How do you know when your anemic, or can being anemic cause you to become tired or hard to breath?

Anemia symptoms. Anemia causes low hemoglobin and low oxygenation state leading to hypoxia driven symptoms such as fatigue, shortness of breath, dizziness, angina, chest pain, palpitations, headaches, decreased exercise tolerance, memory and balance problems, pica symptoms, symptoms related to occult or obvious bleeding.
Blood test. A simple blood test can show if you are anemic, and yes anemia can cause you to feel tired and short of breath, but so can many other conditions.