A. For a cat that is drinking more and most likely urinating more too, and who is losing weight, I would be suspicious of an endocrine disorder. Endocrine disorders include: #1 in older cats -Hyperthyroidism
I would highly recommend that you get your cats blood tested to find out what is going on internally so that treatment can be implemented. The sooner you treat underlying diseases the better you have at managing them and extending the life of your pet.
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