Can You Refreeze Breast Milk? What the CDC Says

It happens to everyone with a freezer stash: you thaw a bag, your baby takes less than expected, and now you’re staring at milk you worked hard to pump. Putting it back in the freezer feels like the obvious fix.

The CDC’s answer is no, with one narrow exception. Here’s exactly what the rule says, what counts as “thawed,” and what to do with milk you can’t use. This is for healthy, full-term babies.

The rule: never refreeze thawed milk

The CDC’s breast milk storage guidance says: never refreeze breast milk after it has thawed. Its printable chart repeats it in two places, in the thawed-milk row and again under the thawing instructions. The NHS says the same: do not refreeze milk that has been defrosted.

That applies whether the milk was thawed in the fridge, in warm water or under running water, and whether or not your baby touched it. Once it has thawed, the CDC’s options are to feed it, refrigerate it for a limited time or throw it away.

Why the rule exists

The CDC states the rule without explaining it on the pages we read. La Leche League is more direct about what’s known: there is little research on the safety of refreezing human milk, but it may cause further breakdown of nutrients and increase the risk of bacterial growth, so the accepted practice is not to do it.

You may see people point out that USDA’s general food-safety guidance allows refreezing some foods, such as raw meat, that were thawed in the refrigerator. That guidance is about meat, poultry and other foods in general and says the food may lose quality. It isn’t breast milk guidance, and the CDC’s rule for breast milk is stricter. Follow the CDC’s rule for your baby’s milk.

The one exception: milk that still has ice crystals

The CDC’s FAQ on power outages says that frozen breast milk that has started to thaw but still contains ice crystals can be refrozen. This is the only refreezing allowance on the pages we read. It’s written for situations like a freezer failing and then coming back on.

The CDC doesn’t define how much ice is enough, so be cautious:

• Still hard or slushy with ice crystals throughout: may be refrozen.
• Completely liquid: treat it as thawed. Don’t refreeze.
• Not sure: treat it as thawed and use it or throw it away. This is our cautious reading, not CDC wording.

What to do with milk that has thawed

Situation	What to do
Thawed in the fridge, not yet warmed	Use within 24 hours, counted from when it was completely thawed (CDC)
Completely thawed but still cold, for example after a power cut	Put it in the fridge and use it within the next day, or throw it away (CDC)
Thawed and now at room temperature or warmed	Use within 2 hours (CDC); the printable chart says 1 to 2 hours for thawed milk at room temperature
Leftover after a feed	Use within 2 hours after your baby finishes, then throw it away (CDC); the NHS says 1 hour and ABM Protocol #8 says 1 to 2 hours

Notice that “put it back in the fridge” is allowed, within 24 hours, for milk that was thawed in the fridge. “Put it back in the freezer” is not. Our guides on how to thaw frozen breast milk and how long warmed breast milk is good for go through the timings.

The AAP’s page says thawed milk is best used within 24 hours but may be used within 48 to 72 hours. That’s longer than the CDC’s 24 hours, so use the shorter limit if you want the most cautious path.

What you can freeze

The refreezing rule is about milk that has already been frozen. Milk that has never been frozen can go into the freezer:

• Fresh milk can be frozen (up to 12 months, with 6 months best, per CDC).
• Refrigerated milk can be frozen too. The CDC says if you think you won’t use breast milk within a few days, freeze it as quickly as possible. After 4 days in the fridge it should be used or thrown away.
• Freshly pumped milk shouldn’t be mixed into milk that’s already cold or frozen, because the CDC says it can rewarm the older milk. Chill it first and freeze it separately.

Our guide on how long breast milk lasts in the freezer covers freezer times and how to freeze milk well.

How to avoid wasting milk

Most waste comes from thawing more than your baby takes. These steps follow the CDC’s guidance:

1. Freeze small portions. The CDC suggests 2 to 4 ounces (60 to 120 ml), or the amount offered at one feeding. La Leche League gives a range of 1 to 4 ounces (30 to 120 ml).
2. Thaw one portion at a time. The CDC says to consider storing, thawing and warming milk in smaller amounts, and to thaw the oldest milk first.
3. Warm only what you need. If your baby wants more, warm a second portion rather than a large bottle.
4. Try it cold. The CDC says breast milk doesn’t need to be warmed. See can babies drink cold breast milk.
5. Use a storage calculator to check use-by times: our breast milk storage calculator can help.

If you’re also giving formula, see mixing breast milk and formula.

Where the sources agree and where they don’t

The CDC, NHS and La Leche League all say not to refreeze thawed milk, and none of the pages we read offers a method for making it safe to do so. ABM Protocol #8, which the CDC’s chart is adapted from, is less definite: it says there is little information on refreezing thawed milk and that no recommendation can be made. The AAP page we read doesn’t address refreezing. The exceptions and timings differ slightly: the CDC allows refreezing only while ice crystals remain, and the AAP and CDC give different windows for thawed milk in the fridge. When two sources differ, the shorter window is the safer one.

For the full set of storage times, see our breast milk storage hub.

When to call a doctor or lactation consultant

Call your baby’s doctor if your baby seems unwell after drinking stored milk, for example with fever, vomiting or diarrhea, or if your baby was born early or is in the NICU and you need storage instructions for your situation.

If you keep ending up with leftover milk because your baby takes small amounts, or you’re worried about whether you’re pumping enough, a lactation consultant (IBCLC) can help. See our breastfeeding support page for ways to reach one.