The loss of sense of taste on tongue is due to distortion of taste buds
may be due to different causes-
like bacterial or fungal infection
,zink deficiensy,use of certain drugs etc.
Treatment is to be decided after knowing the causative factor.
Blood Zink levels testing, cellular cultures, & sometimes Electro physiological tests ,MRI
are done to investigate the problem.
I would advice you to consult a Physician for the examination,investigations & treatment.