I am constantly tired and thirsty?

Need some tests. A person who is constantly tired and thirsty should see his primary care doctor, who will check the hydration status. Blood tests to look for diabetes, viral infections, anemia, and other problems will likely be done. Diabetes can cause this, but other illnesses can cause this also. The doctor will want to know what the person is drinking, when it all started, what happens while sleeping, etc...