How long does an epidural injection last?Epidural corticosteroid injection helps to decrease the inflammation around the nerve root. The anti-inflammatory medication reduces inflammation and irritation of the nerves. This can help ease pain caused by conditions such as herniated discs, spinal stenosis, and degenerative disc disease. The steroid starts kicking in between 2 to 7 days and the usual amount of time that a steroid epidural injection provides pain relief is roughly three months and in