Born 17 May 1732 in Görlitz, Gehler studied medicine from 1751 to 1758 at the University of Leipzig, where he was a pupil of physician and botanist Christian Gottlieb Ludwig.

While a student at Leipzig, he furthered his interest in natural sciences, publishing the mineralogical treatise, De characteribus fossilium externis (1757), as a result.

Following graduation, he continued his education by studying mineralogy in Freiberg and obstetrics in Strasbourg as a student of Johann Jakob Fried (1689–1769).

[1] After his return to Leipzig, he served as a lecturer in mineralogy, and in the meantime, maintained a successful medical practice, of which, he specialized in midwifery.

Later on at Leipzig, he successively held professorships in physiology (1773–1781), anatomy and surgery (1781–1784), pathology (1784–1789) and therapy (1789–1796).