What damage can mild anemia do in the body?

Low oxygen: Mild to moderate anemia results in fatigue and inefficient organ function due to low oxygen (poor mental function, muscle cramping, poor kidney function, etc). Severe anemia, especially in the context of other diseases like heart disease, can lead to such inefficient energy use that organs fail (heart attack, heart failure, stroke, etc)

Find the cause: Mild anemia is most concerning as a marker for underlying illness. Especially, in a young woman whose anemia is due to iron deficiency but for whom diet and monthly loss are not the key, it's a warning of cancer or stomach ulcer until proved otherwise. A full workup is a basic right here.