Your iron is "normal" and you're still exhausted: the ferritin story

There is a specific kind of tired that laboratory reference ranges were not built to catch. If you've felt it, you know exactly what I mean.

What ferritin actually measures

Ferritin is the protein your body uses to store iron. Think of it as the gauge on the tank, where hemoglobin is the fuel currently in the engine. Standard lab ranges for ferritin in women often start around 10-15 ng/mL. So a woman with a ferritin of 15 gets a "normal" result. No flag, no follow-up, no phone call.

Here's the problem: symptoms of iron deficiency show up well before anemia does. You can have a completely normal hemoglobin and an empty tank. Those early symptoms:

• fatigue - hair shedding - restless legs - cold intolerance - brain fog - workouts that feel inexplicably harder

The research on iron-deficient non-anemic women bears this out: randomized trials have found iron supplementation reduced fatigue in non-anemic women with ferritin under 50 (Vaucher et al., CMAJ, 2012). Under 50! A value that sails through most lab reports as unremarkable.

Most clinicians who look closely at this consider ferritin under 30 clearly deficient regardless of hemoglobin, and many aim for 50-100 in women with symptoms. One honest complication worth knowing: ferritin is also an inflammation marker, so it can read falsely reassuring if you're fighting a cold or have an inflammatory condition. That's why it's often ordered alongside CRP.

Why this is disproportionately a women's issue

No mystery here: menstruation is a monthly iron withdrawal, pregnancy is a nine-month one, and heavy periods (common and undertreated in perimenopause) can outpace any reasonable diet.

If your ferritin is low: food first

Heme iron (red meat, poultry, fish) absorbs several times better than plant iron. A few rules that matter:

• Pair plant sources with vitamin C, which meaningfully boosts absorption. - Keep coffee, tea, and calcium away from iron-rich meals. All three block absorption, and the coffee effect is bigger than most people expect. Sorry.

If you supplement

Ferrous bisglycinate, 25 mg is gentler on the gut than the ferrous sulfate your pharmacy hands out, and every-other-day dosing appears to absorb as well or better than daily, thanks to a hormone called hepcidin that spikes after each dose and blocks the next one. Less frequent, better absorbed, fewer digestive complaints. The body is occasionally kind like that.

Two cautions, stated plainly:

• Don't supplement iron blind. Excess iron is genuinely harmful and some people have a genetic condition (hemochromatosis) that makes it dangerous. Test, supplement if low, retest in 8-12 weeks. - If the reason your ferritin keeps dropping is heavy periods, the supplement is a patch, not the answer. That conversation belongs with your doctor.

"Normal" was never the goal. Functioning is the goal.