Jackson became a Navy officer in 1995, when he received his M.D. from the University of Texas Medical Branch. He graduated from the Undersea Medical Officer Program in 1996. Jackson had a series of operational postings, as officer-in-charge and diving medical officer at Explosive Ordnance Disposal Mobile Unit 8 at the naval base in Sigonella, Sicily and diving safety officer at the Naval Safety Center in Norfolk, Virginia. In 2001, he started a residency in emergency medicine, which he completed in 2004. He was clinical faculty physician in the Emergency Medical Residency Program in Portsmouth, Virginia for an additional year before being deployed to Iraq in 2005, where he worked as emergency medicine physician with a surgical shock trauma platoon in Taqaddum.