Hello, and thanks for writing in.
Common causes for increased thirst and urination include diabetes, kidney disease, urinary tract infections, bladder stones, adrenal gland disease (Cushing's disease). The only way to find out is to have him examined by your veterinarian and have blood tests and a urine test run. Treatment can vary quite a bit for these different things, so the tests are needed to get a diagnosis, and to decide on treatment.
I hope this helps. Let me know if I can assist you further.
Thanks for your reply.
We commonly see problems like diabetes, kidney problems, and Cushing's disease in middle age to older dogs. Urinary tract infections and bladder stones can happen at any age. Eating things that shouldn't be eaten, can potentially cause the increase in thirst and urination. We see this sometimes with things that may be irritating to the digestive tract or salty things.
Let me know if I can help you further.