薛己出身医学世家，其父薛铠为太医院医官，他承袭家学，历任太医院院使，兼通内、外、妇、儿、正骨各科。他重视脾肾先后天之本，善用甘温补益之法调理虚损病证，是明代「温补学派」的重要先驱，对其后张景岳等人的温补理论影响颇深。

Born into a medical family — his father Xue Kai served as a physician in the Imperial Medical Academy — Xue Ji rose to head the Academy himself and was versed across internal medicine, surgery, gynecology, pediatrics, and bone-setting. He emphasized nourishing the spleen and kidney as the body's acquired and innate foundations, favoring warm, sweet tonifying methods for deficiency conditions. He is regarded as an important forerunner of the Ming-dynasty "Warming and Tonifying School," whose theories strongly influenced later figures such as Zhang Jingyue.