Iron deficiency is the most common nutritional deficiency worldwide. But iron supplements have a reputation for causing constipation, nausea, and stomach pain. The good news: form matters, and gentler options exist.
Iron Forms Compared
Ferrous bisglycinate (Gentle Iron) - Best tolerated - Good absorption - Less constipation - More expensive
Ferrous sulfate - Cheapest - Reasonable absorption - Most GI side effects - Common in prescriptions
Ferrous gluconate - Lower iron content per pill - Slightly gentler than sulfate - May need more pills
Carbonyl iron - Very slow release - Fewer acute side effects - Lower risk of accidental overdose
Heme iron polypeptide - From animal sources - Absorbs independently of food - Premium price
Where to Find Iron
Standalone iron - Best for treating deficiency - Wide range of doses (18-65mg) - Choose bisglycinate for gentleness
Prenatal vitamins - Essential, should contain 27-30mg - Check the form. Many use ferrous fumarate.
Some multivitamins - Often 8-18mg - Many adult multivitamins skip iron (men rarely need it) - Women's formulas usually include it
Blood builder formulas - Combined with B12, folate, vitamin C - Good for comprehensive deficiency support - Vitamin C significantly improves absorption
Critical: Test Before Supplementing
Iron is one of the few supplements where too much is dangerous.
Always get tested first: - Ferritin (storage iron) - should be 50-150 ng/mL - Hemoglobin and CBC
Who needs iron: - Women with heavy periods - Pregnant women - Vegetarians/vegans - Endurance athletes - Those with diagnosed deficiency
Who should NOT supplement without testing: - Men (rarely deficient) - Postmenopausal women - Those with hemochromatosis - Anyone without confirmed deficiency