What Bottle Nipple Size Should a Newborn Use? What I Learned With Two Babies

Before I had my first baby, I had no idea bottle nipple sizes were even a thing. I knew I needed bottles, obviously, but I didn't realize those bottles could come with different nipple flow rates or that I would eventually have to figure out when to move from one size to another.

After two babies, I've now used everything from an Ultra-Preemie nipple to a Size 2. I've also learned that moving up isn't always a straight line. Sometimes a slower nipple works better, and sometimes you may even move up a size and then decide to go back down.

So, what bottle nipple size should a newborn use? There isn't one nipple size that's right for every newborn, and nipple sizing can vary by bottle brand. With both of my babies, though, I had success starting with a slower-flow nipple and increasing the flow based on how they were actually feeding rather than simply following their age.

Here's what that looked like for us.

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What Bottle Nipple Size Should a Newborn Use?

The best bottle nipple size for a newborn depends on the baby, the bottle brand and how they're feeding. Rather than assuming every newborn should start with a particular numbered nipple, I learned to pay attention to how long bottles were taking and whether my baby seemed comfortable with the flow.

I used Dr. Brown's bottles with both of my babies. I originally chose them because they're designed to reduce colic, spit-up, burping and gas, and after having a good experience with them with my first baby, I continued using them with my second.

With my full-term son, I started with a Dr. Brown's Preemie nipple. With my premature daughter, we started even slower with an Ultra-Preemie nipple in the NICU.

Their feeding journeys were very different, but starting slowly worked well for both of them.

Why I Started My Full-Term Newborn With a Preemie Nipple

My son wasn't premature, but my doula recommended that we start with a Preemie nipple because I planned to breastfeed.

We had actually talked about bottles before he was born, and she suggested the slower flow because it could be more comparable to the slower flow he would experience while breastfeeding. I followed her recommendation and had a good experience with it.

He stayed on the Preemie nipple for approximately his first month before we moved him to a Size 1.

Knowing what I know now, I would personally start with the slower-flow nipple again. It worked for us, particularly while I was trying to establish breastfeeding, and I liked being able to increase the flow when my baby showed me that he was ready rather than starting too fast.

That doesn't mean every full-term newborn needs a Preemie nipple. This was simply what worked for my babies, and feeding needs can be very individual. If you're starting with a slower flow too, I wrote more about how long babies use Preemie nipples and what made us decide it was time to move up.

My Preemie Started With an Ultra-Preemie Nipple

My second baby's experience was completely different.

She was born at 33 weeks and spent just under two and a half weeks in the NICU. The NICU specifically chose an Ultra-Preemie nipple for her because she was premature and still learning the coordination required for bottle feeding.

That experience also taught me just how many nipple-flow options existed.

With my first baby, I knew about Preemie and then moved directly to Size 1. I didn't even know there was a Transition nipple between Preemie and Size 1.

With my daughter, we moved much more gradually. She started with Ultra-Preemie in the NICU, transitioned to Preemie around one month old, and later used a Transition nipple before eventually moving to Size 1.

If you have a premature baby, I would follow the guidance of your NICU or feeding team rather than trying to determine nipple flow based on age alone. Preemie feeding is its own experience, and our NICU team was instrumental in determining what worked for our daughter. I share our entire progression through Ultra-Preemie, Preemie, Transition and Size 1 in my guide to preemie bottle feeding.

How Do You Know If a Bottle Nipple Flow Is Too Fast?

This was one of the biggest things I had to learn. The number printed on the nipple matters much less than what your baby is doing while they're drinking.

For us, some of the signs that made me question whether a nipple was too fast were coughing or choking during the bottle and increased spit-up that sometimes seemed almost like throwing up.

If feeding suddenly seems more difficult after changing nipple sizes, I wouldn't assume that you have to stick with the new size just because your baby has technically reached the recommended age for it.

I learned that firsthand with my daughter.

How Do You Know If a Bottle Nipple Flow Is Too Slow?

The opposite can happen too.

One of the clearest signs for me that the flow might be getting too slow was when a bottle suddenly started taking much longer to finish than it typically had. I could also see my babies sucking much more aggressively as they tried to get milk out.

That's usually when I started considering whether it might be time to try the next nipple size.

Instead of changing nipple sizes automatically at a certain age, I found it much easier to watch how my baby was actually feeding.

You Don't Have to Keep Moving Up

This is something I definitely didn't understand as a first-time mom.

Nipple sizes aren't necessarily a perfectly linear progression where you move from one size to the next and never look back.

With my daughter, I actually went back down a nipple size after moving up. Her daycare raised concerns about the flow and recommended trying the slower nipple again, so we did.

That experience made me much less concerned about following a rigid nipple-size schedule. If a faster nipple isn't working well, you can talk with your pediatrician or feeding professional about whether going back to a slower flow makes sense.

What Age Should You Change Bottle Nipple Sizes?

This is where I think bottle nipple sizing gets confusing. Bottle brands may provide age ranges for their different nipple levels, but babies don't all feed the same way. My two certainly didn't.

My son started with a Preemie nipple and moved to Size 1 at around one month old. My daughter started on Ultra-Preemie because she was premature and progressed much more gradually through the different flows.

I found it more useful to think of the manufacturer's age recommendations as a reference point rather than assuming that reaching a certain age automatically meant it was time to size up.

How your baby is actually handling the bottle matters.

Does Bottle Nipple Size Matter If You're Breastfeeding?

This was the reason I started thinking about nipple flow in the first place.

My doula recommended a slower-flow Preemie nipple for my son because I planned to breastfeed, and that approach worked well for us. If you're combining breast and bottle feeding, a lactation consultant or other feeding professional can help you determine which nipple flow makes sense for your baby and your feeding goals.

I wouldn't assume that you need to move to a faster nipple simply because your baby is getting older.

What I Wish I'd Known About Bottle Nipples as a First-Time Mom

I wish someone had simply told me that nipple sizes existed.

That sounds so basic now, but when I was pregnant with my first baby, I genuinely didn't know that bottles had different nipple flows. I didn't understand the difference between slower and faster nipples, how you knew when to change them or that the "right" nipple wasn't necessarily determined by age.

By my second baby, I had experienced Ultra-Preemie, Preemie, Transition, Size 1 and Size 2 nipples. I had also learned that you can move up, decide it isn't working and move back down.

My biggest takeaway is that you don't need to rush through nipple sizes.

Start with what works for your baby, pay attention to how they're feeding and adjust when their feeding behavior tells you something needs to change.

FAQs About Newborn Bottle Nipple Sizes

Should a newborn use a Preemie or Size 1 nipple?

It depends on your baby and the bottle brand you're using. My full-term son started with a Dr. Brown's Preemie nipple based on my doula's recommendation because I planned to breastfeed. Other newborns may do well starting with Size 1. If you're unsure, ask your pediatrician, lactation consultant or feeding specialist which flow is appropriate for your baby.

Can a full-term baby use a Preemie nipple?

My full-term baby did. We chose the slower flow because I planned to breastfeed, and he used the Preemie nipple for approximately his first month before moving to Size 1. That was our individual experience rather than a rule for every newborn.

How do I know when to move my baby up a nipple size?

For me, the biggest clues were bottles beginning to take much longer than usual and seeing my baby suck aggressively while trying to drink. Rather than sizing up based only on age, I paid attention to changes in how my babies were feeding.

What happens if the bottle nipple flow is too fast?

I noticed coughing, choking and increased spit-up when the flow wasn't working well. If your baby is struggling during feeds or you're concerned about their feeding, talk with your pediatrician or feeding professional.

Can you go back down a bottle nipple size?

We did. After moving my daughter up, her daycare recommended that we try the slower flow again. Going up a nipple size doesn't mean you can never go back if the faster flow isn't working well.

Are bottle nipple sizes the same across brands?

No. Nipple names, numbers and flow rates can vary between bottle brands, so check the manufacturer's guidance for the specific bottles you're using rather than assuming a Size 1 from one brand is identical to a Size 1 from another.

The Bottom Line

If you're standing in your kitchen wondering which tiny bottle nipple you're supposed to use, I get it. I didn't even realize this was something I'd have to figure out before I had my first baby.

Starting with a slower flow worked well for both of my babies, although for very different reasons. My full-term son started with a Preemie nipple while I was establishing breastfeeding, while my premature daughter started with an Ultra-Preemie nipple under the guidance of her NICU team.

The biggest thing I've learned is that nipple size isn't something you necessarily need to change just because your baby reaches a certain age. Watch your baby, pay attention to how feeding is going and don't be afraid to ask for help or adjust the flow when something doesn't seem right.

Medical note: This article shares my personal experience and is not medical advice. Bottle feeding can be different for every baby, particularly for premature babies or babies with feeding difficulties. Talk with your pediatrician, lactation consultant or feeding specialist if you have questions about the appropriate nipple flow for your baby.