Supplementing with Formula: The Guide Every Mama is Looking For

Lots of breastfeeding mamas begin supplementing with formula at some point in their breastfeeding journey. This can happen for a number of different reasons, ranging from weight gain issues in baby, to mama’s mental health, and a million things in between!

I personally supplemented breastfeeding with formula for both of my boys. And when I finally did it – I had such a feeling of relief! If you know me, you know that I am all about supporting moms with breastfeeding through education and resources. But I’m also solidly on team fed is best.

I know all too well the struggles of low supply and the mental drain that breastfeeding can have on some mothers. I also remember the challenges of navigating how to supplement with formula and where to even start. So many resources were focused on sticking it out, and I became wracked with guilt at the thought of even buying formula.

With all of that said – I want to provide you with a guide to supplementing with formula – for WHATEVER reason you are deciding that this is right for your family. Because ANYTHING that can make this early motherhood thing a little bit easier deserves our time and attention.

So let’s jump right in!

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Why your pediatrician might recommend supplementing with formula

Your pediatrician might recommend, or even go as far as to basically require supplementing with formula if your baby is labeled “failure to thrive”. A term, I personally kind of hate. But basically, it means that baby is either gaining weight much slower than expected, not gaining, or losing weight by the time they are 10-14 days old.

It is actually considered pretty normal for babies to lose some weight in their first days of life. And this is true for breastfed and formula-fed babies.

A weight loss of 7-10% of baby’s total weight in the first 5-7 days of life is considered normal in breastfed babies. But we expect to see them back up to their birth weight between days 10-14. For formula-fed babies, the weight loss is usually around 5%.

If you reach day 14 and baby is not gaining or has not reached their birth weight, this is when a conversation about supplementing can start. This can be tough for a lot of mamas, so if you are currently in this situation, please know I have been there, and I am sending so much love.

Weight gain issues in newborns

Often, weight gain issues are caused by an underlying issue that can be resolved – and it’s not always about supply! Figuring out the why behind your baby’s breastfeeding challenges can be key if you DO desire to continue breastfeeding or want to go back to exclusive breastfeeding at some point.

I hear from mamas who say that their baby was labeled failure to thrive, and they were told to supplement with formula, but then no explanation or steps were taken to figure out the WHY. So this may take some advocacy on your part.

If your pediatrician doesn’t seem to be super helpful or responsive, or even if they are, I highly recommend working with a certified lactation consultant. They can offer a wealth of knowledge and specialized advice and become invested in your unique situation!

Here’s a list of underlying issues that can be associated with breastfeeding challenges/weight gain issues in baby. Please note this is not an exhaustive list and is not meant as a means of diagnosis! It’s more of a jumping-off point to give you an idea of just how complex this can be!

  • Tongue or lip ties
  • Poor latch
  • Other anatomical anomalies in baby
  • Allergies or intolerances in baby
  • Birth injuries that cause pain during feeding for baby
  • Infections such as thrush causing pain during feeding for baby
  • Low milk supply
  • Reflux
  • Malabsorption of nutrients in baby
  • Developmental delays

(Source 1, Source 2, Source 3)

Other reasons why mamas start supplementing with formula

In other cases, the decision to supplement isn’t due to weight gain or breastfeeding issues. And these reasons are equally as valid and important to honor!

I already shared that my reasons for supplementing with my first were rooted in weight gain issues, but with my second, it was fueled by my own mental health and peace of mind. Once I finally allowed myself to supplement, I only wondered why I hadn’t done it sooner!

Here are some reasons you might be considering supplementing with formula. If this is you, let me just say that I stand behind you 100%!

  • Breastfeeding/pumping is causing stress or stealing the joy from your motherhood experience
  • You are struggling with sleep deprivation and want some support for nighttime feeds
  • Your partner wants to help with feeding baby and you are not interested in or no longer wish to pump to make that happen
  • Your mental health is suffering due to scheduling pumping and worrying about making enough milk for baby
  • You are feeling touched out from on-demand breastfeeding and need a break
  • You are struggling with a perinatal mood disorder such as Postpartum Depression or Postpartum Anxiety, and breastfeeding is triggering for you
  • You want to leave baby for extended periods of time without the logistics of pumping
  • You recently went back to work and are seeing a decrease in supply
  • You are experiencing a decrease in supply for any other reason
  • You just don’t want to exclusively breastfeed anymore – for any reason!

Podcast Episode: Formula Can Be Your Friend with The Formula Mom

How to Supplement with Formula?

So, are you wondering where to even start?! I remember that once I got passed the #momguilt of deciding to supplement, I felt super overwhelmed as to what my next step was.

If you’re like me, you are hoping to continue breastfeeding some of the time, so it’s important to you that you don’t inadvertently diminish your supply. Maybe you’re also concerned about baby preferring the bottle over the breast? Or wondering exactly when to give formula, and when to breastfeed? And can you mix the two? I’ve got you, mama!

Okay, so there are basically three main approaches to supplementing that mamas take:

  • Combination feeding at every feed
  • Formula feeding in place of a few select feeds
  • Exclusive (or near-exclusive) bottle-feeding where you mix formula and breastmilk

Of course nothing in this world is 100% black and white, so you may wind up doing a combination of two or all of these methods! Deciding which one is right for you will also depend a lot on your goals.

For example, if you’re supplementing due to weight gain issues, but hope to get back to exclusive breastfeeding, your approach is going to be different than if you are feeling like you need a break from nursing or want to wean from pumping.

Let’s get into the details.

Breastfeeding followed by formula at every (or most feeds)

This approach (or approach 3) is most popular with mamas that are using formula to supplement a low supply, but are hoping to bring their supply up and resume exclusive breastfeeding. Those aren’t the only moms using this approach, but it’s definitely most common for that purpose.

In this approach, you will always start baby’s feeds out on the breast. Aim to give baby both sides, and then immediately follow the feed with a formula bottle.

For an extra supply boost, if low supply is something you’re working on, pump while baby is getting their bottle, or very shortly after you nurse baby. This ensures that your breasts are completely drained, and will signal to your body to make more milk.

This strategy is known as triple feeding. It’s a very effective way to resume exclusive breastfeeding but can be very mentally and physically exhausting. Amanda, the certified lactation consultant behind @exclusive_pumping (article linked above), has SO many excellent resources to help you with this.

Related: 30 Methods to Increase Milk Supply

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Formula only at certain feeds

This approach to supplementing works really well for mamas that want or need to spend time away from baby, and for mamas that simply want a break from exclusive breastfeeding! With this approach, certain feeds each day are replaced with formula.

Choosing which feeds to replace will depend a lot on your needs and unique schedule. But it’s important to keep in mind that if you don’t pump while baby gets their formula bottle, your supply is going to decrease.

This is totally okay if you are planning to kind of permanently supplement (or move toward exclusive formula). However, if you think you may want to resume exclusive breastfeeding or are hoping to build a stash of breast milk, then pumping is important.

Another thing to note – for many moms it’s beneficial to replace the same feeds each day with formula. This can help you avoid issues like engorgement, clogged ducts, or even mastitis. This might be especially important for mamas that already have oversupplies or seem to be prone to clogged ducts.

Related: Six In-Depth Breast Pump Reviews

Formula and breastmilk combined in a bottle

If you are an exclusive pumper or do a combination of feeding at the breast and feeding breast milk from a bottle this is a great approach for you. By adding formula to a breast milk bottle, you can effectively increase the calories and amount of milk for baby.

This works really well if you simply don’t pump enough for baby but still want them to get some breastmilk. This can also be an effective way to get baby to take a formula bottle if they aren’t too keen on it. Breastmilk has a more familiar taste to them!

How to do it?

  • You should mix and prepare the formula bottle first and then add in the breast milk
  • You are not supposed to add powdered formula directly to breast milk
  • If you are making the bottle now for use later, wait to add the breast milk right before feeding and make sure both the formula bottle and breast milk are chilled before combining.

The one big drawback to this method is that if baby doesn’t finish the bottle, you may end up wasting some of your precious breast milk! Formula bottles can only be re-used within 1 hour at room temperature. For this reason, you may want to bottle feed your pumped milk separately.

Interestingly, the international breastfeeding association La Leche League recommends against this practice.

What about supplementing at nighttime?

If your goal is longer stretches of sleep, your partner can certainly give baby a formula bottle overnight. Like I mentioned earlier, when you are replacing a feed, it’s beneficial to do it around the same time (or time frame) each night to avoid any issues for you (like engorgement or clogged ducts).

Pre-measuring formula and using a formula dispenser is a great way to make the job of preparing a formula bottle at night easier on whoever is doing the feeding.

FAQs about supplementing breastfeeding with formula

Okay, so now that we’ve gone through the different methods of supplementing, and a bit about the why, I thought I’d dive into some FAQs. Taking on formula feeding can actually feel really stressful! Hopefully, these answers (and mentioned resources!) can erase some of that for you!

What’s the best formula for breastfed babies?

Gosh, this is the million dollar question, isn’t it? There are so many dang options out there! And after extensive research, the one answer I’ve come up with, is that there is no blanket option that is best for every baby. Your baby’s unique needs, your goals, your budget, and more all play a role in choosing the right one for you.

So, what’s a mama to do? Well, my friend Mallory over at the Formula Mom is single handedly addressing this problem! She has a resource that will give you personalized formula recommendations based on your unique situation called the Fast Track Formula Finder.

Head on over here to learn more about her Fast Track Formula Finder! It’s an absolute must, and she was literally a godsend to me when I was trying to figure out the right formula for my second, Ryland, who has some food intolerances.

You can also check out our article, Organic vs. Non-Organic Formula: What’s the Deal?

How to introduce formula to my breastfed baby? How to introduce a bottle to breastfeeding baby?

When it comes to introducing formula to your breastfed baby, the most important thing to learn is how to do paced bottle feeding. This is basically a way of bottle feeding your baby that mimics breastfeeding by following baby’s cues on when to start and stop.

It has many benefits to baby such as preventing overfeeding, preventing a preference for the bottle, and promoting awareness of hunger/satiety cues. To learn more details on how to do this technique, check out our article, The Complete Guide to Paced Feeding.

A few additional tips to help with the introduction:

  • Mixing breastmilk with formula can help make the introduction smoother, especially if baby is refusing formula
  • If baby is refusing the bottle, you can use syringes/droppers to feed newborns, and KellyMom even recommends cup or spoon feeding while they adjust
  • Mimic the breastfeeding experience as much as possible: do skin-to-skin and “switch sides” halfway through by re-positioning baby

Some mamas swear that certain bottles can help your breastfed baby transition, too! Some of the most popular bottles for breastfed babies are the Como Tomo, Tommee Tippee, and the Munchkin Latch.

Can you mix breast milk and formula?

Yes, you can! So, we talked about this a bit above, but you can mix breast milk and formula. Just be sure to wait to add the breastmilk after you prepare the powdered formula per the instructions on the can.

And if you’re going to be giving the bottle later, wait to add the breastmilk right before use. In this case, both the breastmilk and prepared formula bottle should be chilled and then heated after they are combined.

How long can formula sit out?

I included this question because if you are new to formula you probably don’t know this! Just like breastmilk comes with its own set of safe storage guidelines, so does formula feeding. Here’s a little rundown of what you need to know from the CDC:

  • Use prepared infant formula within 2 hours of preparation (at room temperature)
  • Use prepared infant formula within 1 hour of when feeding begins (if the bottle wasn’t finished)
  • A prepared formula bottle that baby has not fed from can be stored in the fridge for 24 hours

Supplementing with formula until milk comes in?

Some moms are confused about whether they need to supplement with formula while waiting for their milk to come in. In most cases, the answer is no!

Before your breast milk comes in, your body is producing baby’s first food, called colostrum. Colostrum provides baby with everything they need in their early days of life and can sustain them as you wait for your milk to come in.

What’s more, the act of putting baby to the breast to feed every 2-3 hours (or more often!) immediately after birth is what will help signal to your body to make milk, and will help get your supply off on the right foot!

As always, remember that only your provider, pediatrician, or a certified lactation consultant can speak to your unique situation.

What about breastfeeding only at night and supplementing during the day?

Okay, so some moms are hoping to supplement during the day, but actually prefer to exclusively breastfeed at night because of convenience, or they enjoy the closeness and snuggles of nighttime feeds.

If this is you – then know this is totally possible! You can certainly supplement during the day and still aim to breastfeed only at night if that’s what you wish.

The only caveat here is that If supply is currently an issue, and/or baby is having issues with weight gain, it may be necessary to follow nighttime nursing sessions with a formula or breastmilk bottle until your pediatrician or lactation consultant advises otherwise.

Be sure to talk to one of those professionals about your unique situation to making this work!

Should I supplement with formula?

The decision to supplement with formula may be one that is personal, or it might be for baby’s ability to thrive. But whatever the situation is, know that you don’t have to go through this process alone! There is so much more information and guidance out there to help you navigate the waters of supplementing than there was even 5-10 years ago.

The best thing you can do is find a professional support person that will help you achieve your unique goals. Whether that’s getting back to exclusive breastfeeding, maintaining enough of a supply to both formula feed and breastfeed, or slowly transition over to exclusive formula.

The best source of support is going to be your baby’s pediatrician and a certified lactation consultant. There are also a number of excellent online resources and websites to turn to.

Here are some to get you started:

  • The Formula Mom to help choose the right formula, and over on Instagram @theformulamom for great, practical formula feeding advice and solidarity
  • Exclusive Pumping is a website dedicated to information on exclusive pumping, but she also has a wealth of info related to supplementing, and how to build up your supply if you wish to exclusively pump
  • Kelly Mom has a great article about partial weaning and combination feeding

Do you have a question about supplementing with breast milk that we didn’t cover? Want to share your story about how you decided added formula was the right choice for you? Be sure to leave a comment below!

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Liesel Teen, BSN-RN
Founder, Mommy Labor Nurse

Meet Liesel Teen

Hi there. I’m Liesel!

As a labor and delivery nurse, I’ve spent countless hours with women who felt anxious — even fearful — about giving birth. I want you to know it doesn’t have to be that way for you!

When you know what to expect and have the tools to navigate the experience, you’ll feel confident and in control.

I believe you deserve a better birth — no matter how you deliver.