if your ferritin is consistently low, you may have iron deficiency. If your haemoglobin level is below normal, then you should seriously consider iron replacement.
First we have to make the diagnosis, you have to look at the iron saturation (it should be low ) and total iron binding capacity (it should be raised).
If you have these results, then consider increasing iron in your diet such as eat more red meat, take iron supplements.
Concurrently, you have to see your doctor and find out the cause of the low ferritin level. Is it blood loss in the gut, blood loss through menses or reduced dietary iron intake