Jem'Hadar were bred in hatcheries and took only three days to go from infant to fully grown. They were designed lacking a crucial enzyme, which saw them requiring the drug ketracel-white to survive. In exchange they did not need to sleep or eat. They also possessed the ability to go invisible, which they referred to as shrouding.
If a Jem'Hadar did not get sufficient white they would suffer withdraw symptoms such as an inability to concentrate, feelings of pain, a lack of discipline, and no longer being able to shroud. They would get increasingly violent and kill anyone they could and even turn on each other before they died.
As the Jem'Hadars' only purpose was to serve as soldiers they died young and it was rare for them to live past the age of 15. If they lived to 20 years they were awarded the title "Honoured Elder".