Anubha,
I agree with Canadian Family, your child needs hypertransfusion - maintaining a hemoglobin above 9.5 will normalize your child's hemoglobin. It takes several transfusions to build up the hemoglobin, if your child's starting point was 5, the transfusion may have brought it to 8.5 or 9 - if you repeat the transfusion 1 week later your child's hemoglobin level will build to be above 10.
If your child has had a low hemoglobin for many years the spleen may also be big, it will take time for hypertransfusions to shrink the spleen. An enlarged spleen breaks down red blood cells at a quicker rate.
Low appetite is generally associated with low hemoglobin, but as Canadian_Family has said only a blood test can give an accurate picture of your child's levels.
Best of luck,
Sharmin