There are many factors to consider when deciding if a child is truly underweight. First of all, if there are any underlying medical conditions, those must be considered. Second, genetics plays a major role. If both parents are very thin, the child will more than likely be thin as well. And third, if the child has recently gone through a major growth spurt, they may have thinned out, which is normal. Their body weight will probably catch up to their height soon enough.
If you feel that your child is too thin and needs medical help, see a doctor. They will evaluate your child’s weight by considering the above mentioned factors as well as their place on the standard growth chart. To make this determination, a child’s body mass index (BMI) will be calculated. If your child’s BMI is below the 5th percentile on the growth chart, they are considered underweight.
A doctor may then run tests to make sure that there are no medical problems causing the weight problem. Once they have determined that your child is healthy, they will more than likely have you see a dietician who can direct you on how to properly feed your child to allow them to gain weight the proper way.