The Baby Bottle Basics: How to Mix and Store Formula

Wondering about the correct formula-to-water ratio? How about whether it’s okay to reheat formula? Whether you’re looking for answers to questions about proper storage of baby formula or mixing tips and tricks, we’re here to help!

In this guide, we’re answering questions, providing important safety information, and giving step-by-step instructions on how to prepare your baby’s formula. Following these instructions will save you time and help you keep your formula-fed baby happy and healthy.

Skip to - Before you start: choosing a formula
Skip to - How to prepare Similac^® powder formula
Skip to - Similac ready-to-feed formula instructions
Skip to - How to warm a bottle
Skip to - Have questions? Don’t keep them bottled up!

Before you start: choosing a formula

Choosing the right formula will largely depend on your pediatrician’s guidance and your baby’s individual needs. Baby formulas are not “one-size-fits-all.” What’s best for one baby may not be best for yours! The right formula will be one that is easy for your baby to digest and supports their nutrition needs.

Check out our Formula Guide to learn more about the different Similac formula options. If you’re not sure which formula is best for your baby, ask your baby’s doctor. In addition, our Formula Finder can provide suggestions based on your baby’s needs!

Baby bottles: what kind should I use? 

You can use any bottle that your baby prefers or is recommended by your pediatrician. For more advice on bottles and nipples, take a look at our Bottle Guide.

How to prepare Similac^® powder formula

Follow these simple steps to protect your baby’s health and make sure they receive the nutrition they need. You can always refer to the specific preparation instructions that are printed on the side of your formula container.

Note: Before prepping your formula, remember to always check the date on your formula can. Never feed your baby expired formula or formula from a dented can.

1. CLEAN & SANITIZE. First, wash your hands well before preparing bottles or feeding your baby. Next, clean and sanitize the workspace where you will be preparing your formula.

2. ADD WATER TO BOTTLE. Measure and pour the appropriate amount of water into a clean baby bottle.

3. ADD POWDER FORMULA SCOOP(S) TO BOTTLE. Add unpacked, level scoop(s) of powder formula to the bottle as directed (1 scoop of formula per 2 fl oz of water). Return dry scoop to can. Scoop sizes can vary, so it’s important to use the scoop that comes with your product.

4. CAP & MIX BOTTLE. Put the cap on the bottle and shake.

5. READY TO FEED! Feed or store immediately in refrigerator.

6. CLEAN YOUR BOTTLE. Baby bottles, nipples, and rings should be cleaned after every feeding. Make sure to take bottles fully apart and thoroughly clean each part.
   

Do I need to use boiled water to make baby formula?

Ask your baby’s doctor if you need to use cooled boiled water for mixing and if you need to boil (sterilize) bottles, nipples, and rings before use.

Extra steps, such as sanitizing feeding equipment like bottles and nipples, may be necessary, especially if your baby is younger than 2 months old, was born prematurely, or has a weakened immune system. For more information on cleaning and sterilizing bottles before use, refer to the CDC website.

Reminder: Powdered infant formula is not sterile and should not be fed to premature infants or infants with immune problems unless directed and supervised by your doctor.

Store unopened and opened formula containers in a cool, dry place. They should not be kept in places with extreme temperatures. Do not store your powder formula containers in the fridge.

Once opened, tightly close the lid of your container after each use, and make sure to use all of the product or discard the unused portion within 1 month of opening. Consider writing the date you opened your formula on the can to help you keep track!

Storing prepared powder formula

Once mixed, feed immediately or refrigerate in a securely closed container. Do not freeze mixed formula—this can cause the protein and fat to separate. Once prepared, formula should be used within 24 hours.

Formula-to-water ratios

For Similac formula, use 1 level scoop of powder (not packed down) per 2 fl oz of water. Your baby's health depends on carefully following these directions.

Remember: Scoop sizes can vary, so it’s important to use the scoop that comes with your product.

Here’s an example of what your label may instruct you to do: 

Supplementing breast milk with formula may be an option that supports your feeding goals. While you can alternate between breast milk and formula, it’s also okay to mix breast milk with prepared formula.

See our article for more information on introducing formula to your breastfeeding baby. 

What temperature should baby formula be?

Baby formula can be served cold, room temperature, or warmed.

If you do choose to warm your formula, it’s important to do it safely. See how to properly warm a bottle below.

How much should I feed my baby?

Your baby will need different amounts of formula at different stages in their development. Babies also give certain cues to tell you when they’re full! To learn more about how much formula your baby needs, see our article on formula feeding.

Similac ready-to-feed formula instructions

Ready-to-feed formula is what it sounds like—ready to go when you need it! It’s a great option to make nighttime feeding or feeding while traveling more convenient.

There's no mixing required and only minimal prep work. Simply wash your hands, shake the ready-to-feed bottle before opening, and pour the formula into a clean baby bottle. Or, if you’re using a 2-fl-oz or 8-fl-oz ready-to-feed bottle, just twist on the nipple and ring. It’s that easy!

Note: If your baby doesn't finish a bottle of formula within 1 hour, throw it away.

How to store unopened ready-to-feed bottles

Store unopened ready-to-feed formula at room temperature; avoid extreme temperatures and protect from light. Store in original packaging until ready to use.

Storing ready-to-feed formula once opened

Storage of opened ready-to-feed formula will depend on which formula you are using.

• 32-fl-oz bottles: Immediately store the open 32-fl-oz bottle in the refrigerator. Use the remainder of the formula within 72 hours of opening. If you pour the 32-fl-oz bottle into individual baby bottles, refrigerate them, and use within 48 hours.

• Alimentum® 32-fl-oz and 8-fl-oz: Store capped, opened container immediately in the refrigerator and feed within 48 hours. If using Alimentum 8-fl-oz ready-to-feed can, cover opened container and store immediately in the refrigerator. Feed within 48 hours.

• 2-fl-oz and 8-fl-oz nipple-ready bottles: Store immediately in the refrigerator and feed within 48 hours.

Do not reuse ready-to-feed bottles. Protect opened bottles from light.

How to warm a bottle

Baby formula doesn’t need to be warmed, but if you prefer to warm it, do not microwave it. Microwaving baby formula can cause “hot spots” that can burn your baby. Instead, try one of the following methods.

Appropriate ways to warm formula

Water bath. Set the filled and capped bottle in a bowl of warm (not boiling) water. Make sure the top or neck of the bottle does not touch the water. Before feeding, swirl or shake the bottle to distribute warmed formula evenly, then sprinkle a few drops of formula on the inside of your wrist to make sure it’s not too hot.

Warm running water. Hold the capped bottle under warm running tap water. Make sure the top or neck of the bottle does not touch the water. Before feeding, swirl or shake the bottle to distribute warmed formula evenly, then sprinkle a few drops of formula on the inside of your wrist to make sure it’s not too hot.

Can you reheat formula?

Unfortunately, no. Once formula has been prepared and warmed, it’s best to serve it to your baby right away. Feeding reheated formula can negatively impact your little one’s health, as reheating can increase the potential for bacteria to breed and increase the risk of foodborne illness. Once feeding begins, use within 1 hour.

Have questions? Don’t keep them bottled up!

Find answers to some of your frequently asked questions below.

How much should I be feeding?

Your baby will need different amounts of formula at different stages in their development. Babies also give certain cues to tell you when they’re full! To learn more about how much formula your baby needs, see our article on formula feeding.

After opening a container of ready-to-feed formula, how long can it sit out?

If not being fed to your baby, formula should be immediately stored in the refrigerator until your baby’s next feeding.

Can I store Similac powder formula in a different container than the original can?

We recommend keeping Similac powder formulas in their original containers. Our packaging containers are specifically designed for infant formula. They are made up of several layers that include barriers to oxygen and light, which can break down light-sensitive vitamins in our formula. A clear container or jar would not have these special layers.

Please note that each Similac container may have a different batch number and expiration date; this is another reason to keep powder in the original container.

Can I make a large batch of powder formula, or should I make individual bottles?

Yes, you can save yourself time by making multiple bottles of formula at once! If you are preparing a larger amount, just make sure to only prepare what your baby would drink in a 24-hour period. Then pour the prepared formula into individual feeding bottles, cap and store them immediately in the refrigerator, and use within 24 hours.

How can I prevent my formula from getting clumpy?

Clumps can form in your formula if the water and powder don’t get thoroughly mixed. It is important to measure the water carefully and add it to the mixing container or bottle first, then add the powder.

My baby doesn’t seem to like the formula I’m giving them.

If your baby isn't responding well to the formula you’re using, consult your pediatrician. It’s possible that it’s not the right formula for them. Try our Formula Finder and our Tummy Trouble Tool for customized suggestions on how to help your little one feel better. It’s also possible that your baby isn’t liking the bottle or nipple you’re using. Take a look at our Similac bottles and nipples for new options.

How long does powder formula last once prepared?

Once mixed or refrigerated, baby formula must be used within 24 hours.

How far in advance can you make baby formula?

You can make baby formula up to 24 hours in advance. See the above instructions on how to prepare a batch of formula for more information.

Can you make baby formula with distilled water?

Yes, you can use distilled water to make formula. Tap water is normally safe, but if the water becomes unsafe in an emergency, such as a flood or a hurricane, you can use either distilled or purified water. Ask your baby’s pediatrician for the safest option for your baby.

Can I make my own homemade baby formula?

We do not recommend using a homemade baby formula. Using homemade baby formula can lead to serious health problems for your baby. Your baby’s nutrition needs are very specific, especially in their first year of life, and homemade formulas may contain too little or too much of certain components, such as vitamins and minerals (like iron). They may also have an increased risk of contamination, which could make your baby sick.

How can I save money on Similac formula and get other feeding support?

To save money on formula and more, sign up to join MySimilac^® Rewards.

Have questions we didn’t cover? Consider getting live support from our Feeding Expert team by calling 800-986-8800 (8:30 AM – 7 PM ET) or talk to your doctor for more information.