Low blood counts (pancytopenia) can be due to a variety of causes including aplastic/hypoplastic anaemia, megaloblastic anaemia, myelodysplastic syndromes, acute or chronic leukaemia etc. Please get a complete blood count, reticulocyte count, peripheral smear and bone marrow (aspiration & trephine biopsy) examinations done as these would help find the underlying cause. Also helpful would be serum LDH homocysteine and methylmalonic acid estimations.
Megaloblastic anaemia due to cobalamin (vitamin B12) and folate deficiencies is very likely a possibility but this can be decided after the above mentioned tests and treatment with B12 and folate. When treated adequately, elevated levels of LDH and indirect bilirubin fall rapidly and reticulocyte count increases within 3-5 days and peaks in 4-10 days. The Hb rises approximately 1 g/wk. The rise in Hb & reticulocytes along with a fall in LDH levels is used for monitoring response. The reduced white cell and platelet counts are usually restored to normal within days after initiating treatment. If the Hb does not rise approximately at the expected rate or is not normal within 2 months, other causes of anaemia need to be considered