How long does it take oral steroids to start working for siatic nerve?

Hours to days: In general oral/enteral steroids work within hours and reach full effects over the course of days. I will temper that statement with, in the case of steroids for sciatica, it's unclear how much steroids really help. Anecdoctally, as in from personal experience, many physicians still utilize oral steroids for this case, but man studies suggest limited to no benefit at all. Best of luck.

Outcome: Oral or intravenous steroids may have a lag period of about 48 hrs prior to initial benefit, and the effect may build over a few more days, but if you have not noted at least some minor benefit after 5-7 days, unlikely this will improve beyond that point, and you might do better with an epidural steroid injection.