How Long Is Formula Good For?

Updated Jan 21, 2026

Using baby formula for the first time often comes with plenty of new questions—how to prepare bottles, how to pick the right formula, and beyond. From mixing to everyday use, understanding the basics helps parents feel confident about keeping their baby’s feedings safe and nourishing.

Knowing how to store and properly handle baby formula is key to keeping your little one healthy. But with so many rules around fridge time, heating, and more, it can get confusing. This article breaks down everything you need to know about the question: how long is formula good for?

How Long Does Formula Last?

One of the most common questions parents have is how long infant formula stays safe to use. The answer depends on whether the formula is prepared, sitting at room temperature, or stored in the refrigerator.

How Long Can Formula Last in the Fridge?

Prepared formula—that is, once mixed—should be chilled within two hours and can safely remain in the refrigerator for up to 24 hours. After that point, bacteria can begin to grow, and the container should be discarded. Labeling refrigerated bottles with the time they were made can help you keep track and ensure your baby always gets a safe, fresh feed.

How Long Can Formula Sit Out At Room Temperature?

Prepared formula can safely sit at room temperature for up to 2 hours before growth of harmful bacteria becomes a risk. If your baby has started feeding from the bottle, it’s best to discard it after 1 hour of sitting out to avoid bacterial contamination from saliva. Unopened formula containers remain shelf-stable until the printed “use by” or expiration date—so keep them stored in a cool, dry place and check the label.

Safety Tips for Storing and Preparing Baby Formula

When it comes to baby and infant formula, keeping it safe and fresh is just as important as choosing the right one. A few mindful steps can make all the difference in ensuring every bottle you prepare is both nourishing and worry-free.

Check refrigerator temperature - Make sure your fridge stays at 40°F (4°C) or lower. Stash bottles toward the back where the temperature is steady, instead of near the door or vents where it fluctuates.
Follow time limits - Don’t ignore the 24 hour fridge life recommendation—once mixed, use your formula as soon as you can.
Label bottles - Jot down the date and time on each bottle before refrigerating. This simple step makes it easier to keep track and ensures you don’t push past that 24-hour window.
Never reuse leftovers - If your baby has already had a sip, don’t save what’s left. Saliva can introduce bacteria quickly, so it’s always safer to prepare a fresh bottle.
Practice clean preparation -Wash your hands thoroughly and sterilize bottles, nipples, and caps before every mix. Boiling, steaming, or even the dishwasher can do the trick—just be sure items air dry completely before use.
Prepare only what’s needed - Mix just enough formula for one feeding at a time. Not only does this cut down on waste, but it also lowers the risk of contamination.
Heat bottles safely - Warm bottles gently in a bowl of warm water or with a bottle warmer—never in the microwave, since it can create hot spots. Always test the temperature on your wrist, and discard any reheated formula your baby has already started drinking.

Signs Formula Has Spoiled

It's important to carefully check baby's bottles of formula for any signs of spoilage before feeding. Look for:

Change in color - Formula that is still good should be consistent in color throughout the bottle. Yellow, brown, or gray discoloration could indicate spoiled formula.
Change in texture - Good formula is uniform in thickness and consistency. Clumps, curdling, separation, sliminess, or chunkiness are red flags for spoilage.
Unpleasant odors - Formula should have little to no odor when fresh. Foul, sour, or strange smells like curdled milk, rotten eggs, or chemicals point to spoilage.
Mold - Check the inner bottle walls and formula surface for fuzzy mold spots or film. This likely means bacteria has multiplied.
Gas bubbles - Bubbles on the formula surface or fizzing when shaken could indicate fermentation due to bacteria.
Past expiration date - Always check formula can or bottle labels and do not use any past expiration.

When in doubt, throw it out. Any signs of spoilage mean the formula is no longer good to give the baby. Bacteria and toxins multiply rapidly in expired and spoiled formula, and it's simply not worth the risk. Trust your eyes and nose - if the formula seems "off" in any way, do not feed it to your infant. Stay vigilant when storing and preparing bottles to detect problems before feeding.

What are the Risks of Spoiled Baby Formula?

Feeding a baby spoiled formula can be dangerous. Here are some of the potential risks.

Food poisoning
Nutritional deficiency
Digestive issues
Weakened immunity
Kidney problems
Poor growth and development

Be vigilant about proper formula handling and storage and you’ll have nothing to worry about. As always consult your pediatrician with any issues.

FAQs About Baby Formula

How do you store breast milk vs formula?

Breast milk and formula have different guidelines, including when it comes to storage. For comparison, here are CDC guidelines on breastmilk storage.

On the countertop: Up to 4 hours
In the fridge: Up to 4 days
In the freezer: 6-12 months

Breast milk should be stored in clean bottles or storage bags designed for breastmilk. Limit storage times and don't refreeze thawed milk.

Can you reheat a bottle of formula?

So, can you reheat formula? It’s best not to reheat formula once your baby has already started drinking from the bottle. Bacteria from your baby’s mouth can grow quickly in leftover milk. If you need to warm a freshly prepared formula bottle, use a bowl of warm water or a bottle warmer—never a microwave, since it can create dangerous hot spots. Always test the temperature on your wrist before feeding.

How long is formula good for after a baby drinks from the bottle?

Once your baby has had a sip, the countdown is short. Any formula left in the bottle should be used within one hour and then discarded, even if it’s been kept in the refrigerator. This prevents harmful bacteria from multiplying and keeps every feeding safe. To reduce waste, try mixing only what you know your baby will drink at one time.

How do you store formula when traveling?

Travelling can be stressful enough, you don’t need to worry about your formula too. Here’s how to safely travel with baby formula.

Take powder formulas for easier transport and storage.
Pre-measure powder formula into bottles before leaving.
Use insulated bottle bags, small coolers, and ice packs to keep bottles cool.
Discard any bottles that sit out for over 1 hour, or 2 hours if refrigerated.
Find tips on flying with breast milk and formula for smoother travel days.

Play It Safe & Shop Bubs

Once you’ve stocked up on clean baby formula for your little bub, safety and cleanliness are key next steps for building a feeding routine. From refrigeration to preparation, these simple guidelines for safe formula use will help keep your little one happy and healthy meal after meal. Starting from square one? Find advice on choosing the right baby formula and shop clean formula options today.