Can I pour pumped milk from different sessions together? Fridge is full of tiny bottles

My fridge door looks unhinged. I'm back at work pumping twice a day and I keep ending up with little bottles of 40ml, 60ml, one sad 25ml, all from different sessions and different days, and I never know what I'm allowed to do with them.

Can I just pour this morning's pump in with yesterday afternoon's to make one proper bottle? What about the freezer, I've got a bag that's only half full, can I keep adding to it over a couple of days or does each bag have to be one session? And the bit that really scrambles my brain: if I pump a warm fresh lot, can it go straight in with milk that's already cold, or on top of a frozen bag?

I feel like there's a rule for all of this and I'm one wrong pour away from wasting milk I cried while producing.

You can absolutely combine, this is what got me through a year of pumping without a fridge full of thimbles. Same day sessions I combined without much drama. The one thing I was careful about: chill the fresh warm milk in the fridge first, THEN add it to the already cold stuff, rather than pouring warm straight onto cold. Adding warm milk to cold or frozen milk partly warms the older milk back up and that's the bit you don't want.

For the freezer bag, I used to cool a fresh lot in the fridge and then add it to a chilled bag to fill it up, freezing flat helped it stack. Label every single one with the date you pumped it, oldest to the front, use oldest first. Sounds obsessive, saves so much waste.

I'll be the cautionary tale. With my first I genuinely just poured every fresh warm pump straight onto whatever was already in the fridge bottle, warm onto cold, no thought at all, and topped up frozen bags the same way. Nobody got ill and she's a strapping five year old now, BUT I later read you're meant to cool it separately first and I've done it properly since. So learn from me rather than from luck.

The numbers I keep in my head: fridge a few days, freezer months, and use the oldest first. But honestly I stopped trusting my memory on the exact hours and just keep the storage guide bookmarked on my phone, because the times are different for fridge vs freezer vs sitting out on the counter and I always mixed them up.

Becky, good news, almost everything you want to do is fine, you just want the order of operations right. Yes you can combine freshly expressed milk from different sessions, and yes you can keep topping up a freezer bag over a day or two, with one condition that Jess and Gemma have already landed on: cool the fresh warm milk down in the fridge first, then add it to milk that is already chilled or frozen. Adding body temperature milk straight onto cold or frozen milk part thaws and rewarms the older milk, and that is the thing worth avoiding.

The rough numbers, and they are ranges rather than hard lines: freshly expressed milk keeps at room temperature (around 16 to 25C) for up to about 4 hours, in the fridge (about 4C or colder, at the back not the door) for up to around 4 days, and in the freezer for several months, commonly quoted as up to about 6 months for best quality. When you combine two lots, treat the mixed bottle by the age of the OLDER milk in it, not the fresh addition, that is the safe way to date it. Label everything with the date pumped, front to back oldest first. One that catches people out: once baby has actually drunk from a bottle, use up or discard the leftover fairly soon rather than saving it back, because feeding introduces a bit of saliva. The breast milk storage guidelines lay all the times and temperatures out in one place so you're not doing this from memory at 4pm, and if you're building a proper stash the exclusive pumping guide has the wider logistics.

One caveat to name: these are the general guidelines for a healthy term baby. If your baby was premature, is in hospital, or has a health condition, the storage times are stricter and you should follow the specific advice you've been given rather than the general ones. For everyone else, breathe, your fridge door is fixable.

This is exactly what I needed, thank you. Spent ten minutes tonight with a marker labelling everything and rearranging oldest to the front, and I've got the storage guide saved now so I stop second guessing the hours. Cool first then combine, date by the older lot, use oldest first. The thimble era is over.