Infant formula is highly perishable and comes in three forms: powder, concentrated liquids or ready-to-use in milk-based, soy, lactose-free and hypoallergenic formulations. Prepared formula is good for 24 to 48 hours if stored in the refrigerator at 40 degrees Fahrenheit or below, depending on your chosen formulation. The World Health Organization recommends that powdered or concentrated formula is made fresh each time, whether for institutional or in-home use, as formula made up in batches creates a possible breeding ground for bacteria. Ready-to-use formula should be discarded after each feeding. All prepared formula should be discarded within one hour after feeding your baby.
The least-expensive type is powdered formula, which can be made and stored in the refrigerator 24 hours ahead of time. Make formula as directed on the package, usually one unpacked level scoop to 2 ounces of sterile water. Keep individual sterilized bottles tightly closed. A sterilized pitcher with closed lid may also be used. Cans or tubs of powdered formula last about one month after opening.
Concentrated Liquid Formula
Like powdered infant formula, concentrated liquid formula must be mixed with sterile or boiled-then-cooled water. Concentrated formula is prepared at a 1-to-1 ratio of formula to water. It can be stored in the refrigerator for up to 48 hours at 40 degrees or below. Once used, discard after one hour if baby doesn't finish the bottle.
Ready-to-use formula is expensive because the manufacturer has done all the prep work for you. It is premixed and premeasured. Just open the bottle, warm it (if you choose) and feed your baby. Never water it down, or it will be diluted or contaminated with microorganisms. Like concentrated liquid infant formula, you can store ready-to-use infant formula up to 48 hours in your refrigerator at 40 degrees or below.
Traveling and Other Considerations
If you need to travel with prepared formula, consider traveling with either powdered infant formula that you can make on the fly using sterile water or single-serving ready-to-use bottles. Do not freeze infant formula to use during travel. Freezing formula is not recommended at any time. If you're not traveling but have electrical issues at home due to a power outage or natural disaster, ready-to-use single-serve bottles are ideal because formula that warms to room temperature or sits in a warm refrigerator must be discarded after one hour.