“行医”常见的英文表达是 “practice medicine” 或 “engage in medical practice”。
practice medicine：这是最常用、最直接的表达，例如：He has been practicing medicine for over 30 years.（他行医已有30多年。）
engage in medical practice：这种表达更正式一些，常用于书面语或正式场合，例如：After graduating from medical school, she engaged in medical practice in her hometown.（从医学院毕业后，她在故乡行医。）