In a Sri Lankan study, Papaya leaf extract was shown to increase the red blood cell count (erythropoiesis is blood cell manufacturing in the bones) significantly in mice in the lab in 21 days, where the platelets increased in three days time.
“…the RBC count in the test group increased from 6×106/µL to 9×106/ µL at Day 21 while it remained near constant in the control group (6×106/µL).” (See source below)
Chemotherapy has effect on the red blood cell manufacturing, according to experts at Healthline.com:
“Routine blood count monitoring is a crucial part of chemotherapy. That’s because the drugs can harm cells in the bone marrow, where blood is produced. This can result in several problems. Red blood cells carry oxygen to tissues. Anemia occurs when your body doesn’t produce enough red blood cells, making you feel extremely fatigued.” – See more at: http://www.healthline.com/health/cancer/effects-on-body#sthash.lbbPPkYb.dpuf
Does Carica papaya leaf-extract increase the platelet count? An experimental study in a murine model
Asian Pac J Trop Biomed. Sep 2013; 3(9): 720–724.