check any of the above mentioned causes listed from 1-5, are most common and need to be addressed appropriately with their respective treatment. To get rid of bitter taste, diagnosis needs to be made first. Hope this answer has addressed your concern. Dr. JAY PATEL