Iron bisglycinate (chelated form) absorbs excellently and causes the fewest digestive side effects. Heme iron from animal sources absorbs 2-3 times better than plant-based iron. Iron fumarate and sulfate are cheaper but more often cause constipation and nausea.

Vitamin C converts plant-based iron into a better-absorbed form. Just one orange (75 mg vitamin C) increases iron absorption up to threefold. Take iron with vitamin C-rich food or a supplement. At the same time, avoid tea and coffee when taking iron, as tannins inhibit absorption.

Yes, iron overdose is dangerous because the body cannot actively excrete excess iron. Accumulation damages the liver, heart, and pancreas. Do not take iron supplements without a blood test — check ferritin and hemoglobin levels first. This is especially important for men and post-menopausal women.

Coffee, tea, milk, and calcium-rich foods significantly inhibit iron absorption. Tannins in tea and coffee reduce absorption by up to 60%. Phytates in whole grains and oxalates in spinach also bind iron. Leave at least two hours between these products and your iron supplement.