Greger received a Doctor of Medicine degree in 1955 and Ph.D. in 1966 from Medical University of Lodz.
Greger received a Doctor of Medicine degree from Medical University of Lodz in 1955. Ten years later he earned his Ph.D. from the same university.
Greger began his career as an assistant professor and then an associate professor at Medical University of Lodz in 1955 and held the positions for thirty five years. In 1981, he was appointed a vice dean and dean in 1986 at the same university. In 1990, Janusz became a vice-rector at Medical University of Lodz and held the position until 1993. Since 1990 he is a professor and head of biochemistry department at that university.
Greger is a member of Polish Biochemical Society, Polish Medical Society, Lodz Scientific Society and New York Academy of Sciences.
On February 28, 1968 Janusz Greger married Krystyna Maria Mika. They have two children.