Following should be looked for this change of taste sensation;
1) Oral thrush
2) Gum infection or gingivitis
3) Salivary gland diseases which decrease the saliva secretion
4) Zinc deficiency (disassociated taste disorder)
If these are not found to be associated, following needs to be looked for;
1) Post nasal drip
2) Sinus infections
3) Peridontal disease:dental infections/diseases
4) Gastroesophageal reflux disease
5) Alcohol and caffeine drinks which makes one dehydrated and thus this sensation
6) If you smoke this is a possibility
7) Medications; like antidepressants, the side effects can appear anytime
Drinking fluids and avoiding the caffeine and alcohol drinks is the first step of the management.
Examination by an ENT specialist and a dental surgeon is the second step to look for the cause. Inadequate saliva secretion, which can happen due to medications or because of lack of adequate fluids can also be responsible.
But it is never anything very serious (although annoying), so you should not be worried.
Please feel free for your follow up questions.