My LO have not poo for two days.hes on fully formula. Is it ok?

Two days is still ok as our babies get constipated once a while. But if it becomes three days and above too frequent pls change his formula or give more water. My gal used to be on enfamil and she has bad constipation like once every four days and it resulted in her getting uti. I switched her to nan and now she pops almost everyday