A. Weight loss in old cats is a serious sign that would need to be checked by your veterinarian as soon as possible. Several causes can lead to this state including metabolic/endocrine diseases such as hyperthyroidism and diabetes mellitus, tumors, chronic renal failure, liver diseases and many others. A blood test and urine analysis would be needed to effectively diagnose most of these diseases.
A. Older cats that are losing weight but still eating relatively normal are highly suspicious of 2 disease processes including 1) Hyperthyroidism and 2)Lymphoma . Neither of these conditions would necessarily cause pain, although lymphoma commonly will cause nausea and vomiting as well.
Both of these conditions require diagnostics to diagnose including bloodwork for hyperhyroidism and bloodwork + radiographs (sometimes doesn't pick up and need an ultrasound and/or lymph node testing) for Lymphoma. So I would recommend you schedule an appointment with your veterinarian to have your pet examined and the recommended testing done so that we know what we are dealing with and can treat it appropriately.
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