How long does it take for a steroid epidural to affect your body?

12-24 hrs. But could be sooner as it is usually injected with local anesthetic that wears off in a few hrs and the anti-inflammatory effect of the steroid may be kicking in by then. A day or so for peak effect.
24-48 hours. Sometimes the local anesthetic will give a couple hours of relief but the steriod begins to active within 24-48 hours.