Bottle and formula feeding questions and answers

The Pediatric Insider

© 2015 Roy Benaroch, MD


What’s the best way to warm up the bottle?

Cool formula can be warmed up safely by dunking the bottle in warm water. This method isn’t quick, but it works and it’s safe. There are also “bottle warmers” you can buy that surround the bottle with gentle warmth from all sides—though I am not sure they work any quicker than using warm water in the sink.

Bottle and formula manufacturers caution against using a microwave to heat a bottle. There is a possibility of creating “hot spots” either in the formula or on the nipple, with small areas becoming hot enough to burn.


Is it necessary to warm up a baby’s bottle?

No, it’s not necessary—but it’s traditional, and some babies get used to warm formula and don’t like it chilled. As babies get closer to weaning off the bottle at 12 months, many families back off the warming for convenience, and those babies do fine. There is no harm in trying cool or lukewarm formula to see if your baby likes it.


Should I use tap or bottled or boiled water to mix the bottles?

Ordinary city municipal tap water is fine. Tap water is very highly regulated, and is monitored far more closely than bottled water for purity. There is no reason to waste your money on bottled water or special nursery water. It is also unnecessary to boil tap water—it’s very clean right out of the tap. Heart surgeons wash their hands in that stuff, you know. And babies’ mouths (and mom’s breasts) are loaded with germs. Sterility is not necessary for feeding humans.

If your water supply comes from a well or cistern, check with your local water authorities for guidance on using that water for formula.


Do I need to boil or sterilize bottles and nipples?

No, running them through an ordinary dishwashing cycle or handwashing them is sufficient. Clean is good, sterile isn’t necessary.


How do I mix formula?

Always follow the instructions on the package, using the scoop that came with the product. Typically you’ll first measure the correct amount of water, then add the leveled scoops of powder. The exact proportions will be on the packaging. Mixed formula should be kept refrigerated and used within 24 hours. Once the package of powder has been opened, keep it in a cool dry place and discard any unused powder in one month.


What should I do with leftover formula if by baby doesn’t finish the bottle?

Throw it away. Once formula has been re-heated OR once a baby has taken any from the bottle, the formula should be considered contaminated and used within one hour, or discarded. Do not re-refrigerate warmed or partially-consumed formula.


Is there a kind of nipple or bottle system that’s best?

I don’t think so. There are many varieties, and some are marketed quite heavily with promises to reduce colic, or promises that they’re more like breast feeding. All of that is advertising hype. I suggest you purchase simple, cost-effective bottles and nipples.

Once choice you’ll have to make is to use traditional bottles versus the kind with the drop-in, disposable bags. While neither has any advantage for your baby, the drop-ins may save some trouble with fewer bottles to wash—in return for more plastic bags to throw away. Either style works well for most families.


Are generic or store-brand formulas any good?

They’re as good as name brand, commercial formulas. With name brands, you’re not getting a better or more-nutritious product—you’re just paying for fancier packaging and marketing hype.


Maybe I should just make my own formula. I found a recipe on the internet!

No, no, no, no. Do not make your own formula. It is not safe, it is not nutritious, and it is dangerous. Homemade cookies? Good. Homemade formula? Bad.


What about BPA and chemicals in plastic bottles?

In 2008 Congress banned BPA and several related compounds from baby products, based on sketchy and indirect evidence of potential harm. Still, it seemed prudent to avoid the chemical, as there were still unanswered questions about long term exposures. Since then, there’s now new concerns being raised about chemicals that have replaced BPA.

I say: there’s always something to worry about. And when things are really safe (ahem, vaccines), the modern media feeds into our own worries, especially about purity and food and children. I don’t think there’s any reliable evidence that parents need to worry about plastics used in baby bottles or spoons or anything else. But if you’re concerned, use glass bottles.



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9 Comments on “Bottle and formula feeding questions and answers”

  1. Gem Says:

    Thanks for the info on bottle and formula feeding. I don’t feel like there’s enough good info out there for mothers who can’t or don’t want to breastfeed.

    I just read a UK book called _Guilt-free Bottle Feeding_. In general it was a great book but I found the suggested techniques of bottle feeding to be very different than what I’ve heard in the US. Among other things, it says to boil the water and add the formula at 70C and then let it cool down to room temperature to kill any potential bacteria in the formula. I double checked and that appears to be what the UK NHS also says. Is this just a matter of how much risk each country is comfortable with? Is our formula in the US less likely to have bacteria contamination? Or is it something else entirely that is guiding this recommendation? I had to formula feed my first son and I can’t imagine going through that process every time he needed a bottle.


  2. Laurie Says:

    Thanks for this! Very helpful info.


  3. Dr. Roy Says:

    Gem, that sounds like what I would call A Big Hassle. I honestly don’t know why UK NHS has such specific instructions. It sounds kind of, well, silly.


  4. Rachel Says:

    I never understood the “don’t microwave bottles because there could be hot spots.” Wouldn’t shaking the bottle well before feeding eliminate the hot spots?


  5. Megan Says:

    This is so helpful. I never received much information since I had planned to breastfeed but my baby couldn’t due to tongue tie and bad latch even after correction. It’s like people think if you provide good educational information about formula everyone will suddenly stop breastfeeding! It was my last resort in a very emotional time so felt a lot of fear over switching and not a single person offered me any advice, we just used the instructions on the back of the can. Luckily my son (and me!) are doing great with formula.


  6. Jessica Says:

    Thank you for providing this wonderful resource.


  7. Dr. Roy Says:

    Rachel, one would think shaking would indeed eliminate the hot spots. But there are reports of burns, like this one from 1984: Another report ( documented the presence of “hot spots” near the top of the bottles– those authors thought it would be safe to use only if the formula was mixed well and tested before offering it to Junior.

    Oral burns are bad news. I’d be careful.


  8. Ross MacLeod MD Says:

    Dr Roy, when I went through med school (late 60’s) you did not get a ‘passing grade’ in Peds UNLESS you were able to formulate a formula from “Farmers Wife #2” or “Carnation evaporated milk” adding the correct amount of sugar and water diluent.
    Boy have times changed!!!!


  9. Ceridwen Says:

    One advantage of using the drop ins is that they heat much faster with the “place bottle in warm water” method. We found that particularly useful when bottle feeding pumped breastmilk that had been kept in the fridge.

    Once we started feeding formula we preferred to put tap water in an electric kettle and let it heat until the desired temp (usually took less than a minute), then fill the bottle from the kettle and add the powder. No need for any additional warming. For overnight bottles we would add the powder to the bottle and keep the bottle and a thermos with lukewarm water in it next to the bed. When baby woke, just add the water to the bottle, shake, and go.


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