How to Heat Up Formula in a Bottle

If you prepare your infant's formula just before using it, you don't have to worry about heating it. However, if you prepare it ahead of time and store it in the refrigerator, you'll need to heat it before giving it to your child. You can also store opened containers of ready-to-feed formula or concentrate formula in the refrigerator for up to 48 hours, but again, you'll have to heat it before feeding it to your infant. It only takes a few minutes to heat refrigerator-stored formula.

Mix the formula according to the packaging directions. Use warm water to prepare the bottle if you plan to feed it to your baby right away, so you don’t have to heat the bottle. If you are preparing it ahead of time, use cold or warm water and place the bottle in the refrigerator for later use. Usually the correct mixing ratio is one level scoop of powdered formula for every 2 ounces of water. If you're using liquid concentrate, follow the directions on the concentrate, but you typically mix equal parts of water and concentrate. Ready-to-feed formula doesn’t require mixing 2. If you mix formula, you should use it within one hour, or store it in the refrigerator within one hour. If you leave it outside the refrigerator for more than an hour, throw it away. You can store formula that you mix yourself in the refrigerator for up to 24 hours, notes the KidsHealth website. If you leave it in the refrigerator longer, you should discard it.

Sterilize your water before using it to prepare formula if your local or state health departments label your water as unsafe to drink. To sterilize, bring cold tap water to a rolling boil over medium heat, letting it boil for about a minute. Once the water cools to room temperature, mix it with your formula according to package directions.

Pour some hot water into a large ceramic mug or bowl to reheat a refrigerator-stored bottle of cold formula. Submerge the bottle of cold formula into the hot water -- and allow the formula to warm in the water for a few minutes. Alternatively, you can run the bottle under very warm or hot water for a few minutes.

Sprinkle a small amount of formula onto your wrist to test the temperature. If it's lukewarm, it's ready. If it is still too cold, place it back in the hot water or replace the water in the mug or bowl with fresh hot water. Test the temp again in a few minutes. If the formula is hot when you test it, allow it to cool on the counter for a bit. Retest and serve when ready.


You can also use bottle warmers that either sit on your countertop or plug into your car's lighter. Follow the instructions on the product’s packaging.


Never heat a bottle of formula or breast milk in the microwave, cautions, a website of the American Academy of Pediatrics. The microwave will heat the milk unevenly causing "hot spots" that can burn your child's mouth.

Never reheat a bottle of formula that your baby didn’t finish the first time around. Bacteria growth can occur from your baby’s saliva mixing with the milk. This can make your baby sick if she drinks it.

If you decide to heat water on the stove before submerging the bottle in it, you must remove the water from the heat source first, as you don’t want to damage the bottle.

Before using nipples and bottles for the first time, you should sterilize them in rolling boiling water for 5 minutes. You can also sterilize them with a store-bought countertop or microwaveable sterilizer, but boiling works just as well.