Upadacitinib is used alone or with other medications to treat rheumatoid arthritis (condition in which the body attacks its own joints causing pain, swelling, and loss of function) in people who are unable to take or have not responded well to one or more tumor necrosis factor (TNF) inhibitor medication(s). It is also used to treat psoriatic arthritis (a condition that causes joint pain and swelling and scales on the skin) in adults who are unable to take or did not respond to or tolerate one or more TNF inhibitor medication(s). Upadacitinib is also used to treat symptoms of eczema (atopic dermatitis; a skin disease that causes the skin to be dry and itchy and to sometimes develop red, scaly rashes) in adults and children 12 years and older who cannot use other medications for their condition or whose eczema has not responded to other medications. It is also used to treat ulcerative colitis (a condition that causes swelling and sores in the lining of the colon [large intestine] and rectum) in adults who are unable to take or who did not respond to one or more TNF inhibitor medication(s). Upadacitinib is used to treat ankylosing spondylitis (a condition in which the body attacks the joints of the spine and other areas, causing pain, swelling, and joint damage) in adults who are unable to take or who did not respond to one or more TNF inhibitor medication(s). Upadacitinib is in a class of medications called Janus kinase (JAK) inhibitors. It works by decreasing the activity of the immune system.