I’ve had blood transfusions, Fe infusions and Mg infusions with chemotherapy. The blood transfusions always because the haemoglobin was too low. I was once sent away because my neutrophils were too low.
The oncologist will tell you if it’s safe to proceed or if you can have a transfusion. It just adds time because pathology have to find a blood match as well as infuse you.
Hang in there!