I am not a medical expert, but there are medications (injections) that can significantly boost white blood cell count. The one I was given is Udenyca; another one is Neulasta. In my case, I had chemo (day one) and the 5FU pump disconnected (day three). On day four, I got the Udenyca injection. Per insurance rules, the injection must be given a minimum of 24 hours after the pump finishes administering the fluroruracil. (I don't know why minimum 24 hours, but we were told if the injection was given even a minute or two earlier than 24 hours, insurance would deny coverage. So we and the nurses were extremely precise about noting and recording the timing.) I haven't had the Udenyca in a couple of cycles because my WBC counts were so high that I didn't need the injections any longer.

Forgot to add: The injection really hurts going in; the med is stored cold, and that makes it sting. But after that, I had no issues with it. However, some people have bone pain due to the increased activity in bone marrow. I was told to take antihistamines (Claritin in my case) to ward off the pain.