My one year old daughter is had only gained 500g in 2 months. from the time she was born she had been struggling to gain weight. ?

Basics: Poor weight gain is often the result of inadequate intake, increased utilization or loss of ingested calories through the gut. Only a review of the patient history, exam, testing & sometimes feeding in a controlled setting can sort out the cause. There are mechanical, metabolic, & other causes that require careful evaluation to reveal a cause & treatment.