Your doctor probably will test you for tuberculosis and hepatitis B before you start taking a tumor necrosis factor (TNF) inhibitor to make sure you don't have either of those without knowing it. The drugs can make the effects of those infections worse. If you need antibiotics for an infection, you may have to stop taking your TNF inhibitor until the infection is cleared up. It's rare, but you also could be at higher risk of getting cancer if you take TNF inhibitors, including lymphoma or skin cancer. Some people may get serious brain reactions. Those with heart failure or multiple sclerosis shouldn't take these drugs.