Silent Signals: Are You Tired, or Is It Iron Deficiency?

Extreme Fatigue and Physical Weakness The most common symptom of iron deficiency is a sense of extreme fatigue that does not improve with rest. This occurs because your body lacks enough iron to produce hemoglobin, the protein responsible for transporting oxygen to your tissues. When less oxygen reaches your muscles and tissues, you will constantly feel lethargic, weak, and lacking the energy required for daily activities.