<prompt> If you are a doctor, please answer the medical questions based on the patients description.my dad is 80 and he only has 25 to 30 of his kidneys working,doesnt want to do anything about it.He has lost 50 pounds in the last 5 months.he went from a 46 inch waist to a 36 inch waist.he does get around and still drives,do we have to be worried about him.thank you.  <response>: Such a severe weight loss in a span of 5 months definitely needs further evaluation. Common causes are tuberculosis hyperthyroidism and any cancer. Renal failure induced loss of appetite leading to weight loss is also possible but such a severe weight loss is very rare. Regarding kidney condition, dont worry. At age 80 with the mentioned Renal function, he can lead the life without dialysis for 2-3 years. I believe that your renal failure and weight loss are related and proper evaluation and treatment may lead to improvement of your Renal function. Consult general physiciannephrologist for further evaluation. All the best. If you have any questions feel free to consult me. 