This case study examines the interconnections between creatine, creatinine, muscle physiology, and kidney function. “Jan,” a woman in her mid-40s, leaves her doctor’s appointment with questions about her slightly elevated creatinine levels. After her doctor shares that creatinine levels in the blood are used as a measure of kidney function, she begins to worry. Could her elevated creatinine be related to the creatine supplement she has been using for workout recovery? What is the connection between creatine and creatinine? Could this supplement be damaging her kidneys? Students read the brief story and then answer a set of questions, either independently or in small groups, exploring the dynamics of creatinine in relation to skeletal muscle and kidney function. This case was developed for first-year physician assistant students who have completed a year of anatomy and physiology. The case could also be used in an upper-level physiology course for undergraduate majors in any field of biology.