Timing does seem to be a key in the success of disc injections. Injection in the first few weeks of disc herniation may have little effect since many patients get better on their own anyway. Most doctors advise an early plan of treatment using antiinflammatory drugs and physical therapy for the first six weeks.
Injection is considered if conservative care doesn't work to relieve pain. Many patients get relief from pain and other symptoms with one steroid injection for disc herniation. If no improvement occurs, you can get a second injection one week after the first. Some doctors will try a third injection a week after the second. After that, surgery to remove the disc is considered.
Your chances for long-term problems go up the longer you wait to treat a disc herniation. Muscle weakness, changes in sensation, and possible bowel or bladder problems can occur. Trying conservative treatment for up to three months doesn't seem to change the final outcome. This applies to most patients who crossover from conservative care to injection or disc removal.