Hi, Thanks for posting in HCM. I understand your concern. Low blood cell counts has nothing to do directly with your husband s death due to lung cancer. It could be due to poor dietary intake of essential vitamins and minerals like Vitamin B12, folic acid and iron, as evidenced by low Vitamin B12 levels. These vitamins and mineral aid in red blood cell and white blood cell maturation process, thus improving their counts. Since the counts seems to improve with Vitamin B12 supplementation, you can continue its intake as advised and check regularly to the improvement in the counts. Gradually, your blood cell counts should be back to normal. You can also supplement with iron and folic acid, as these elements also help to improve blood cell count. Hope the information provided would be helpful. All the best.