Know that Medicare approves of their use. "Locum tenens" is a Latin phrase meaning "to hold the place of, to substitute for." In a medical setting, a locum tenens physician fills a short-term staffing need while the practice's regular physician is gone for a time, or when the practice needs additional help during a peak season. The amount of time a locum tenens works at the practice can range from a few days to several weeks. Good to know: LT physicians are a Medicare concept. That means payers who follow Medicare's guidelines also embrace the concept and follow the associated Medicare coding guidelines.