M.S.
Give it to him when you want to. My little one had cereal added to her bottles around six to eight weeks old for reflux. She did well with it and had no problems. So if your little guy is hungry adding cereal may help. He should do fine. You can always ask your doctor as well. He could tell you the right amount to add. I think my doctor told me to add one tablespoon for every two ounces. It has been awhile my daughter is fixing to be a year old. His bm's might get a little hard at first but once he is use to the cereal it should go away. I would also just watch for signs like fussiness or gas. When adding cereal it could give him a tummy ache. If it does I wouldn't use it anymore until he is older. My daughter did fine but each baby will be different. I would go by your motherly instincts, if you feel it is right then try it but if you have doubts don't try it or call your peditrician and get his opinion.