How Many Times Can You Reheat Formula? – Formula Feeding Safety

By Maria Wilcox •  Updated: 07/12/22 •  8 min read
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How many times can you reheat formula? That’s a good question! As you may already know, reheating any type of food after time has passed comes with risks. So, when it comes to baby formula, you may be wondering if reheating formula is actually safe. 

Thankfully, we’ve got the answers you need in today’s post. So, if you’re ready, let’s go ahead and get into the details. 

reheat formula

Can You Reheat Formula?

You can reheat a bottle of freshly made formula only if no longer than an hour goes by after you’ve made it up. 

After one hour at room temperature, you’ll need to refrigerate the unused bottle. Or if used, discard the baby formula as there is a chance that bacterial growth may have already begun and thus, poses a risk to your baby’s health. 

When reheating your baby’s bottle, make sure that you do so in a way that is in accordance with safe reheating procedures

We don’t recommend microwaving your baby’s bottle because it can lead to an uneven distribution of heat, which in turn, can cause the milk to be too hot in some areas and not hot enough in others. This imbalance of heat may burn your baby’s mouth.

Therefore, though microwaving is very convenient, we don’t recommend it. 

Can You Reheat Formula Multiple Times?

You should not reheat your baby’s bottle multiple times. 

By reheating your baby’s bottle more than once, you are encouraging an environment within the bottle that can cause bacteria to flourish. This is especially true if you are reheating your baby’s bottle multiple times after it has been refrigerated. 

It is for these reasons that we recommend that you reheat your baby’s bottle only once, and even then, the formula should’ve been freshly made no more than an hour ago, should not have been refrigerated at any point, and should be unused (no leftovers). 

Can I Reheat Untouched Formula?

Yes, it is safe to reheat untouched formula. By “untouched” we simply mean that the baby has not yet consumed the bottle and that the bottle has not yet been in your baby’s mouth.

If your baby has already consumed the bottle or if the bottle has been in your baby’s mouth, you may not reheat the bottle, nor should you refrigerate the bottle. Instead, you should have your baby drink his or her bottle within one hour of it having been made up. Otherwise, you will need to discard the formula. 

Dr. Brown's Natural Flow Anti-Colic Baby Bottle - 4oz - 4pk

Can You Refrigerate Formula After Warming It?

Unfortunately, opinions about whether or not you should refrigerate formula after warming it are split. 

Many moms claim that they have done this time and time again, but the experts state that doing so is risky

One reason that refrigerating formula after warming may pose a risk to your baby is that the rapid heat up and cool down process of warming and then refrigerating formula may encourage bacterial growth. 

Bacterial growth in your baby’s bottle can eventually lead to sickness, or at the very least, a severe tummy ache or a bit of diarrhea. Either way, you want to keep your baby’s formula as clean and as safe as possible. Unfortunately, refrigerating a bottle that has already been warmed may pose unintended risks to your little one. 

If you must refrigerate your baby’s bottle after warming it, be sure only to do so with a bottle that hasn’t been partially consumed. If the bottle has entered your baby’s mouth, any leftovers cannot safely be reused at another time, even if refrigerated. 

How Long Can You Keep Formula Once Made Up?

Can You Reheat Formula Within an Hour?

Once a baby’s bottle is made up, your baby must consume it within an hour’s span. After that, your baby’s bottle is no longer deemed safe to drink. 

To prevent spoilage and waste, consider refrigerating your baby’s bottle after an hour’s time, but only if it has not been partially consumed.

How Long Is Formula Good For Once Reheated?

Baby formula is only good for one hour whether it is made up fresh or has been reheated. After this period of time, you will need to toss any reheated formula.

The reason that we recommend tossing the formula that has been reheated after an hour is that germs and bacteria can develop if your formula sits for longer than this.

If your milk is fresh and hadn’t previously been reheated, you can safely store your milk in the refrigerator to be reheated only once. Remember that once your formula has been in the fridge, it cannot be refrigerated again after it has been reheated (or partially consumed).

Although all of this may sound technical, complicated, and maybe even a little frustrating, the truth is that by following these protocols you are lowering the risks of your baby getting sick from coming in contact with various types of bacteria and germs.

Baby Bottle Warmer 2-in-1 Bottle Warmer for Breastmilk or Formula One Button Control Easy to Use with Water Vial

Why Is It Bad to Reheat Formula? Why Can’t You Reheat Formula?

Reheating formula isn’t inherently bad, but it can be under a few circumstances. 

Reheating formula is only risky when the formula has been sitting out for more than one hour, has been partially consumed by your baby, or when it is reheated multiple times after having been refrigerated. 

Other than that, reheating baby formula is perfectly safe. To safely reheat your baby’s formula, do the following: 

  • Take your baby’s bottle. Place it in a bottle warmer for the amount of time directed according to your bottle warmer instructions.
  • If you don’t have a bottle warmer, take a microwave-safe bowl and fill it with water. Place the bowl of water in the microwave until the water is hot.
  • Place your baby’s bottle in the warm water to evenly heat the milk. Remove the bottle from the water. Test it on your wrist to ensure that the milk is at the temperature desired. 
  • You can also warm your baby’s bottle using a similar method. Heat water in a small pot over the stove. Immerse your baby’s bottle in the hot water until the bottle is warmed. Do not boil the bottle in the water. Simply wait for the water to heat, shut off the stove, and then immerse the bottle in the water. 

Note: Remember that it isn’t advised that you warm your baby’s bottle directly in the microwave. Doing so may cause hot pockets to form within the milk and can scorch your baby’s mouth.

What Happens If You Reheat Formula?

If you reheat the formula under the proper circumstances, nothing negative should happen as a result of having warmed it.

However, if you reheat a bottle that may have been introduced to bacteria in the ways previously mentioned, then there is the potential that your baby may become ill from having consumed infected milk. 

Signs and symptoms that your baby may have been exposed to bacteria in his or her milk bottle include:

baby formula

Reheating Formula: Pay Close Attention…

Remember that when reheating formula, certain guidelines must be considered in order to keep the process safe. 

When attempting to reheat formula, make sure that the formula is fresh. It must not have been partially consumed by your baby. You also always want to ensure that the formula has not been left out at room temperature for over an hour.

Bear in mind that formula doesn’t need to be warmed before giving it to your little one. So, even though you may not reheat a bottle that has been partially consumed, you may still continue feeding it to your little one until one hour is up.

We hope that helps clear things up a bit. Thanks for stopping by!


Baby didn’t finish bottle of formula – Can I reuse?

Always discard any leftovers and make up a fresh bottle for your baby in order to best keep him or her safe and healthy.

Maria Wilcox

Former instructor with an M.A. in Education turned grateful stay-at-home mama to one, I look to share helpful insights related to babies, toddlers, kids, and families for the benefit of real people just like you.

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