My wife is currently pumping just enough milk to keep up with "demand". Since she'll be going to back to work and won't be able to pump as often as she does now, her milk supply will likely run out before the baby stops needing it. We're considering freezing some of the breast milk now and supplementing whatever is frozen by formula, so that we can feed the combination of formula/breast milk for a much longer period of time.

Is this a good idea? Or is it better for the baby's immune system to feed all the breast milk now and later on be 100% on formula?

  • How old is your baby?
    – J.J.
    Commented May 24, 2011 at 1:42
  • Baby is two weeks old. Thanks for all the replies!
    – Igorek
    Commented May 25, 2011 at 0:17

6 Answers 6


I don't know about better or not, but I can say from experience that after several months of nothing but the real thing, my son would NEVER drink a bottle of pure formula, adding just an ounce of breast milk to 12 ounces of formula and he would devour it. So if you're going to HAVE to switch to formula, keeping a little bit around to make it palatable sure seems like a good idea. That said, freezing only lasts so long, and once you thaw it you only have a few days to use it... so don't freeze in huge bottles.

  • 3
    Tip: use ice cube trays in order to be able to thaw just the right amount.
    – Tim H
    Commented May 25, 2011 at 8:40

Here is my advice based on my personal experience pumping breastmilk for twin boys for a full year. Of the 12 months I supplemented with formula for about 5 of them.

Your little one is only 2 weeks old so you have a bit of time before you have to worry about it. Your wifes supply will change quite a bit over the next few months. There is a good chance that she will make more than enough milk and still have extra to freeze.

Your wife should continue pumping as long as she can.
I found that when I went back to work it was actually easier since I was on a very strict and regular schedule.

Don't be afraid to mix formula. (Unless your wife is going back to work soon, I would hold off until your little one is at least a month old.)
What I did when going back to work was to add an ounce of formula to each bottle through out the day and then at the end of the day freeze whatever milk was left in the fridge. It helped me to set up a nice freezer supply gradually over time.

Spend the extra money and buy the small 8oz bottles of formula
Because your little one is getting primarily breastmilk they won't use very much formula. Powdered formula expires about a month after it has been opened. I spent extra money and got a case of the 8oz travel bottles of Similac formula. It ended up saving me a ton of money in the long run. One thing to be careful of is to try the brand of formula you want to use first to make sure the the little one won't react to it.

Buy extra storage bottles for the fridge.
I used a Medela pump and bought a total of 9 storage bottles for it. It allowed me to use them to store and transport the milk without having to wash bottles constantly. I only used the milk storage bags for freezing.


Be aware that -

  1. you can't store frozen breast milk for ages. Check with a nurse in your community, as the recommendation varies by country. In Austria, I think they say 3 months.
  2. thawed breast milk must be consumed quickly. Ask the nurse; in Austria they say 24 hours. As @cabbey says, it's best to freeze one serving apiece.
  3. milk production varies over time and is directly linked to how much is consumed/pumped; keep breastfeeding and perhaps the production will go up. Not certain though; every person is different.
  4. "before the baby stops needing it" is very subjective. Some moms stop breastfeeding after two weeks, some after 9 months or more.
  5. my understanding is that because breast milk helps train the immune system, I believe it would be best to breastfeed as much as possible early to get the immune system ready, and then you don't need to consider that anymore when you switch to formula.

I have no personal experience with mixing breast milk and formula, so I can't comment on that.

Update: since you now say the child is only 2 weeks old, it's worth adding that breastfeeding as exclusively as possible is the best basis for a healthy immune system.


Breastmilk can be stored in a deep freezer (not the freezer on your fridge) for up to 6 months (at 0F). It can be stored in a standard fridge/freezer freezer compartment for 3 months, and if it's an 'apartment sized' aka mini fridge with a freezer compartment in it, just 2 weeks.

If you're in doubt as to storage, call your local La Leche League.

  • You just need to make sure to rotate through it so that it gets used before it expires. Commented May 25, 2011 at 16:05
  • Did you mix up the degrees? Deep freezer should be -18 C or colder, not 0 C. Commented May 25, 2011 at 18:37
  • It's possible, I was tired when I wrote it, and since it's a US site, it's most likely supposed to be F. I'll fix that.
    – Darwy
    Commented May 25, 2011 at 22:33

Just to offer a different experience, our daughter is just fine on formula when shes not drinking breast milk (probably a 50/50 mix). Similac, Enfamil, Costco brand...whatever. Definitely get a nice big carton of the stuff and try it out with no breast milk...your baby may not care one way or the other. As for the health benefits...do NOT worry about skipping some of the time. My understanding is that if you can keep at least a modest amount of breast milk in the mix for the fist nine to twelve months you get all those great benefits to IQ and the immune system. Modern formula has a really nice mix of nutrients and fatty acids, so its not like you're switching to crap for your baby. Good luck!


I understand that the first 3 days are the most important, so much so it is vital you do it then. From there on, I believe it is just very good for the baby. My wife settled at 12 months for breastfeeding, onto cows' milk then, bypassing formula. The important transfer is done by 3 days, so I believe everything after that is the icing on the cake.

However, it is hard to comment further as I don't know how old the baby is.

The NHS suggests that Breastfeeding is the healthiest way to feed your baby.

Exclusive breastfeeding (giving your baby breast milk only) is recommended for around the first six months (26 weeks) of your baby's life. After that, giving your baby breast milk alongside other food will help them continue to grow and develop Any amount of breastfeeding has a positive effect. The longer you breastfeed, the longer the protection lasts and the greater the benefits.

Infant formula doesn't give your baby the same ingredients or provide the same protection. Breast milk adapts to meet your baby's changing needs.

Breastfeeding NHS

I was at a christening the other day where a lady was breastfeeding her 6 year old son. I was surprisingly shocked.

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