PHYS-36 · Principle
Always tired, ferritin 28: could it be iron?
It could. Athletes lose iron and may absorb less after hard sessions; whether low stores without anaemia slow you is disputed, and inflammation raises ferritin. Test before supplementing.
How the body works, agreed across the reviews below; a study entry shows what one experiment measured.
Practical Application
Always tired, ferritin 28: could it be iron? It could. Athletes lose iron and may absorb less after hard sessions; whether low stores without anaemia slow you is disputed, and inflammation raises ferritin. Test before supplementing.
What it means for training: test before an altitude or heat block and when tiredness has no other explanation; iron only after a blood test, with the dose set by a physician (SYNTH-06).
What it does not mean: supplementing blind: long-term iron with normal or high ferritin brings nothing and may harm (Clénin 2015); or that one lab's cut-off is a diagnosis.
Mechanism
Exercise losses come from red-cell breakdown, blood in urine, sweat and gut bleeding (Peeling 2008); over a third of surveyed female marathoners and elite athletes reported heavy menstrual bleeding (REF-573).
Exercise inflammation (IL-6) raises hepcidin, the hormone that blocks iron uptake from the gut and its release from stores (Peeling 2008; Pasricha 2021); across individual data, session duration was the largest factor in the hepcidin change, about 44% of its variance (Fensham 2023).
Supplements raised ferritin mainly when it started very low (13 trials, Šmid 2024), whose authors add that exercise inflammation can raise ferritin above true stores.
Common misreading
"Tired, so take iron"; "ferritin is normal, so stores are fine" when measured after hard training or illness.
Safety (base practice): anaemia, very low ferritin or heavy bleeding go to a physician (SYNTH-06).