Iron bisglycinate is iron chelated to two glycine molecules. Absorbed via amino acid transporters rather than the standard non-heme iron pathway, reducing GI side effects.
Mechanism — Higher bioavailability than ferrous sulfate at lower doses. Less free iron in the gut means less constipation, nausea, and oxidative damage to enterocytes.
Use case — Iron-deficiency anemia, low ferritin without anemia, heavy menstrual losses. Typical 25-50 mg elemental iron daily, on empty stomach with vitamin C, away from coffee, calcium, and tea.
Caveats — Don't supplement iron without a ferritin level. Men rarely need it; hemochromatosis is real. Recheck ferritin after 8-12 weeks to titrate.