Low red blood cell count but no noticeable symptoms.

I've always had a low red blood cell count. Usually right at the bottom of normal. My doctor just said as long as it's consistent and not causing problems it's ok. I'm wondering if maybe it is causing problems but it's just normal to me.

I don't really feel fatigued all the time or anything but maybe I'd feel even better if my levels were higher.

Any ideas or should I just leave it alone? If it's something simple like taking B12 I may as well give it a try and see what happens.