Blood and other lab tests play a critical role in helping our Forum Health providers diagnose or confirm an arthritis diagnosis; determine if your body has inflammation and is making proteins called antibodies that are common to rheumatoid arthritis; monitor disease progress; check medication effectiveness; or determine if medications are causing potentially dangerous—but not evident—side effects. Most tests require drawing and testing the blood, but some may involve testing urine, joint fluid or even small pieces of skin or muscle.