It's great that your doctor is a knowledgeable athlete. I usually hover between 11 and 12, and when I'm 12 they'd tell me I'm normal. My husband started calling back and asking for all the numbers. I now have my husband write out a prescription for a complete iron screen, because last time I got into trouble because I was 12 but my stores were completely wiped out, just like Rita mentions. I've been supplementing for 6 months and can't get above 12 because my complete lack of stores.
I do know that a few years ago, I noticed a real drop in performance times, I ran a personal worst marathon and so I started training harder and harder and my 10k got slower and slower, until I actually stopped for awhile in one from complete exhaustion. I took iron and 4 weeks later, I was performing normally.