07/04/2026
This is a great post explaining the science behind second daily iron dosing.
If you’re iron deficient, it’s important to take an appropriate dose, ideally second daily to optimise absorption and minimise side effects and get your levels rechecked after a specified period to tailor your treatment plan. It’s also REALLY important to figure out why you’re iron deficient and try to correct this if possible (I.e. manage heavy menstrual bleeding, improve diet, check for malabsorptive conditions like Coeliac Disease and other GI pathology (inflammatory bowel disease and cancer).
More discussion here on an old post of mine:
https://www.facebook.com/share/1Af87FMEY2/?mibextid=wwXIfr
Iron supplements are typically dosed daily, sometimes split into two doses. Both strategies fight the body's own regulatory system.
When you take 60 mg or more of elemental iron, the liver releases hepcidin, a hormone that binds ferroportin, the only iron export channel on intestinal cells, and degrades it. With ferroportin gone, the next dose sits in the enterocyte and never reaches the bloodstream. This shutdown lasts about 24 hours. By 48 hours, hepcidin clears and ferroportin is restored.
Stoffel et al. (2017) tested this in 40 iron-depleted (but not anemic) women given 60 mg ferrous sulfate on consecutive vs alternate days. The alternate-day group absorbed 21.8% per dose versus 16.3% for consecutive dosing. Total iron absorbed was also higher: 175 mg vs 131 mg.
A 2019 follow-up tested women with iron-deficiency anemia, a population where hepcidin is already partially suppressed by the body's demand for red blood cells. Even there, fractional absorption was 40-50% higher on alternate days. That's the stronger finding: the hepcidin rebound still limits absorption even when the body is actively trying to override it.
Caveat: all studies used ferrous sulfate in women. Whether the effect holds for other iron forms or in men is untested.
Moretti et al., Blood, 2015.
Stoffel et al., Lancet Haematology, 2017.
Stoffel et al., Blood, 2019.
