I've had anemia before and it was brutal. Mine probably developed over a period of 2-3 months, but I though I was just slowly becoming a terrible runner.Are you tired all the time? Cause I could barely keep my eyes open all day.
Normal for ferritin is 12 - 300, but you want to be at least 60+. Hemoglobin should be 140-180 (or 14-18), as a runner the higher the better. My ferritin was 0.5 and my Hemoglobin was 105 and every run was a death march. Don't wait to get this tested.
Now I take iron pills on an empty stomach with vitamin C and try to not eat too much dairy and feel 100 times better.