To be clear, there is no one specific test, scan, or anything else of the sort that you can do to determine whether or not you need CBD oil for pain. Also, since cannabis is not yet recognized by the FDA, you unfortunately can’t really go to your doctor either and have them recommend it; until marijuana is FDA-approved, it cannot be prescribed by physicians.
Most products labeled "hemp oil" do not contain any CBD. Those are typically hemp seed oil which is more commonly used for cooking or to make salad dressing. If you want to buy CBD oil, you'll want to look for products that are labeled "CBD oil" or "hemp extract." To confirm that a product you're interested in has CBD in it, you'll want to look at their third-party lab reports. All reputable companies selling CBD oil products will make third-party lab reports available to you to confirm the presence of CBD.