Actually on the first day of fever and even for a day or two, initially when there is an infection, there is slight neutropenia (low segmenters or neurtrophils). Then the body fights the infection and the neutrophils rise and by day five of fever most blood pictures will show increased neutrophil count. Other than that it could be due to Vit B12 or folate deficiency or due to viral infection or autoimmune diseases or problems with spleen.
The low RBC and hemoglobin indicates anemia. Low hematocrit is due to anemia, malnutrition, destruction of red cells by spleen, bone marrow failure, and blood loss as in stomach ulcers and irritable bowel disease or in kidney stones. Leukemia, multiple myeloma and rheumatoid arthritis are the other problems with low hematocrit. Monocytosis or high monocyte count is seen in subacute bacterial endocarditis, syphilis, viral infections, kala azar, malaria, Rocky Mountain spotted fever, lupus, rheumatoid arthritis, IBS, lipid storage diseases, sarcoidosis etc.
So, anemia, spleen or bone marrow problems, infection and autoimmune disorders should be investigated for. Do discuss this with your doctor and get yourself examined. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.