So, you’ve done the hard work of choosing the best formula for your baby (bravo!)…but that was just the first step in your feeding journey. And now, you’re probably finding that your laundry list of feeding questions continues to grow: Now that you’ve brought those formula canisters home, where do you put them? How do you mix formula? Maybe your baby chugged 3 ounces of formula, but left an ounce in the bottle. Should you save it for later? 

It’s a lot to digest! That’s why we’re here to guide you through all of your questions about storing and preparing formula…in a way that goes down easy.

Different Types of Baby Formula

Before we start throwing around “formula” we should define what we’re talking about. Formula is no monolith! It actually comes in three different forms—and each type has its own storage and preparation guidelines. The three types of formula are: powdered, concentrate, and ready-to-use. Here’s the scoop on each one…

  • Powdered formula is the most common and inexpensive type of formula. It comes with a pre-measured scoop you can use to mix the powder with water safely.  

  • Concentrate formula comes in liquid form, mixes with water in equal parts, and tends to cost more than powdered formula.
  • Ready-to-use (RTU) formula can be pricey because the formula is ready for baby to drink as is. It often comes in multiple packs starting at two ounces per bottle.

How to Store Baby Formula

Where do I store formula cans?

Store powdered or concentrate formula in a cool, dry area. Close contact with heat can weaken the formula’s nutrients, so it’s essential to avoid leaving formula in the car, especially on hot days. Unopened RTU formula should remain at room temperature. Opened RTU formula is okay to refrigerate and save for later—as long as your tiny feeder hasn’t started sipping on it yet. 

Which can of formula should I open first?

Choose the formula that’s the closest to expiring. In other words, “use by” dates—typically printed on the packaging—are your friend. Not only will they keep you from giving your baby expired formula, but they also tell you which container to open first. 

How long is a can of formula good for?

After opening, many formula manufacturers say to use powdered formula cans within one month. Since the average baby-parent tends to have a lot on their mind, use this pro tip: Keep a permanent marker nearby so you can label each formula container with the date you first opened it. Once a month lapses, it’s gotta go.

Concentrate and ready-to-use formulas have a shorter shelf life. They often require refrigeration and should not be stored after they’re opened. Take a gander at the “how long does formula last?” section below for more details on how long to keep concentrate and RTU formula.

How long is formula good for?

Leaving formula out for too long—especially after your little one has already started drinking it—can introduce potentially harmful bacteria into your sweet baby’s bottle. That’s why it’s important to chuck formula that’s past its prime. Here’s a quick guide to how long formula is good for….

How long does a bottle of formula last at room temperature?

One to two hours. Use powdered, concentrate, or ready-to-use within two hours of preparation, but one hour from the start of the feeding. That means if you make a bottle at 7am and leave it at room temperature, it’s good until 9am. But if your sweet babe starts eating it at 7am, then the bottle is only safe to offer until 8am. 

How long does leftover formula stay good in the bottle?

It doesn’t! Bacteria from your baby’s saliva contaminates their formula. The bacteria can grow and render the formula unsafe so it’s best to always discard formula that’s leftover after a feeding.

How long is formula good for in the fridge?

Depending on the formula, 24 to 48 hours. If you’ve prepared formula that baby won’t need right away, you can safely store it in the fridge for a short stretch:

  • Powdered formula- use within 24 hours of preparation.
  • Concentrate formula- use within 48 hours of preparation.
  • Ready-to-use formula-use within 48 hours of opening.

How long is formula good for after you warm it?

If you’ve taken some stored formula from the fridge, you can rewarm it by running it under warm water or using a bottle warmer. From the start of the feeding, the milk is good for one hour. Microwaving formula is dangerous and can burn your baby’s mouth, so stick to safe measures of warming your babe’s milk for a more comfortable feeding.

How long does formula last in the freezer?

It doesn’t! Breastmilk is okay to freeze, however, formula should never be placed in a freezer.

Can I prepare formula ahead of time?

While some parents and caregivers make bottles as often as Baby eats, others prefer making formula ahead of schedule. If your baby gets hungry every three hours and usually takes 6 ounces of formula at each feeding, you may consider preparing eight bottles of formula for a 24-hour period. Of course, making fresh bottles at each feeding time is perfectly okay, too! But if Baby doesn’t guzzle all of it, just be sure to discard whatever’s left over after an hour.

How to Prepare Baby Formula

Before showcasing your mixology skills, thoroughly wash your hands with warm soap and water and ensure your baby bottle and accessories are clean.  

Unless your baby’s pediatrician instructs otherwise, follow the instructions on the back of the formula can and use the scoop provided. You can trust that this formula recipe is designed to deliver the just-right ratio of fluid and nutrients for your baby’s growth and development. Please don’t try to wing it— incorrectly mixed formula can rob your baby of the nutrition they need while giving them too much or too little fluids…potentially causing dehydration or kidney troubles.  

How do you make a bottle of formula?

A standard powdered formula recipe calls for 2 ounces of water for every one scoop of formula. To prepare 4 ounces of formula for your sweetie, add 4 ounces of water and mix two level scoops of formula. 

  • Powdered formula recipes use a 2:1 ratio of formula to water. For a 4-ounce bottle, mix four ounces of water with two scoops of formula. 
  • Concentrate formula must be mixed with water at a 1:1 ratio. So, if you’re preparing a 4-ounce bottle of formula, you’d blend 2 ounces of formula with 2 ounces of water.  
  • Ready-to-use (RTU) formula is just like it sounds—it’s ready to use and doesn’t need to be mixed (so step away from the faucet!)

Get more baby feeding tips:

About Gabrielle McPherson

Gabrielle McPherson, MS, RDN, LDN is registered dietitian in Missouri who specializes in community and pediatric nutrition. Gaby is passionate about encouraging families to eat well in simple, practical ways that are realistic...and delicious! When not working, Gaby loves cooking, baking, and making messes and memories with her sous-chef/preschooler Charlotte.

View more posts tagged, feeding

Have questions about a Happiest Baby product? Our consultants would be happy to help! Connect with us at customercare@happiestbaby.com.

Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider.