1. Take her measurements
To determine whether your child is drinking too much or too little fluid, you need to know approximately how much she requires per day. Figuring it out usually involves serious math; fortunately, Susan Baker, M.D., Ph.D., a Buffalo-based chairwoman of the AAP's committee on nutrition, has done all the work for you. Check out the chart below, designed for a healthy child in room-temperature conditions. Tack on an extra two to three ounces of fluid for every hour a toddler spends playing outdoors in warm weather; for older kids, add about four to six ounces. If your child is running a fever or has medical problems, consult your pediatrician to calculate her fluid requirement.