Formula & Diarrhea

Babies normally have soft -- sometimes runny -- bowel movements, especially if they are breast fed. If the baby is drinking formula and develops diarrhea, his parents may wonder if the formula is causing the problem. The doctor can help the parents pinpoint the cause of diarrhea and prescribe a change in formula.

Bowel Habit Changes

Parents of a formula-fed baby who develops diarrhea can more easily tell when the bowel movement is actually diarrhea. The normal stool of a baby who drinks formula is a soft, pasty consistency and the color ranges from gray-green to brown. The baby’s daily bowel movement -- or BM -- habits also range from one or two BMs a day to one every day or two, writes the BabyCareAdvice website.

Runny bowel movements in a formula-fed baby are still normal, especially if the child is thriving and gaining weight.


Baby drinking milk while lying on counter

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If your baby is breast fed and you try to supplement with formula, he could develop mild diarrhea. Baby formula is made from cow’s milk and the baby may be intolerant to one of the milk proteins. It is rare that a baby is lactose intolerant before the age of 2, states Dr. Alan Greene in an article in "Parents" magazine.

If the baby has problems with regular formula, he may do well on soy formula. About 20 percent of babies also have problems tolerating soy formula. These children do handle milk well as they get older.

Milk Allergy/Intolerance

Babies can develop milk allergies because of the immaturity of their immune and digestive systems. These children may experience symptoms such as:

  • abdominal bloating
  • excessive gas
  • cramping
  • diarrhea
  • blood or mucus in the stool
  • vomiting
  • failure to gain weight or weight loss

Lactose Overload

Baby drinking milk while lying on counter

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“Functional lactase deficiency,” or lactose overload, develops when very young babies do not digest all the lactose that is contained in large amounts of formula. If the baby’s parents are giving him too much formula -- and thus overfeeding him -- lactose overload can be the result. Symptoms include frequent, watery bowel movements that may be green. The odor of these movements may be slightly or very offensive. The BMs can be frothy or explosive. The baby can develop cramps and bloating, suffer from excessive gas, and be irritable and sleepless. He may also seem to be hungry all the time and gain weight quickly. This may occur when the baby is less than 3 months to about 5 months old.

Soy-Based Formula

If the baby develops diarrhea and he is drinking a regular formula, a temporary switch to a soy-based formula may help him. If the soy formula contains fiber, this can help to slow the baby’s bowels down. Oral rehydration solution in between formula feedings helps keep the baby hydrated.