How long does Prepared baby formula last in the fridge once opened?
Turning the range into a date
Prepared baby formula keeps 1 day in the fridge once opened. Two clocks run on this item: one from the day it went into storage and one from the day the seal broke. Both are listed below, 1 row in all.
- Once opened · in the pantry1 hour, and no date will help: it is shorter than a day
- Once opened · in the fridgeUse by1 day after the day you opened it
The edge of its own category
This item is the shortest-lived entry in the Baby Food list: 1 day outside the freezer, against 2 days for Liquid concentrate or ready-to-feed formula, the item immediately above it. All 5 of the others keep longer. It stands 6 of 6 on its shelf, one step below Liquid concentrate or ready-to-feed formula at 2 days. Prepared and prepare are the same food in the source list.
Every storage figure the USDA publishes for this item
The USDA gives this item a pantry and a refrigerator figure and no freezer figure at all, the pattern behind 79 of the 466 foods in the data.
- Once opened · in the pantry1 hour
- Once opened · in the fridge1 day
Why this page prints no multiplier against the room-temperature figure
The USDA's figure in the pantry once opened is 1 hour, and 1 hour is a limit on standing at room temperature rather than a window for storing it. No multiplier is printed on this page at all. A ratio whose denominator is a safety limit turns a danger-zone rule into a benefit, and there is no second window here to divide by instead.
What the USDA adds in words
The USDA attaches 1 handling note to this item, reproduced below word for word. It is about safety rather than quality, which is the distinction this data is easiest to get wrong. These are the source's own sentences, not ours, and they are the part of the FoodKeeper record that a table of durations cannot carry.
In the pantry. Should be discarded after use-by date.
Can you freeze prepared baby formula?
FoodKeeper gives prepared baby formula no freezer time, and this site does not fill that gap: go by the window above, 1 day in the fridge once opened. The FDA does not recommend freezing infant formula: its components may separate. Keep the fridge at 40 °F or below and the freezer at 0 °F.
How to tell if prepared baby formula has gone bad
Go by the date first: prepared baby formula keeps 1 day in the fridge once opened. A sour or off smell, mold, slime or an odd color mean it goes out. The bacteria that make people sick change none of these, so past its window it goes out even if it seems fine. Never taste to test.
Sources: USDA FSIS: the danger zone USDA FSIS: freezing and food safety USDA FSIS: molds on food FDA: infant formula safety do's and don'ts FDA: are you storing food safely FoodSafety.gov: the FoodKeeper app.
Is it still safe to eat, or just past its best?
The answer at the top of this page reads 1 day in the fridge once opened. What decides that is the food: the source files Formula, prepared under Baby Food, a heading it keeps for perishable food. Past it, it is not safe to eat: throw it out without tasting, because bacteria build up while food still looks and smells fine.
It is past the date. Now what?
Say the calculator above puts Formula, prepared past its 1 day in the fridge once opened window, or the container sat out on the counter overnight. Throw the container out without tasting it, and count any hours it already spent out of the refrigerator as part of that window rather than on top of it.
The USDA's limit for perishable food standing at room temperature is 2 hours, or 1 hour when the kitchen is above 90 °F, and that clock runs whatever the storage figure says. The USDA also caps this at 1 hour standing at room temperature. That is the clock running while food stands in a warm kitchen, not a shelf life. The whole rule, including the cases the source does not cover, is set out under what to do when the date has passed.
Two places, and one of them is the wrong one
The USDA rates two places for Formula, prepared in one state and they disagree: 1 day in the fridge once opened against 1 hour in the pantry once opened. This page answers with the refrigerator, the longer of the two. Both figures are the USDA's own, so this is a choice of where to put the food rather than a disagreement about how long it keeps.
Items that behave the same way
All 3 of the nearest items keep at least as long as this item, 3 days to 1 month against its 1 day: it is the bottom of its own cluster.
Where these numbers come from
Every storage time on this page is the USDA’s own published figure from the FoodKeeper data, one of the 9 it keeps per food, reproduced unchanged and never an estimate of ours. Where the USDA lists several kinds under one name, each kind keeps its own windows, and the page names the kind its answer is for. The dates and multipliers are ours, computed from those ranges.
Source: USDA FoodKeeper, retrieved 1 September 2026. Found a figure that does not match the source? Tell us on the contact page. How the site is built is on the method page.
Also searched as: baby formula, infant formula
USDA index terms: Formula, prepare, prepared
KeepsUntil is an independent reference built on public USDA data. It is not affiliated with, endorsed by, or connected to the U.S. Department of Agriculture or the Food and Drug Administration. Whether a given window is a safety limit or a quality window is stated on the page that prints it.