Formula and Constipation

My 5-month-old has been on formula with iron since she was 3 months old. She has been constipated since. Should I switch to something with less iron? My doctor suggested Nutramigen, but I was thinking of trying Carnation Good Start.

Baby taking milk from a bottle. Formula and Constipation

Dr. Greene’s Answer:

First, let’s address the iron in formula and constipation question. Some people will (or have) told you that the iron is the problem and that switching to a low-iron formula will help. It makes sense, because when adults take iron supplements, we get constipated as a side effect. But there was a study done concerning the formula and constipation question in babies. Half got low iron, half got regular–not knowing which was which–and the rate of constipation was the same in both groups. For most kids that does not make a difference, and the iron is very important for growing babies.

The constipation can be formula-related, though. Allergies to some of the proteins in the formula could cause the discomfort. Sometimes switching to another brand will help (the milk-based formulas are not all the same). Sometimes switching to soy will help. All other things being equal, soy makes stools firmer–but for kids with an isolated allergy to milk protein, the constipation may dramatically clear up on soy.

Still, about 20 percent of kids with a cow’s milk protein allergy will also have a soy allergy at that age, so if it doesn’t work you still will not know if this is formula related. Most allergies to milk and soy are outgrown as infants or toddlers.

I like your pediatrician’s suggestion of switching to Nutramigen. It is a hydrolysate formula, which means the proteins have already been chopped into building blocks so they are easier to digest and pretty impossible to be allergic to. If Nutramigen does not work, you will know that formula is not the issue.

Carnation Good Start is another good possibility. It is an example of milk-based formulas not all being the same. The milk proteins in Good Start are partially hydrolyzed, so it may be easier for some kids to digest, but it will not do the trick for a full-blown cow’s milk protein allergy.

If the formula is not the issue, there is a long list of rare causes that could be causing the constipation. Hirschsprung’s disease is probably the most important. This is where there are not enough nerve endings in the end of the colon to push stool out effectively.

Dr. Alan Greene

Dr. Greene is the founder of (cited by the AMA as “the pioneer physician Web site”), a practicing pediatrician, father of four, & author of Raising Baby Green & Feeding Baby Green. He appears frequently in the media including such venues as the The New York Times, the TODAY Show, Good Morning America, & the Dr. Oz Show.

  1. Alyson

    My 9mo old started formula approx. a month ago. Previous to that he was breastfed. Just recently we are experiencing the strain when he’s pooping, also outburst’s of screaming while going. Once it’s passed he is fine but he is in a lot of pain while going. He is eating normal foods and drinking a nice amount of water. Because of the recent switch to formula and the recent constipation I am thinking the two link? Any advice?

  2. Kelly

    My 2 week old has been on The Honest Company Organic Formula since his first feeding in the hospital, today at pediatricians office he pooped and it had a little bright red blood, she said likely a strain, track bowel movements for three days and call, dark stool call asap…. she said could be straining, his bowel movement she said looks more dense than it should, and should be more watery, but I am not breast feeding. She also said could be milk protein allergy, but too soon to tell. He has no gas, no reflux, isn’t fussy, doesn’t scream, is pooping 2 to 3 times a day, so i’m just not sure, any advise? Of course blood in stool is a scary thing, but I don’t want to over react.

  3. Miche

    My baby is 9 m.o old now. She is always experiencing constipation with her Organic milk. She cries every time she poo and is straining. She had lactose intolerance with her prev Milk at 7 months so the doctor decided to shift her to an organic milk to make the poo soft. First week was good and perfect but she experienced constipation every other day again. I cry every time she strains and cries. She is always constipated. What should I do? Please help. Thank you.

  4. Harminder brar

    My 30month daughter is constipated after she started cows milk. Now I give her enfagrow but still she poo after two days. Poo is hard and like pebbles, some times small balls. Also she is not eating fruits….very fussy for eating. Water intake is good. Please give me some suggestions. Thanks


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