Low hemoglobin levels can cause anemia, which can lead to fatigue, weakness, and shortness of breath. This happens when your body doesn't have enough healthy red blood cells or hemoglobin to carry oxygen to your organs and tissues. Symptoms *Extreme tiredness *Fast or irregular heartbeat *Chest pain *Shortness of breath *Dizziness or lightheadedness *Swelling in the hands or feet *Pale skin, nail beds, mouth, or gums *Brittle, cracked, or spoon-shaped nails *Hair loss *Cracks near the side of yo