Hi Tyson - Prednisone takes about 48 hours to get in your system. However, it can elevate your blood sugars like a diabetic which can cause the extreme thirst. Do you have any way to check your blood sugar? If you don't have a test meter, do you have a relative who has one who can test it for you? You really need to check the levels - I might even try an ER if I couldn't get it any other way. If it is high, you need to be treated until you can lower the prednisone.

Good luck!