First of all, talk to your pediatrician. She or he will have your child"s past height and weight recorded on a growth curve. Your pediatrician will likely ask you to bring your child in for a weight check in the office. All scales are different and your home scale may not be calibrated like the clinic scale.
If your child has lost weight or is not gaining as expected, your pediatrician will obtain a three-day diet history. You"ll write down what your child eats for three days and your pediatrician will calculate the calorie intake. If the calories are not sufficient for growth your doctor may recommend a nutritional supplement such as PediaSure. For a breastfed infant, you may need to work with a lactation nurse. For formula-fed babies, your pediatrician would want to know how many bottles your baby drinks over 24 hours on average.
Some children are picky eaters. Occasionally, a child may be so picky that she or he fails to gain weight. When this occurs, it"s usually best to continue offering the child diverse foods while working with a pediatrician on a plan to ensure the child is getting enough calories and nutrients.
Dr. Megan Baker, a pediatrician at Vancouver Clinic, discusses what to do if your child is not gaining weight.Quoted From: https://tvc.org/news/child-not-gaining-weight/