When To Change Bottle Nipple Flow Size?

It often seems that you’ve just settled into a predictable parenting routine when your child reaches a new developmental milestone that throws your whole system off. Case in point: After several weeks or months of happily taking their bottle feedings, your infant suddenly seems to dislike mealtime and have a particular hatred for their bottle.

What’s going on here? Will your child ever eat again? Fortunately, the answer may be that your child is simply trying to communicate that they’ve outgrown the need for a slow milk flow rate and are ready for faster delivery.

Baby bottles with different nipple sizes

Let’s take a look at some of the signs that indicate when to change bottle nipple flow size, a few potential concerns to be aware of and how you can make the transition safe and simple.

What is Nipple Flow?

The size of the nipple opening determines the rate that milk flows out of your baby’s bottle. Each baby goes through a series of stages in the process of growing up, and their feeding needs and preferences will likely change depending on their age, developmental level and physical capabilities.

Most nipples will fall into one of three general flow categories.


A slow flow nipple has the smallest opening and allows milk to pass through at the lowest volume. Slow flow nipples may also go by a few other names depending on the brand.

  • Preemie
  • Newborn
  • 0+ months
  • 0-3 months
  • Level 1


Medium flow nipples have a slightly larger opening that allows your baby to drink milk at a faster pace. Some brands may also refer to their medium flow nipples in a few other ways.

  • 3+ months
  • 3-6 months
  • Level 2
  • Level 3


These nipples have the largest opening available and allow milk to pass through at the fastest rate. Fast flow nipples may also go by any of the following names.

  • 6+ months
  • 6-12 months
  • 9+ months
  • Level 4
  • Y-cut

If you’re interested in giving your child the fastest flow possible or your health care provider recommends thickened feedings for your child, Y-cut nipples are likely to be your best bet. Rather than a simple hole in the nipple tip, Y-cut nipples have three tiny slits that open simultaneously to provide a large opening.

Why Using the Appropriate Nipple Flow is Important

Everyone wants to feel calm and relaxed while they eat, and your child is no exception. A nipple that delivers milk either too slowly or too quickly can make it hard for your child to feed comfortably and efficiently.

If the flow is too slow, your baby must use extra energy to draw the milk out at a satisfying rate. To put it in perspective, picture how difficult you would find it to try drinking a milkshake through a narrow straw.

On the other hand, your baby may struggle to keep up with a milk flow that’s too fast. We probably don’t encounter this situation very often as adults, but you might be able to imagine how your child feels if you’ve ever had to rush through a whole meal in just a few minutes.

When your child consistently feels either frustration or stress at mealtime, they may start to reject part of or all of their feedings. Over the long term, their nutrition and growth may suffer from a lack of nutrients.

Signs Your Baby Needs a Faster Nipple

Generally speaking, slow flow nipples are designed for babies under three months of age, medium flow nipples for babies between three and six months and fast flows for babies over the age of six months. While the suggested age ranges can provide a helpful guideline, your child’s developmental level, preferences and feeding routine should ultimately determine the nipple flow that you choose.

One of the most common signs of a too-slow flow is the length of time your child needs to finish their bottle. Even though normal feeding durations vary based on your child’s age, most babies should be able to finish a bottle in less than 30 minutes. If your child’s meals gradually or suddenly start to take longer than half an hour, it may be time to make the switch.

Here are some other signals that your child may be ready for a faster milk flow.

  • Your baby takes several sucks before swallowing
  • Your baby appears frustrated or gets fussy during feedings and may slap or hit the bottle
  • Your child frequently unlatches and re-latches
  • Your baby sucks so forcefully that they flatten the nipple
  • Your child bites or pulls at the nipple
  • Your baby doesn’t finish their bottle but shows hunger signs a short time after feeding

Potential Problems with Fast Flow Nipples

While a faster milk flow may be the solution to your feeding challenges, it can also cause some problems of its own. Be vigilant for these issues, and consider going back to a slower flow if problems persist.


If the milk flows too quickly, your child may struggle to safely swallow the increased volume coming their way. When your child is unable to produce effective swallowing motions with every suck, milk may accidentally make its way into the lungs rather than the stomach.


When the milk is flowing quickly, your child may be more apt to overlook their natural fullness cues. If your child has an overfilled stomach, you may have to deal with the short-term consequence of increased spitting up. Additionally, chronic overfeeding could also lay the foundation for a lifetime habit of overeating.

Discomfort from gas or indigestion

When your baby swallows milk more quickly, there’s a greater chance that they’ll also swallow more air. Trapped air in the digestive tract can lead to upset tummies and uncomfortable gas.

What Nipple Flow is Best for Breastfed Babies?

Drinking milk from a bottle requires a completely different tongue position and sucking technique than your baby uses to nurse, and it’s usually far easier for babies to draw milk from a bottle than from the breast. Babies are smart, and once they realize that eating from a bottle takes less work, they can develop a preference for bottle feedings and start to reject the breast.

No matter the age or developmental level of your breastfed baby, a slow flow nipple is typically the best choice since it is the closest match to a mother’s milk flow. Especially if you want to continue nursing your child directly from the breast as their primary mode of feeding, combining the paced bottle feeding technique with a slow flow nipple that mimics the natural milk flow from mom can make bottle feeding a bit more challenging for your baby and help maintain the nursing relationship.

What if I’m Exclusively Pumping?

Even though you’re not attempting to maintain direct nursing habits, it’s still a good idea to use a slow flow nipple if you exclusively feed pumped breast milk.

Slow flow nipples give your baby the chance to eat at a slower pace and experience natural fullness cues, so it’s easier to feed your baby the right amount of milk for their needs. In addition to avoiding overfilling your baby’s tummy, you may also be able to avoid pumping more than you actually need to.

What Nipple Flow is Best for Bottle-Fed Babies?

While breastfed babies will probably do best with slow flow nipples, formula-fed babies will typically progress through two or more different flow rates as they grow and mature.

Always use a slow flow for newborns and babies up until the age of around three months. During this phase of development, your child is still working on coordinating their sucking and swallowing movements, so a slower flow is safest until they reach a greater degree of mastery.

Once your child is about three months of age, follow their cues as to when they’re ready for a faster milk flow. Use the nipple packaging to determine the level of flow each nipple allows, and progress only one flow level at a time to give your child a chance to ease into a faster flow rate.

How to Make the Change to a Faster Flow

Now that we’ve covered the why and when of switching to a faster nipple flow, let’s take a look at how you can make the transition as smooth as possible for both you and your baby.

Watch Your Baby Closely

Just as your baby’s cues should be your guide in deciding when to try a faster flow, your child should also dictate how you go about introducing a more advanced nipple.

Carefully observe your child’s reaction to the new nipple, and be alert for the following signs that your baby is having a hard time managing a faster milk flow.

  • Milk dripping out of the corner of your baby’s mouth
  • Gulping
  • Forceful swallowing
  • Coughing
  • Gagging
  • Refusing feedings

Allow Extra Time for Feedings

Although one of your main goals in switching to a faster flow may be to decrease the length of your child’s meals, plan to spend a little extra time at each feeding while your child is in the adjustment phase.

Give your baby the chance to explore the new flow rate and take their milk at their own pace. Additionally, allow for frequent breaks to give your child a chance to rest or catch up to the faster flow.

Introduce the Faster Flow Slowly

Offer the new nipple at just one meal a day, preferably at the feeding where your child has shown the most frustration in the past.

For instance, if your baby usually seems to be the hungriest and most impatient for their morning feeding, that might be the ideal time to introduce a faster flow. Keep adding more fast-flow feedings until you’ve completely made the switch.

Try Different Nipple Styles

Don’t despair if your baby doesn’t seem to take to the new flow level right away. As long as they aren’t choking or struggling to keep up with the flow, give your baby several chances to adapt to the new nipple.

If you’re still running into feeding difficulties after a few days, try some different nipple styles before you go back to your previous flow.

Nipple Materials

Most nipples are either latex or silicone, so make sure to try at least style one in each material to see if your baby displays a preference.

Nipple Shapes

Nipples come in three basic shapes, and each one offers specific benefits.

  • Orthodontic nipples have a flattened end that more closely resembles a mother’s body
  • Angled styles have an upturned tip that conforms to the shape of your baby’s mouth
  • Vented nipples may help prevent gas by using a small hole that draws air into the bottle as your baby drinks milk

You may also want to try a slower flow and a faster flow in a few nipple shapes to find that one that works best for your baby.


You and your baby stand to gain much by making the switch to a faster nipple flow, but only if your baby shows true signs of readiness. Fortunately, most babies will give pretty obvious signals that they’re ready for a change. However, keep in mind that there’s also nothing wrong with sticking to a slow flow for as long as your child is content to use it, even if that means you never move up for the entirety of your child’s bottle-feeding days.

Your baby’s cues will be your best guide as to when it’s the right time to switch to a faster nipple flow and how to make the actual change, so follow their lead, be patient and don’t be afraid to try a few different options.

Now it’s your turn to share! How did you know when it was time to move on to a faster nipple flow? Did you run into any problems when you made the switch? Do have any other tips to share? Let us know in the comments!