Let’s talk about supplementing. It’s way more common than you think. Supplementing is a fact of life for many mommas, but can also be the key to prolonging your pumping journey!
How? Read on to find out:
*This post is NOT sponsored by any formula brands, nor is any specific brand mentioned/suggested/promoted within this post*

What is “supplementing?”
Let’s start with the basic idea of supplementing. When the breastfeeding community talks about “supplementing,” we are referring to something that is adding to your infant’s diet of breastmilk to fill any nutritional gaps. We also call this “combo feeding.” This is most commonly referring to supplementing a lowered supply of breastmilk with formula, but can mean supplementing with donor milk, solid foods when the baby is older, or even nutritional supplements like vitamins and minerals prescribed by your child’s pediatrician. For this blog post, we are going to focus on supplementing with formula.
Coming to terms with supplementing
The need to supplement can leave mommas feeling guilty about not being able to provide a complete diet of breastmilk for their baby. I get it, I’ve been there. Keep in mind, even if you can’t provide 100% breastmilk for your baby, they are still getting 100% of the benefits of your breastmilk. Read that again, because it’s true. That amount still matters. (For example, did you know that one teaspoon of breastmilk contains up to 3 million germ-killing cells? Wow!) Still, it can be hard to start supplementing. There can be feelings of failure. There can be feelings of guilt and grief. Let yourself feel your feelings, because they matter. Then, try reframing your mindset about supplementing. Formula was scientifically designed to help infants thrive. A mindset shift that helped me personally was this: Soon, there will be lots of things your baby will eat that you didn’t personally create with your body. Do you give yourself a hard time because you can’t create bananas, bread, or broccoli with your body? Of course not! Just group formula in with all the new foods that will nourish your baby.
I promise, there are so many silver linings to supplementing!
The benefits of supplementing
- Supplementing can help improve baby’s bilirubin levels to combat jaundice.
- Supplementing can help while a momma is actively working with a lactation professional to improve nursing or pumping.
- Supplementing under a doctor’s guidance can help a baby who is struggling with weight gain.
- Supplementing helps a momma with low supply keep offering breastmilk.
- Supplementing can help mommas reach their breast pumping goal.
- Supplementing can help momma ease up on her pumping schedule and potentially pump longer than anticipated because it feels more sustainable!
- By combo-feeding, you can ensure baby is still getting the benefits of your breastmilk, no matter what amount you are able to provide. Think of it as the most personalized vitamin you can give them!
Keep in mind…
- Replacing a feed with formula can negatively affect your supply if you aren’t pumping in place of a nursing session.
- If you are supplementing while “waiting for your milk to come in,” you should be actively working to bring on the next stage of lactation by regularly pumping or nursing to bring on that mature milk.
- If you are separated from baby, it is wise to pump every 3 hours to protect your supply.
- It is always advised to work closely with a lactation professional to meet your feeding goals.


What should I supplement with?
Ideally, supplementing with breastmilk would be “best.” Using your own freezer stash of milk would be great, but that’s not feasible for everyone. Supplementing with donor milk would also be great, but can be extremely pricey to purchase from milk banks. Some mommas are able to link up with family or a trusted friend who are willing and able to donate breastmilk. Others find local mommas on a HumanMilk4HumanBabies or EatsOnFeets facebook groups, both of which are considered “informal” mother-to-mother milk donation platforms that do not screen their donors like milk banks do.
If breastmilk is not available, your other choice is to supplement with formula. Despite clever marketing, there is no formula brand that matches the nutritional composition of breastmilk, it’s just not possible. Before buying a large amount of formula, I suggest seeing if your baby takes it without argument/difficulty. If you need a specialty kind, work with your pediatrician to find the ingredients best for your baby’s unique needs. My colleague Erin, the “Baby Feeding Coach” has a great page on understanding a formula label HERE. For a deeper dive, trust my friend Bridget Young, PhD, the “Baby Formula Expert” advice found HERE.
How do I supplement with formula?
There are many ways to use formula in supplementary feeding. Some mommas choose a specific time of day, such as nighttime feeding by a helpful partner, or when their baby is at daycare. Some pumpers alternate feeds between breastmilk bottles and formula bottles. Another choice is to offer a partial feed of breastmilk and supplement the rest with formula. Some mommas choose to do this with two separate bottles, or feeding the breastmilk first, then putting formula in the empty breastmilk bottle to finish the feed. Others choose to mix the formula and breastmilk together in one feeding bottle.
Try easing into formula introduction when baby is in a good mood. An overly tired or hungry baby is in no mood to try something new. Once you know that baby will accept the bottle of formula, you can gradually increase how much you offer them.

Can I mix breastmilk and formula?
The short answer is yes. Yes, you can mix breastmilk and formula as long as it is done safely. Breastmilk should never replace the water used to mix up powdered formula. If you plan to mix breastmilk and formula, prepare the formula as directed, and then add breastmilk to it. According to Dr. Bridget Young, there is evidence of proteases (enzymes that break down protein) in breastmilk helping to digest the proteins in formula, which can result in easier digestion for baby. This will happen if you feed the breastmilk and formula in the same bottle, or back-to-back in the same feeding.
Are there any reasons NOT to mix breastmilk and formula? You should be sure your baby does not reject the formula you are offering. If they reject the bottle, you may be wasting that liquid gold (a.k.a your precious breastmilk!) Another reason is that once baby has started feeding from a formula bottle, you need to use it within an hour. With breastmilk, that rule is use within 2 hours.
Storing prepared formula
Once prepared, formula should be used within 24 hours. Mommas who prepare a pitcher of formula in advance should use the formula within 24 hours. If baby begins to drink from the bottle, it is advised to use that bottle within 1 hour, without putting it back in the fridge to save for later in the day.
Sources:
- Healthline- “How to Supplement Your Breastfed Baby’s Feedings with Formula”
- BabyCenter- “How to Supplement With Formula When You’re Breastfeeding”
- Cleveland Clinic- “Feeding Your Baby: How and When to Supplement with Formula”
- WebMD- How to Supplement with Formula
- Nemours Kids Health- “Breastfeeding vs. Formula Feeding
- The Bump: Combo Feeding Baby: How to Supplement with Formula


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