Well there are a number of conditions which can cause the appearance of a bitter taste in your mouth. The first one which is by far the commonest is acid reflux, this can even occur in the absence of burning in stomach or chest or even belching etc, this is because very minor cases of acid reflux in teh initial stages can present with taste changes in the mouth. If this is the case the you would be managed with drugs like OTC prilosec among dietary adjustments. If you are on warfarin then OTC zantac would be a better option.
Another cause of this can be nutritional deficiencies. Deficiencies of vitamin B12, zinc and magnesium can lead toi the development of altered taste sensations in the mouth. This can be corrected by using various supplements which are all available OTC.
Inflammation of the gums can also cause this problem, this would cause slightly red gums along with pain in the region in advanced cases as well as bleeding. The treatment is with antibiotics.
If you dont have pain, bad breath or any other symptom then the two most likely causes are either a deficiency of a nutrient or acid reflux and both can be treated easily. I would suggest that you try elevating the head of the bed by 30 degrees at night and eat your last meal atleast 2-3 hours before bedtime and if necessary using OTC zantac can be helpful (but before you use that do let me know which medications you are on so i can check and see if there are any interactions which should be considered).
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