Testing for lactose intolerance in a toddler may depend on your pediatrician’s preference. Some may diagnose the lactose intolerance based on symptoms alone, and more specifically if those symptoms improve when you remove dairy from your toddler’s diet, while others may request that your toddler have some testing done.
For example, the American Academy of Pediatrics explains that noninvasive hydrogen breath testing or an invasive intestinal biopsy can help definitively diagnose lactose intolerance.2
2. American Academy of Pediatrics. Lactose Intolerance in Infants & Children: Parent FAQs. HealthyChildren.org.