 [ Symptoms ] is it harmful to use cannabis while taking prednisone [ Disease ] well unless you live in one of the states that permits the use of medical marijuana and you have a valid prescription for it then the law says you should not be using it at all but let is assume you do have a medical marijuana prescription in general i would not think smoking cannabis would interfere with the action of prednisone prednisone is a steroid preparation that treats inflammatory conditions i must add however that few studies have been done to evaluate potential drug interactions with marijuana so the real answer to your question is we just do not know if using marijuana while taking prednisone is harmful or not hope that helps