How Long Is a Formula Bottle Good for?

Let’s face it: Formula isn’t cheap. But baby doesn’t always chug a bottle in one sitting (and might even conk out while you’re preparing one). You hate to waste formula—but you also want to make sure you’re being safe. At this point, you might ask: How long is a formula bottle good for, exactly?

“The scenario: Husband gets up at midnight to make the bottles,” says Mandy Ellsworth, a community member on The Bump. “He pours the ready-to-eat formula in the bottles, heats some water, then places the bottles in the water to warm up. Then, Mommy, Daddy and two crying babies all manage to fall asleep before we feed the babies, and we wake up at 2:40 a.m. Bottles have cooled off by now. This formula is bad, right?” (Spoiler alert: Unfortunately, yes.)

Like all food and drink, formula has a shelf life, which gets shorter after it’s been heated and prepared. But the amount of time a formula bottle is good for changes based on whether baby has had a sip, along with a slew of other factors. “You want to prevent bacteria that can make baby sick or cause the formula to spoil from growing,” explains Ellen Shumaker, PhD, a food safety expert and director of outreach for the Safe Plates program at North Carolina State University.

So, how long is formula good for once mixed? If you’re supplementing with formula, here’s what you need to know about the shelf life of that middle-of-the-night bottle—straight from experts.

Key Takeaways

• The rule of thumb for formula is: You should use a bottle within two hours of preparing it. Once baby starts feeding, you have one hour before you should throw it out.
• The same rule applies if you’ve warmed up your bottle of formula.
• Once you’ve mixed a bottle of formula, it can stay good in the fridge for 24 hours (if baby hasn’t taken a sip from it). Experts advise making smaller bottles to avoid wasting formula.

How Long Is Formula Good for Once Mixed?

So how long is a bottle of formula good for? The Centers for Disease Control and Prevention (CDC) says you should use a bottle of formula within two hours of preparing it and one hour after baby starts feeding. But there are a few nuances to consider—see ahead for what pediatricians recommend in various circumstances.

At room temperature

If you prep a bottle of formula and leave it at room temperature, baby should start drinking it within two hours. After they begin feeding, they have one hour to finish. “The key is there can be bacteria in baby’s saliva and, once that mixes with the milk in the bottle, our little chemistry experiment has begun,” says Ashanti Woods, MD, a pediatrician at Baltimore’s Mercy Medical Center. “When the formula is simply prepared, there’s presumably no bacteria in the milk and we therefore have a longer time—two hours—to begin drinking.”

Warmed up

The rules for a warmed-up bottle are the same as they are for a room temperature bottle, says Shumaker. Meaning, if baby’s started drinking a warmed-up bottle, it should be consumed within an hour. If it sits and baby hasn’t taken a sip, you have two hours.

In the refrigerator

It happens: You make a bottle, but baby falls asleep. Luckily, you have more time with a refrigerated bottle—provided baby doesn’t take a drink first. “Once a bottle of formula’s mixed, it can safely be stored in the fridge for up to 24 hours,” Shumaker says.

How Long Is a Partially Used Formula Bottle Good for?

Again, once baby has started drinking from a bottle, it’s only good for an hour, says Rebecca S. Fisk, MD, a pediatric hospitalist at Northwell’s Lenox Hill Hospital in New York City. “Once baby drinks from a bottle, the saliva from baby’s mouth can be in the formula,” she says. “You don’t want bacteria to grow in that formula, populate and be fed back to baby.”

To save precious formula, Fisk recommends splitting it into smaller bottles. “There’s a little more work involved, but smaller is better—there’s less waste,” she says.

To Sum It Up

It’s understandable to want to get the most out of your bottle of formula, but doctors stress the importance of following safety rules with your little one. “Infants are considered a susceptible population given that their immune systems are not fully developed. In general, food safety recommendations are very conservative for infants because of that,” Shumaker says.

A good rule of thumb is to get rid of the bottle if it’s been two hours since it was prepared, and after an hour if baby already took a sip. It’ll stay good in the refrigerator for 24 hours, provided baby didn’t start drinking from it. If you’re unsure how long a bottle’s been sitting out, it’s best to get rid of it. “When in doubt, throw it out,” Fisk says.

Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.