My ferritin was 13 two years ago, and I was symptomatic. I had horribly strong heart palpitations that I'd never experienced before, and I had zero endurance. I remember going on hikes and feeling like I'd keel over. And going up hills, I'd be tingling all over. I just thought I was out of shape. I also was losing my hair without noticing it. My hairdresser noticed the regrowth months later and said I'd had a "major shed."

I think a double-red blood donation sent me into that state. It didn't help matters that I had also recently switched to Centrum Silver (with less iron than normal vitamins). Considering I was still menstruating, that was really stupid.

After tearing up my digestive tract with iron supplements, I started eating more iron-rich food and cooking in ironware. I've been at 18 for the past two years now. My PCP isn't concerned how low it is, but the gastroenterologist I just saw for something unrelated wasn't thrilled with it. With the PN to boot, he tested me for celiac disease...which was negative.

Interestingly, my serum iron spiked too high last year on my iron rich diet, but my ferritin was still just 18. I resumed donating blood, and my serum iron was normal this year while my ferritin was still 18. Maybe I have the defective peptide MrsD mentioned.