Well there are several things that are measured in a blood count that might be low, Connemmara - Haemoglobin level, Red Cell Count, White Cell Count, Platelets.
I am making the assumption that your are possibly wondering whether you might be suffering from an anaemia - where the Hb Level is typically lowered. The most common form of anaemia that presents itself is iron deficiency anaemia, and one of the most common symptoms is "Tired All the Time".
If you genuinely feel very tired and lethargic, if you are feeling breathless on exertion, or if you are especially pale, then you might have anaemia.
Should you have any concerns, it might be worth a consultation with your GP....