Can formula go back in the fridge after being heated?

In this brief article, we will answer, “ can formula go back in the fridge after being heated?”. We will also discuss the safety measurements when handling baby formula and the shelf life of baby formula.

Can formula go back in the fridge after being heated?

No, a formula can not go back in the fridge after being heated or reaching room temperature; this is because baby formula is a milk-based product, meaning it is loaded with nutrients. 

Bacteria grow on nutritional substrates like milk and increase in number when left in a warm environment, meaning formula can be harmful to your baby if it is left after being mixed.

How long does formula milk last once mixed?

You can keep unused Baby formula milk in the fridge for 3 to 4 hours, and you can store it in the freezer for 24 hours; however, it is not recommended as the product components will separate.

How long can you keep baby formula at room temperature?

Generally, the baby formula lasts from 1 to 2 hours if you do not heat it and leave it covered; however, this differs from one brand to another. Always check the label instruction to know how long you can keep it at room temperature.

For the best baby formula brands, click here.

Why is it not advisable to keep baby formula at room temperature for more than 2 hours?

We will get a bit scientific here. The reason why you can not keep baby formula at room temperature for more than 2 hours is related to the life cycle of bacteria.

In general, the life cycle of bacteria is 24 hours, divided into 4 phases: the lag phase, log phase, stationary phase, and death phase.

When bacteria find a nutritional substrate, they start to exploit it for its reproduction. The first phase in the bacteria’s life cycle is known as the lag phase; this lasts for 1 hour or more depending on the bacterial strain. The bacteria prepares itself for growth in the lag phase, but cell reproduction does not start yet.

After an hour, the log phase starts. In this phase, bacteria divide and grow in number exponentially, and warm temperature only aids in the cell doubling; this means after two hours, your baby’s formula is filled with a countless number of bacterial cells.

Refrigerating heated baby formula will not stop bacterial growth; instead, it slows it for a while. This means there is still danger in feeding your refrigerated formula to your baby.

Why should you not feed your baby leftover baby formula?

This is because the human body contains natural beneficial microbes known as microflora. While feeding your baby, the microflora in its mouth contaminates the formula.

Feeding your baby used formula risks their chances of being infected. The American Academy of Pediatrics (AAP) advises parents to dispose of used formulas.

How to prepare and store formula milk?

Water for baby formula

Never use tap water unless you have sterilized it. This is because tap water can be contaminated with bacteria and has additives harmful to the baby. Instead, use distilled or bottled water because they are clean and free of possible contaminants like lead, pesticides, bacteria, fungal spores, nitrates, and more.

Preparing bottles

Each brand had its instructions on how to prepare baby formula. As a general rule, mix the specified amount of formula written on the label with water.

Adding too much water will dilute the formula, giving your baby fewer nutrients than required. On the other hand, adding too much formula can cause dehydration and constipation to your baby.

Breastfeeding vs. formula feeding, which is better?

The American Academy of Pediatrics (AAP), the American Medical Association (AMA), and the World Health Organization (WHO) recommend breastfeeding as the best choice for babies. Besides bonding with your child, breastfeeding comes with lower risks than formula. 

Breastfed babies are not as commonly infected as formula-fed infants. This is because breastfeeding passes antibodies formed in the mother’s body to the baby, improving the baby’s immune system.

Breastfeeding lowers the chances of many infections and diseases like diarrhea, allergies, diabetes, and ear infections.

However, breastfeeding your child is not as convenient as formula feeding. Breastfeeding is not as flexible as formula feeding, and it limits the mother’s diet. Science of what they eat can be passed to the child.

How to safely store baby formula?

You should store unopened infant formula containers in a cool, dry place to ensure it remains safe for consumption. Opened infant formula containers last up to a month, but make sure to check the expiry date on the label when the container is opened.

Do not refrigerate opened baby formula; this is going to alter the chemical structure of its components, decreasing nutrients in it. 

Tightly secure the lid of the formula container so as not to expose it to air. This will cause oxidation and contamination making it unsafe for consumption.

The bottomline

Baby formula is a convenient nutritional alternative to breastfeeding; however, you should treat it with caution as it can harm your baby. You should not refrigerate or reuse baby formula to not risk infection in your child.


In this brief article, we answered, “ can formula go back in the fridge after being heated?”. We have also discussed safety measurements when handling baby formula and the shelf life of baby formula.


Hi, I am Charlotte, I love cooking and in my previous life, I was a chef. I bring some of my experience to the recipes on this hub and answer your food questions.