My wife pumps and puts the milk in the fridge if it's not time for a feeding. We have to supplement with formula because the baby drinks about 4 more ounces a day than she makes. Feeding from the breast never worked out.

Anyway, the problem is, sometimes, we get the breast milk out and heat it up (running hot water over it or just holding it in warm hands) and the milk looks curdled. We just throw it out and grab a different bottle of breast milk whenever that happens out fear that it has gone bad.

Why does that happen? Is the milk still safe? It's never in the fridge for more than a day or so and we make sure to rotate them and even have some contraption where the new milk goes in one side and the oldest milk comes from the other side.

  • 1
    If it doesn't seem rancid and you've followed proper storage guidelines (which you have, breast milk can last at room temperature up to 10 hours and in the fridge up to 3-5 days), then as long as it doesn't seem sour it's fine. The link there has information on causes of breakdown in breast milk.
    – justkt
    Jul 7, 2012 at 12:51
  • Lots of different "guidelines" that range between 2 days in the fridge to 10 days. That's a big difference! But I like the smell test . . . I was never one to toss food just because it was past the expired date . . . it's more about how it looks and smells right at the point you want to eat it.
    – tooshel
    Jul 9, 2012 at 15:14
  • My milk sometimes separates in fridge which is cold enough but smells ok and my baby takes it's happily. I also give a feed of formula as night for last feed and it works for us! Keep doing what your doing if it works and don't let anyone tell you otherwise. I have friends and family who tell me at 9 weeks old I should just givd up expressing and just use formula as its hassle to express!! I don't think it is as she is getting my milk! I wanted to breast feed but she wouldn't stay latched on long enough to feed properly! Ra
    – user13768
    Feb 23, 2015 at 16:10
  • Smell test. Sometimes it looks unholy but if you swirl (not shake) the bottle and smell you will know if it is indeed bad.
    – Kai Qing
    Feb 23, 2015 at 21:19

3 Answers 3


Breast milk will separate. Just lightly swirl it back together.

As long as you are following safe Breast milk storage guidelines the milk should be fine.

And please stop throwing it away, your wife worked hard to make that!

  • My wife wanted to toss the milk too! It was scary looking. But the "gentle swirl" to mix it back together was good advice from one of the links mentioned so far.
    – tooshel
    Jul 9, 2012 at 15:09
  • Sometimes it looked green to me. Diet, fat content, etc all play a role in the appearance. But if it doesn't smell like a rotting corpse, you are most likely ok
    – Kai Qing
    Feb 23, 2015 at 21:20

Milk bought in stores undergoes a process called homogenisation which ensures that globules of different sizes, which naturally exist in milk, are split into smaller pieces, which in turn allows the fluid to not separate when left on its own.

Breast milk is not homogenised, so larger fats will separate from smaller fats, all fats will separate from proteins and proteins will separate from water. In time, a gradient of heavier-larger molecules on the bottom and smaller-lighter molecules on the top will appear. This is completely normal. In fact, it would be very strange if it didn't happen.

You can just swirl the bottle a few times and the milk will be good as new:)

There are rules to how long can a milk be stored where:

  • In the fridge (~4 degrees Celsius) - 2 to 5 days (varies depending on the source, 2 days will be safe for sure); it also depends on temperature, the lower it is, the longer the milk will remain fresh. Also, you shouldn't keep the milk on the fridge door, since it's the hottest there.
  • It can lay up to 12 hours in room temperature.
  • It can be stored in the freezer for up to 3 months.

On the keeping up with production front, it was suggested to me that I pump about 20 minutes BEFORE at least one regular feeding (like at bedtime for example) after the first month or so. It increases production to have so much demand all at once. Just an idea to try.

  • 1
    The other option is right after a feeding, when the baby has already triggered the let down. You don't get much at once at first. There's also power pumping (pumping every 10 minutes over a long course of time).
    – justkt
    Jul 8, 2012 at 13:04
  • Beside not having ENOUGH milk I think another reason for the formula at night is that you can mix it right there in bed and don't have to get up and warm the milk. And the less time the baby cries for milk the less likely she'll stay up. And I kinda like mixing it up and having her drink formula too . . . maybe this early variety will mean she'll eat something other than chicken nuggets shaped like dinosaurs.
    – tooshel
    Jul 9, 2012 at 15:13

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