When a friend of mine had her baby a few months ago, she was still living with her parents. In general, the setup worked great for the time being, and the grandmother loved the idea of being the built-in babysitter temporarily. However, one subject that always caused disagreement in the house when I was there was whether or not they should refrigerate the baby’s leftover formula. While the grandparents thought that frugality and saving should be prioritized, my friend was extremely cautious and threw out any formula that was out of the fridge at all. I researched the health standards that experts agree on for formula, and it turns out my friend had the right idea. However, there are some instances when formula can be refrigerated and saved.

As a new mom, you’re trying to save money in any way that you can. Throwing out expensive formula feels wrong, but you should always put your baby’s health first. Studies show that letting pre-made formula sit at room temperature for two hours or more can cause dangerous bacteria to breed in the liquid. So, if you’re feeding your baby and he or she isn’t hungry right away, go ahead and put it back in the refrigerator until it’s time to eat again. If you’re feeding your baby and he or she drinks formula on and off for an hour or so and there is some leftover, it’s best to dispose of the leftovers. Of course, each type of formula will have different refrigeration guidelines, so it’s good to use this as a general rule but also check it against the instructions on the bottle.

Adults have much stronger immune systems than newborns, so what seems like a minor hazard to us could actually be a hospital trip for a baby. A baby’s developing system simply cannot process even small quantities of bacteria, so a bottle that accumulates bacteria while unrefrigerated is particularly dangerous.

If you’re trying to be frugal, try mixing your own formula and refrigerating that for the recommended amount of time. Otherwise, when it comes to leftover formula, skip the frugality and prioritize your baby’s safety. Though saving money is important in your baby’s first few and expensive years of life, saving leftover formula might not be the best way to do so. By bending the rules of refrigeration on baby formula, you could make your baby seriously ill.

Source: Mary E Hancock et al: What Nurses Need to Teach Parents Who Choose to Formula-Feed Volume 14 Issue 4 pp. 302-309 September 2010