Is it safe to add cereal to your baby's bottle when they are 4 months old?

Safe?: Yes it's safe but it's usually not useful in any way. Most of us try it to make the baby "full" so they will sleep longer (I tried with a couple of my kids). It doesn't really help and it clogs up the bottle nipple.

Yes but why ?: If the kid has reflux we do it all the time, since thicker feeds stay down better.If it's to start cereal, it should be done on a spoon and as a texture thing. Adding solids is a training exercise and not really necessary that young. If you want to train baby to eat at the table you don't use a bottle.It has never been shown to make babies sleep better/longer.