There are several things that commonly cause increased thirst. These are urinary tract infection, kidney infection, bladder stones, kidney disease, diabetes, Cushing's disease, and liver disease. Your dog needs a thorough examination by a veterinarian, blood work and urinalysis to determine the cause of his increased thirst.
Loss of appetite in dogs is not good sign if it last for more than 24 hours. Occasional loss of appetite is not a medical problem in dogs. If dogs don't eat for more than 24 hours then underlying disease can be responsible. Almost every disease in dogs can cause loss of appetite. Some common diseases that cause this condition in dogs are
1. Pain
2. All diseases of GI tract
3. Kidneys diseases
4. Diseases of blood
5. Diseases of mouth
6. Disease of eyes
7. Diseases of nose
8. Skin diseases
9. Diseases of brain and throat
10. Depression and anxiety
So, you should discuss your dog problem with your local vet.
1. Pain
2. All diseases of GI tract
3. Kidneys diseases
4. Diseases of blood
5. Diseases of mouth
6. Disease of eyes
7. Diseases of nose
8. Skin diseases
9. Diseases of brain and throat
10. Depression and anxiety
So, you should discuss your dog problem with your local vet.
Hope it is not par voe
Dogs can get diabetes. I would suggest a trip to the vet for a blood test.