Switching Baby Bottle Nipple Sizes (When & How)

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Is it time to switch your baby's nipple sizes?

Is your baby getting frustrated with the bottle and you’re wondering whether to go up a nipple size? How do you know when it’s time to make the change? Were you even aware there were different nipple sizes and that it could make a difference?

Nipple size is just one of many choices when it comes to your baby’s bottles. Choosing the right size nipple for your baby will make feedings more comfortable and enjoyable for everyone involved. But how do you know which is the right size nipple for your baby and when to move up a size?

Let’s discuss the preferable nipple sizes for formula fed and breastfed (including exclusively pumping) babies, signs it may be time to move up a size, and other reasons your baby may be fussy with the bottle.

Table of Contents

    When To Switch Bottle Nipple Sizes

    The nipple size for your baby’s bottles will depend on if they are formula fed or breastfed, their age, and other readiness cues. Nipple size is essentially the flow rate – how fast your baby can get liquid will depend on the labeled nipple size.

    For A Formula Fed Baby

    For formula fed babies, an age guide for nipple sizes (flow) usually comes with the bottles. The manufacturer should have this guide posted on their website if it didn’t come with the bottles or you no longer have the package insert.

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    The faster nipples are meant for older babies, because they eat more at each feeding and can handle the flow of milk better. Most manufacturers follow this guideline:

    • Slow flow: 0-3 months
    • Medium flow: 3-6 months
    • Fast flow: 6-12 months

    However, age isn’t always the best determinant of nipple size, as all babies are different. There are other signs besides age to indicate when your baby is ready to move up a size, such as:

    • Sucking hard.
    • Flattening the nipple.
    • Getting aggravated (squirming, kicking, pushing the bottle away, etc.).
    • Smacking at the bottle.
    • Taking a long time to feed (30 min. to 1 hour).
    • Eating less at feedings, but getting hungry again soon after.

    If your baby isn’t showing any signs of frustration or taking forever to eat, there is no need to move up a size. But if your baby is showing some of these signs, give the next size up a try and see how your baby does. It’s all about trial and error.

    If you do move up a size and your baby is gagging, coughing, choking, or dribbling milk out of the corner of their mouth, then the nipple flow is too fast and you will need to go back down a size. You may also need to move back down a size if your baby is exceptionally uncomfortable shortly after feedings, as the fast flow may have been too much for their digestive tract (1).

    For A Breastfed Baby

    Experts recommend using slow flow or “newborn” nipples when bottle feeding a breastfed baby. Typically, you should never have to move up a nipple size for a breastfed baby.

    This is because breastfed babies have to work for their milk when at the breast, and breasts usually release milk much slower than a bottle nipple. If you give your breastfed baby a nipple where their milk just flows right out, they may start to get lazy or even refuse the boob. Essentially, the bottle flow should reflect flow during breastfeeding.

    It’s also easy to inadvertently overfeed a breastfed baby when bottle feeding, so caregivers should be sure to mimic breastfeeding as much as possible and feed baby in a more upright position, change positions midway through, and practice paced bottle feeding.

    Even though most breastfed babies should never have to move up a nipple size, in certain cases a faster flow nipple might be a more suitable option. For example, if you have a fast flow and your baby can nurse in five to ten minutes, they may get frustrated with bottles that take 30-45 minutes to finish.

    Assess your own flow and what will work for your baby. If everything is running smoothly, let it be.

    What If I’m Exclusively Pumping?

    Because breast milk digests more quickly than formula and it is so easy to overfeed a baby when bottle feeding, experts still recommend using slow flow or “newborn” nipples even if you’re exclusively pumping. Just like any other breastfeeding mom, feed your baby on demand (not according to a rigid schedule) and follow paced bottle feeding methods.

    Typical nursing sessions last 15-20 minutes, so expect your feedings to take around that same amount of time. Allow your baby plenty of time to drink their bottle and don’t rush through a feeding (2).

    Other Considerations

    If your baby seems unhappy with the current nipple size, but doesn’t respond positively to a faster flow nipple, there may be other factors to consider. You may want to try a different shape (such as an orthodontic or angled nipple), texture, length of nipple, or a different venting system.

    Keep in mind a ‘preemie nipple’ doesn’t necessarily mean it’s slow flow, though for some brands they do. And some brands don’t go by age, but rather label the nipples ‘level 1’ and level 2.’ You’ll need to read the packaging or even check the manufacturers website to get a feel for what these labels mean.
    Headshot of Michelle Roth, BA, IBCLC

    Editor's Note:

    Michelle Roth, BA, IBCLC

    The problem might also not be with the equipment itself. Your baby may be going through a distracted phase, teething, having a medical issue, or unhappy with the temperature of the milk. You could also have high lipase in your breast milk or possibly be misinterpreting your baby’s cues as a sign of hunger (3).


    Keep The Size Right

    Having the right size nipple will make feedings faster, easier, and much more enjoyable for everyone. Nipple size may depend on if your baby is formula fed or breastfed, their age, and other readiness cues.

    Bottle nipple size isn’t a one-size fit all kind of guide, so assess your situation and figure out what will work best for you and your baby. If everything is going smoothly with the current size nipple, then let it be.

    When did you switch nipple sizes on your baby’s bottles? Tell us how you knew it was time to make the change in the comments below, and be sure to share this post with all of your bottle feeding friends.

    Headshot of Michelle Roth, BA, IBCLC

    Reviewed by

    Michelle Roth, BA, IBCLC

    Michelle Roth, BA, IBCLC is a writer, editor, and board-certified lactation consultant for two busy pediatric practices. She is a former La Leche League Leader, Lamaze Certified Childbirth Educator, and Certified Infant Massage Instructor.
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    10 Reader Comments

    1. My 5 week old has been on comfort milk with level 2 teat for 2 weeks due to bad colic. He’s now displaying all of the above signs so we’ve moved him to level 3 (Dr Brown’s) from today to see if that helps. He’s always been a very aggressive eater and flattened the level 1 teats from birth!!

    2. Heather

      What if a level 2 is too small and level 3 too fast ? She shows signs of both.

    3. Narges

      My baby uses a Dr. Brown bottle and takes over 30min to 1 hr with the level 1 nipples. He keeps pushing away to feed. When I use the level 2 nipples, though, milk drains from the side of his mouth but none of the other signs for too fast flow. I’m not sure what to do about it. How do I know what the right size is for him?

      • Team Mom Loves Best

        Hey Narges, thanks so much for reading. It’s possible that your baby is somewhat in between sizes right now. So the 1 is too slow, but 2 is still a bit too far. We suggest waiting and watching to see if he adjusts to the current nipple size. If he begins gagging or seems uncomfortably full after feedings, it might be too fast for him. Let us know how it goes, and all the best!

    4. Jeanet Beatty

      My 7 week old has been on comfort milk with level 2 teat for 3 weeks due to bad colic. He’s now displaying all of the above signs so we’ve moved him to level 3 from today to see if that helps. Is that ok? Thank you

      • Team Mom Loves Best

        Hey Jeanet, if he’s been showing signs of needing a wider teat, then you’ve likely made the right choice. Just watch him for a few weeks and see how it goes. Thank you for reading, and all the best 🙂

    5. Krystle

      Hi, I just want to say how amazing it is to see all this info for exclusively pump-fed baby as I have pumped with all three of my kids since I don’t have the patience for the breast feeding part. There was never so much information available for me with my two older because a mother who strictly pumped was not heard of very often.

      Anyways this was helpful because I was not aware that I didn’t have to go up in nipple size. This makes so much sense to me now because I just automatically did it for my oldest because the doctor said I needed to cause he was too old to be using a new born nipple.

      It makes me feel a lot more confident to know I’m worrying for no reason with my last one since she is almost 3 months and definitely is not ready for the next size nipple. I was stressing out about having to switch her because I know she isn’t ready. It really does make the world of difference to know I don’t have to switch her nipple yet.

      The only thing I am confused about with her is how she is eating less milk and going longer with out feeding. My boys never did that so it worries me she’s not getting enough food. Also for Mama’s that are pumping and need some help, I’m more than willing to give advice even if I might not help that much. I pumped for a year straight with both my boys and am on my year pumping goal with my baby girl. I have experience from making to little milk to making way too dang much 😂.

      • Team Mom Loves Best

        Hi Krystle! It is so heartwarming to read your experience. We truly believe that while breastfeeding is nice and advisable, the most important thing is keeping our little humans alive and well. We’re glad that our website made you feel seen and welcome. Every baby is different, so if your little girl is gaining weight appropriately, then she’s doing well. Please feel free to share some of your tips for increasing milk supply — we’ll happily gobble it up 😀

    6. Kimberly

      Hello, thanks for having such a helpful page! I am exclusively pumping for my five month old, and she is doing well with weight gain and growth, but she has always been on the small side due to genetics.

      We began her with a size 0 nipple at four weeks old when transitioning from nursing. Now at five months, I thought she needed to move to a size 1 nipple because she was smacking during feedings occasionally. Now with the size 1, she is spitting up a lot and also is distracted while eating and taking forever to finish her bottle.

      Should I go back to a size 0 nipple? Would I ever need to change to a size 1?

      Thank you.

      • Team Mom Loves Best

        Hi Kimberly, thank you so much for reading. We would advise you to be patient with your lovely girl. As she gets older, she likely will move to a higher nipple size, but follow her lead. So if she’s spitting up, it might be too much for her. It might be worth trying the 0 again and seeing how she responds. Let us know how that goes, please? We would appreciate it 🙂 All the best.

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