His weight is on the 25th percentile and his height is on the 75th percentile for his age. Were there any other labs that were also low? There can be numerous reasons why the hemoglobin is below normal. If his MD suspects it is anemia, then they should do an Iron profile blood work to determine the type of anemia and the correct treatment for it. If not, then the MD needs run tests to find out why for proper treatment.