Low ferritin sucks: anything below 30 is low. And moving the dial on ferritin is a bisch. If you find out in one season it is low, and start supplementing aggressively, it will be the next season before it gets better. Better to supplement before you have a problem. Like yesterday.
It affects at least half of the distance girls on our team, including both of my daughters. One is celiac, so that makes it worse. Much worse.
The latest protocol, with limited scientific backing, is to take 2x iron every other day to improve absorption. We do it this way now, but I cannot say it is any better than taking 1x everyday.
Doctors don't know shite about endurance girls/women. Our pediatrician said daughter's iron was "normal", but did not give us the number. When asked, said it was 13. The bottom end is 12!!!!! Worst of all was the hematologist who looked at my celiac daughters ferritin of 14 and said "her iron levels couldn't possibly be the the cause of her fatigue." With emphasis "COULDN'T POSSIBLY BE THE CAUSE OF HER FATIGUE!!!!!!!!!". What a buffoon.
Celiac daughter runs mid-major D1 distance and her sports medicine people say minimum ferritin of 45. Needless to say, she redshirted with ferritin at 12, down from 14 a month before yet supplementing every g-dammed day for months.
Telltale signs of crashing ferritin: girl who starts the season well but starts to fade badly in races mid-season, for no apparent reason. Both daughters affected like this in 2017 XC season, we got iron-religion, supplemented like crazy, and got them up enough to win the state XC team championship. They finished 3 and 4 on the team. Whole family was white knuckled for weeks trying to get the ferritin up.
Summer training can easily mask a problem: kids do lots of running, but no workouts or races. The problem, at least for my kids, is that it only shows up at the end of races, not daily runs and not even most workouts. And other sports give no indication of a problem because they typically are not bumping up against their aerobic limits. One daughter played Spring lacrosse and low ferritin had no impact. So no incentive to supplement. Bad mistake. Remember it takes FOREVER to move ferritin so we should have been supplementing non-stop.
Hearsay, but friend says the Syracuse women are all on iron supplements, whether they want to or not. Source said they use Hema-Plex pills. We have used Pro-ferrin (heme iron pills) and Nova-Ferrum 125 (polysaccaride iron complex liquid) with decent success. (All three are available on Amazon Prime). The iron you choose can make a big difference on absorption and tolerance. Skip the non-heme iron completely. And for god sakes do not think you can tame this beast with iron-rich foods. That is taking a knife to a gunfight.
My advice is that every HS girl runner starts taking iron supplements NOW, unless you run for our arch rival. Once supplementing, get your blood tested. If you are above 30, then reduce (but not eliminate) the supplementation. In our area, a standard blood panel does not include ferritin or vitamin d, so ask for both. Get the results sent to you and track them over time. DO NOT take your doctors word when they say the results are normal. They are clueless. Get the numbers.
Some relevant research:
"Endurance exercise increases whole body iron turnover and iron losses via the gastrointestinal tract, hematuria and hemoglobinuria, elevating the estimated average requirement for athletes by 30–70%." No mention of menstruation, which adds to the problem.
https://www.nature.com/articles/1602479