How do I know if formula is making my baby constipated?

Changes in poop patterns after switching formula are quite common. While breastfed babies usually have softer, more frequent poop, formula-fed babies tend to have thicker, paste-like, and sometimes less frequent poop. To tell if this is formula-related 'hard stool' constipation, look at:

• Is baby straining? That is, does his face turn red while straining, knees pull to belly, seems uncomfortable, but stool comes out — if it's not hard — this might be 'dyschezia,' where babies simply haven't learned to coordinate their abdominal muscles yet, not constipation.
• What's the consistency? If stool is hard, dry, ball-like, or pebble-like, that's constipation. Formula's iron or protein structure can cause this in some babies.
• How long has he been on this formula? Typically the digestive system tries to adapt in the first 3-5 days after switching.
• Are you mixing the formula correctly? Too much powder, too little water leads directly to constipation.

If stool is hard and your baby is visibly struggling and crying while passing it, and this lasts longer than a week, talk to your pediatrician about possibly trying a different formula brand (though I don't recommend brands — your doctor will suggest criteria) or adding puree supplementation. But if there's no constipation and your baby is growing well, the formula change doesn't need to be made.