How many dosages of prednisone does it take before my leg from sciatica will feel better - i'm on a 6 day prescription ?

Maybe 1, maybe none: There is no "correct dose for use of steroids for nerve root pain. I prefer Medrol (methylprednisolone) dose pak but Prednisone is ok. Expect at least 5 or 6 days of treatment to be needed--maybe 2 weeks. Steroids long term are very risky & are never first-line treatment of sciatica. Some people never respond to steroids.

as usual, it depends: A course of Prednisone may in some instances provide relief of sciatica pain. If you do not experience relief after completing the course, you should speak to your doctor about other treatment options, including physical therapy and possibly epidural steroid injections.

One Medrol (methylprednisolone) Pack: However conventional wisdom is that if you haven't gotten enough relief with one Medrol (methylprednisolone) dose pack, unlikely its better to give more. In fact new research is showing that your risk of fracture increases almost 400% after one oral dosepack of steroids. You are better off getting an epidural steroid injection instead. Risk still exists but way less compared to oral steroids.