A system of a combined climbing harness and medical tourniquet, and a method for using the system. A looped thigh strap portion of a climbing harness is detachable from the harness belt for separate alternative use as an emergency tourniquet for the user or a patient. The looped thigh strap is provided with features and components to facilitate its use as a functional tourniquet for either an arm or a leg, while nevertheless in ordinary use allowing it to serve as a component of a climbing harness.