What is the name of the injection that builds white blood cells?

Answer 1

Are you sure you mean white blood cells and not red blood cells?

Erythropoietin (Darbepoetin alfa or Aranesp) stimulates erythroblast (red blood cell) precursors in the bone marrow to proliferate, eventually increasing the red blood cell count.

Source: I am a medical student.

Answer 2

The injection that helps stimulate the production of white blood cells is called Neupogen, also known as filgrastim. It is commonly used to prevent infections in patients undergoing chemotherapy or certain types of bone marrow transplants.