Well, obviously talk to your pediatrician about this but my kids' pediatrician has had us supplementing since my kids were babies. She told me I was probably vitamin D deficient therefore my milk didn't have enough. She actually sees kids with rickets in my area (Michigan). I give my under 100 pound kids 2000 iu a day and my over 100 kid 5000 iu a day (that's what my husband and I take as well now).