Yes, both chemotherapy and radiation treatment can cause anemia, which in turn can lower the amount of hemoglobin in your father's blood. Low hemoglobin causes fatigue and shortness of breath
It may take several weeks after treatment for your father's blood counts to return to normal, and during this time his doctor may take a wait-and-see attitude. As a caregiver, there's not a lot you can do to boost hemoglobin, but make sure your dad's eating high protein meals and drinking plenty of fluids to keep his strength up. Focus particularly on foods rich in iron, like green leafy vegetables, egg yolks, and iron-fortified whole-grain cereal. Folic acid also helps combat anemia, so offer your dad foods high in folic acid, such as oatmeal and peanut butter. It might also help your dad to take iron and folic acid supplements, but ask his doctor before he starts trying them.
It's important to call his doctor or nurse regularly and discuss your father's symptoms. Keep track of his activity level and whether it's improving or worsening. Watch for shortness of breath and chest pain, particularly when your father isn't exerting himself, and for any signs of dizziness or confusion. Also try to get your father to limit his activities to mornings -- or whenever he feels most energetic -- and to get plenty of rest when he's tired. If your father's doctor decides that his hemoglobin count is too low, there are supportive medications that can help boost the red blood cell count. A blood transfusion is another treatment available to combat anemia.
because there are too few red blood cells to circulate oxygen to the tissues, making your father's body feel like it's hard to move. It's the same feeling you may have experienced at very high altitude.