Unopened infant formula is good until the “Use By” date printed on its container, which is typically 12 to 18 months from the date of manufacture depending on the brand and format. After that date, the manufacturer no longer guarantees that the formula meets its labeled nutrient levels. The FDA requires every container of infant formula to carry this date, making it one of the few food products where expiration labeling is federally mandated rather than voluntary.
What the “Use By” Date Actually Guarantees
The “Use By” date on infant formula is not a rough suggestion the way “Best By” dates are on most grocery items. The FDA requires manufacturers to select this date based on testing that confirms two things: that every nutrient listed on the label is present in at least the declared amount, and that the formula remains safe and acceptable in quality. Until that date, a properly stored, sealed container should deliver the full nutritional profile your baby needs.
This matters more for formula than for almost any other food product. Infants who are exclusively formula-fed have no other source of nutrition. If key nutrients have degraded below labeled levels, a baby could consistently receive less than what their growing body requires without any visible sign of a problem.
What Breaks Down After Expiration
The nutrients most vulnerable to degradation over time are the fats, specifically the polyunsaturated fatty acids like DHA and ARA that are added during manufacturing to support brain and eye development. These fats are chemically unstable and prone to a process called oxidation, where exposure to heat, light, or simply enough time causes them to break down into byproducts that taste off and can be harmful.
Research published through the National Institutes of Health found that these oxidation byproducts include compounds like aldehydes that are potentially toxic. Infants are especially vulnerable because their detoxification systems are immature and their body weight is low, meaning even small amounts of these byproducts represent a proportionally larger exposure. Certain vitamins, particularly vitamin C and some B vitamins, also degrade over time, though fats tend to deteriorate fastest in powdered formulas.
How to Store Unopened Formula
Proper storage is what keeps formula viable through its full shelf life. The label will include specific storage instructions from the manufacturer, but the general rules are straightforward: keep unopened containers in a cool, dry place away from direct sunlight and temperature extremes. A kitchen pantry or cabinet works well. Avoid storing formula in a garage, car, or near a stove where temperatures can swing significantly.
Heat accelerates fat oxidation, so a container stored in a hot environment for weeks may lose quality faster than the “Use By” date suggests, even if the seal is intact. The expiration date assumes reasonable storage conditions.
When to Reject an Unopened Container
Even if the date looks fine, the physical condition of the container matters. Do not use formula from any container that is dented, bulging, leaking, or showing rust spots. A dent along a seam can compromise the seal and allow air or bacteria inside. A bulging lid can signal bacterial activity producing gas. Both MedlinePlus and the CDC flag these as safety concerns worth taking seriously.
Cronobacter, a rare but dangerous bacterium that can cause severe infections in newborns, is one specific risk associated with contaminated powdered formula. While contamination is uncommon, a compromised container raises the odds. If the packaging looks damaged in any way, it is safer to discard it and open a fresh container.
Unopened vs. Opened Shelf Life
There is a significant difference between how long formula lasts sealed versus after you break that seal. Once you open a container of powdered formula, most manufacturers recommend using it within one month. Write the date you opened it on the lid so you can track this easily. Keep the lid tightly closed and store the open container in a cool, dry spot, but not in the refrigerator, where moisture can get into the powder and promote clumping or bacterial growth.
Ready-to-feed and liquid concentrate formulas have even shorter windows once opened, typically 48 hours in the refrigerator. The key distinction is that an unopened container with months left before its “Use By” date has a dramatically shorter usable life the moment you open it.
Can You Use Formula Past Its “Use By” Date?
It is not recommended. Unlike many pantry staples where an expiration date reflects peak quality rather than safety, infant formula’s “Use By” date carries regulatory weight. After that date, nutrient levels may have dropped below what the label claims, and fat degradation byproducts may have accumulated. You would have no way to detect these changes by looking at or smelling the powder, since early-stage oxidation is not always obvious.
For an adult, eating something slightly past its prime is rarely consequential. For a newborn whose entire diet comes from a single source and whose organs are still developing, the margin for error is much smaller. If you find an unopened container past its date, replacing it is the safer choice.