When must I call for referral to spine doctor if I have lumbar spinal stenosis?

When you do not feel. Relief from the conservative treatment, then you have to seek his opinion.
If it is a problem. If your symptoms get too bothersome, then it is time to see a spine specialist. Check out Spine-health.com.
If no relief. If you have bothersome enough symptoms that have not been helped with treatment guided by your own doctor, ask for a referral.