The lab-normal vs functional-optimal gap
Standard lab reference ranges flag ferritin as "normal" anywhere from 12-300 ng/mL for premenopausal women — a 25x range. But functional optimization data tells a different story: Trost et al. 2006 (J Am Acad Dermatol) demonstrated that ferritin under 30 ng/mL is associated with chronic telogen effluvium (hair shedding) and that repletion to ferritin 70+ improves shedding. Rushton 2002 (Clin Exp Dermatol) corroborated. Most dermatologists and functional clinicians treat ferritin under 70 ng/mL as "functionally low" even if labeled normal.
Why ferritin tracks better than other iron markers
Serum iron fluctuates by time of day, recent meals, menstrual cycle, and inflammation — making it a noisy single-point measurement. Hemoglobin only drops AFTER iron stores are exhausted, so it's a lagging indicator. Ferritin reflects total body iron reserves and is the earliest marker to drop in iron deficiency. The catch: ferritin is also an acute-phase protein that rises during inflammation, so an elevated ferritin during active infection or autoimmune flare doesn't necessarily mean iron sufficiency. Pair with CRP or hsCRP to rule out inflammation-driven false-high readings.
Optimal ranges by population
For hair, energy, exercise performance, and cognitive function — functional optimization research suggests targeting 50-100 ng/mL in premenopausal women, 70-150 ng/mL in men and post-menopausal women. Above 200 ng/mL warrants investigation (could indicate hemochromatosis or chronic inflammation). The bottom of the lab-normal range (12-30 ng/mL) is associated with hair shedding, fatigue, and exercise underperformance even without clinical anemia.
Repletion protocol
If ferritin is below 50 ng/mL and you have iron-deficiency symptoms (hair shedding, fatigue, exercise underperformance), Stoffel et al. 2017/2020 (Lancet Haematol + Blood) showed alternate-day dosing of 100-200mg elemental iron produces higher cumulative absorption than daily dosing. Take with vitamin C (50-100mg) for ~2x absorption (Lynch & Cook 1980). Retest ferritin at 12 weeks. See our iron supplement guide for product picks + the full protocol.
Primary sources: Trost LB et al. 2006 (J Am Acad Dermatol) — PubMed; Stoffel NU et al. 2017 (Lancet Haematol) alternate-day dosing.