Most standard infant formula is not lactose-free. Regular cow’s milk-based formulas contain lactose as their primary carbohydrate, and manufacturers actually add extra lactose to match the concentration found in breast milk (about 7 grams per 100 mL). However, lactose-free versions do exist and are widely available for babies who need them.
Why Standard Formula Contains Lactose
Lactose is the natural sugar in all mammalian milk, including human breast milk. Cow’s milk naturally contains about 5 grams of lactose per 100 mL, which is lower than the 7 grams per 100 mL in breast milk. To close that gap, formula manufacturers add lactose to standard cow’s milk-based formulas so the carbohydrate profile more closely mirrors what a breastfed baby would receive.
Lactose also plays a functional role beyond just providing calories. Research published in the American Journal of Clinical Nutrition found that calcium absorption was significantly higher from lactose-containing formula compared to lactose-free formula, with a mean difference of about 10%. That said, calcium absorption from lactose-free formula still meets the needs of full-term infants when the formula’s calcium content is adequate. Zinc absorption showed no difference between the two types.
Lactose-Free Formulas and What’s in Them
Lactose-free infant formulas are cow’s milk-based but swap out the lactose for other carbohydrate sources. The most common replacements are glucose polymers derived from corn syrup solids. Despite the name, corn syrup solids in infant formula are not the same as high-fructose corn syrup. They’re simply chains of glucose molecules broken down from corn starch using heat and enzymes. Maltodextrin, made from corn, rice, or potato starch, is another carbohydrate frequently used in these formulas.
These substitutes provide the same energy as lactose. The protein and fat sources in lactose-free formula remain cow’s milk-based, which is an important distinction covered below.
Soy Formula Is Also Lactose-Free
All soy-based infant formulas are inherently lactose-free because they’re made from soy protein rather than cow’s milk. If your baby needs to avoid lactose, soy formula is one option, though it comes with its own considerations. The carbohydrate in soy formulas typically comes from corn-based sugars or sucrose rather than lactose.
True Lactose Intolerance in Babies Is Rare
The American Academy of Pediatrics notes that it is extremely rare for babies to have a significant problem digesting lactose. Congenital lactose intolerance, where a baby is born unable to produce the enzyme that breaks down lactose, is an uncommon genetic condition. Most lactose intolerance develops later in childhood or adulthood as the body gradually produces less of that enzyme.
What does happen more commonly is temporary, or secondary, lactose intolerance. This occurs when something damages the lining of the intestines, most often a stomach virus like rotavirus or a bout of gastroenteritis. The damaged intestinal lining temporarily can’t produce enough enzyme to handle lactose, leading to diarrhea, gas, and discomfort. According to the American College of Gastroenterology, this type of lactose intolerance typically resolves within three to four weeks as the intestinal lining heals. A pediatrician may recommend a lactose-free formula during that recovery window, then transition back to a standard formula once the gut has repaired itself.
Lactose-Free Formula Won’t Help a Milk Allergy
This is one of the most important distinctions parents need to understand. Lactose intolerance and cow’s milk protein allergy are two completely different problems. Lactose intolerance is about difficulty digesting a sugar. Cow’s milk protein allergy is an immune reaction to the proteins in cow’s milk, and it can cause colic, vomiting, failure to thrive, or even bloody diarrhea.
Lactose-free formula still contains cow’s milk proteins. If your baby has a true milk allergy, switching to a lactose-free formula won’t solve the problem because the proteins triggering the reaction are still there. These babies need a different category of formula entirely. Extensively hydrolyzed formulas, sometimes called “predigested” formulas, contain cow’s milk proteins that have been broken down into much smaller pieces the immune system is less likely to react to. In severe cases, amino acid-based formulas may be necessary.
Soy formula might seem like a logical alternative for milk-allergic babies, but up to half of infants with cow’s milk protein allergy are also sensitive to soy protein. For this reason, soy formula is generally not recommended as a first-line substitute for babies with confirmed milk allergy.
How to Tell What Your Formula Contains
The ingredient list on any formula container will tell you whether it contains lactose. If lactose is listed among the first few ingredients, the formula is a standard lactose-containing product. Formulas marketed as “lactose-free” will instead list corn syrup solids, maltodextrin, or sucrose as their carbohydrate source. Some partially hydrolyzed “gentle” formulas reduce the lactose content without eliminating it entirely, so if you need a fully lactose-free option, check that the label specifically says “lactose-free” rather than “reduced lactose” or “low lactose.”