Your doctor will usually be able to diagnose low back pain from your symptoms and there will be no need for further tests. If however, your symptoms don't improve after a few weeks or you have some red flag symptoms she/he may refer you to a back clinic to have an X-ray, a CT scan, an MRI scan or various blood tests. These tests are used to find out if you have a more specific underlying cause for your back pain.
Attribution: BUPA