Physicians may perform certain blood tests before or during treatment. For example, physicians frequently test for levels of lactate dehydrogenase (LDH) in the blood prior to treatment. Melanoma may be more difficult to treat in patients with elevated levels of LDH, particularly if the disease has spread to distant sites in the body. For patients with advanced-stage melanoma, physicians may perform other blood tests, including blood cell counts and blood chemistry tests. These tests help physicians see how well the bone marrow (the soft tissue in the center of most bones where blood cells are formed), liver and kidneys are functioning during treatment.