http://www.medications.com/effect/view/17413 I have been on prednisone for weeks at a time due to asthma. In 2002-2003 I had been on it for a total of 3-4 months (shortest being 10 days and longest being 6 weeks) I gained 10 lbs in 5 days laying in the hospital bed...from 154 to 164 and then up to 17