Anemia and DGS

My son has low hemoglobin. I think this has always been a problem, but in the past there has always been a reason why his hemoglogin could be low. Normal to dip down after birth, surgeries, chronic disease. He is “healthy” now, and it has dipped down again. Iron suplemnt brings him back up , but from the bloodwork, his iron isn’t low?

Anybody have experience with something like this?

Thanks!