If your lab range begins at 10 and yours is only 5 then your ferretin is low and you ought to be supplementing. My lab uses a 15 - 165 range and my doctor wants me up at 125. a lot of doctors simply don't care, so long as you don't show up as being anemic. A lot don't even request a 'ferretin' result.
The doctor who really helped me out a lot also always requested a Vitamin D and B12 test. These 2 are important and they should also be up at the high end of the lab range.
The lowest my ferretin got to was 8 and i felt like death. My gp at the time simply told me to begin taking an iron supplement ASAP!! Different doctors view it with varying degrees of seriousness. Everyone on this board has felt better at a higher level of ferretin and most knowledgable doctors will want your level higher.
I agree with Audrey - you probably should be taking iron supplements. I had a ferritinof5 and I was sent to a hematologist by my GP and she put me on iron. Perhaps you need to contact your doctor again to discuss - don't be bashful to demand some better answers.