Daily vs every-other-day iron in pregnancy

How do the options compare?

Options are stacked on five dimensions relevant to pregnancy use: mainstream OB guidance, pregnancy-specific evidence, dosing predictability, onset, and side-effect and interaction profile.

• Oral iron doses of 100 to 200 mg acutely raise serum hepcidin and the increase persists for 24 hours, which is the mechanism behind spacing doses out. 1
• Fractional iron absorption on alternate-day dosing ran 40 to 50% higher than on consecutive-day dosing, and total absorption from a single 200 mg dose on alternate days was roughly twice that from 100 mg on consecutive days. 1
• In a randomized controlled trial, mean hemoglobin rose 1.05 g/dL on alternate-day iron against 1.36 g/dL on daily iron, a difference that was not statistically significant, while nausea was reported more often in the alternate-day arm at week 4 (10.3% versus 2%). 2
• A consensus statement on iron in pregnancy notes that maximal fractional absorption occurred at 60 mg of elemental iron, that intermittent dosing overcomes hepcidin suppression, and that alternate-day dosing can be considered to limit side effects in obstetric iron deficiency. 3
• Iron sits at 27 mg a day for pregnancy against a 45 mg adult upper limit, high-dose supplements bring constipation, nausea, and gastric upset, ascorbic acid improves nonheme iron absorption, and calcium might interfere with it. 4

Which option makes sense?

Options in this comparison can differ substantially in suitability. Please consult your healthcare provider to interpret the evidence, limitations, and cautions before choosing an option or changing your plan.

Disclosure: Pregnancy Smart makes supplements in this category. The comparison above is written to inform, not to steer readers toward or away from our brand.