What causes you to have shaking chills when you are sick?

Fever, blood infect. Shaking chills mostly go with blood infection called sepsis and are associated with high fever and white blood cell count. Allergic reactions and certain drug reactions can also cause this. Of course it is possible to just get very cold while sick. Then the chills might have to do with that but don't take any chances. Sepsis can be life threatening, get checked out if you reach that state.