A comorbidity is a concomitant but unrelated pathological or disease process, and comorbid conditions are coexisting medical conditions that are not necessarily compensable in a work-related injury but may affect the individual's treatment and recovery. Many comorbid conditions also are chronic health conditions that may interact with the sequelae of a compensable injury or illness and/or may affect the individual's health and abilities. In addition to the normal physiological changes of age, advancing age increases the number and severity of comorbid conditions, and this article examines three: obesity, diabetes, and heart disease. Obesity is associated with increasing workers’ compensation claims, medical and indemnity claim costs, and lost workdays; it is also a risk factor for type 2 diabetes, cancer, heart disease, and numerous other chronic and serious diseases. Hypoglycemia associated with diabetes can lead to falls and accidents, and diabetes may delay healing, predispose to infection, and cause peripheral neuropathies. Uncontrolled hypertension may be present in half of people with hypertension, leading to increased cardiac risk, especially if procedures or operations are needed. Claimants with comorbid conditions should be identified early in the claims process so claim handlers can use available comorbidity calculators to better plan for higher costs, longer disability, and more complex medical management. Nurse case managers can help the injured worker navigate the health system and act as a liaison between claims staff and medial providers.