Scott Keatley, RD, co-owner of Keatley Medical Nutrition Therapy, explains that iron supplements are essential for producing hemoglobin, the protein in red blood cells that carries oxygen throughout the body. He notes that iron pills typically start improving energy levels within a few weeks, but full iron restoration can take several months. For best absorption, he recommends taking iron pills with vitamin C and avoiding taking them with calcium. Scott also highlights potential side effects like nausea and constipation and advises consulting a healthcare provider if symptoms persist after a few months or if side effects become severe.