Baby Bottle Questions You’re Probably Googling
Glass or plastic? How many bottles do you need? What nipple flow should you use? We answer the questions parents ask most.
By
Baby bottles seem pretty straightforward—until you actually have to choose one. Glass or plastic? Wide or narrow nipple? Slow flow or medium? And why are there so many parts?
As a certified lactation counselor (CLC), a parent and someone who covers feeding content at Babylist, bottles are the kinds of things I’ve thought about—a lot. I also spoke to Cindy Herdé, a speech-language pathologist and CLC for her expertise. Between researching and writing about feeding and navigating bottles with my own kids, I’ve seen the same questions come up again and again: Which bottle should you choose? How do you know if the nipple flow is right? What happens if your baby refuses one?
The good news: there’s no single “best” bottle or one right way to bottle feed. A lot comes down to your baby, how you’re feeding and what works for your family. So I’m answering some of the most common bottle questions I’ve come across, from choosing a bottle and nipple flow to bottle refusal, cleaning and more, with additional expert advice along the way.
What's the best bottle for my baby?
As much as we wish we could name one bottle that works for every baby, babies tend to have their own preferences. So instead of focusing on a specific brand, start with the nipple. Look for a slow-flow nipple with a gradual slope that allows baby to get a deep latch, then pay attention to how they feed. If they’re coughing, gulping or leaking milk, struggling to stay latched or seem frustrated throughout the feed, it may be a sign that the nipple shape or flow isn’t a good fit.
From there, think about what matters to you. Do you want glass or silicone instead of plastic? How many parts are you willing to wash after every feed? Will you be switching between breast and bottle? And don’t forget budget—bottles can vary quite a bit in price, especially once you’re buying enough for regular feeds.
Most importantly, don’t stock up until you know what works. Try one or two bottles before committing to a full set. The Babylist Bottle Box is another way to test a few popular options side by side, with plastic and silicone or glass versions to choose from.
Once you have a better idea of what you and your baby prefer, our bottle guides can help you narrow things down:
How many bottles do I need?
How many bottles you’ll need depends mostly on how often you plan to use them. If you’re exclusively bottle feeding, plan on having six to 12 bottles on hand so you’re not washing one after every feed. If you’re only using bottles occasionally or alongside breastfeeding, three to four is probably enough.
Should I choose plastic, glass or silicone bottles?
Plastic, glass and silicone bottles are all safe options, but each has different tradeoffs when it comes to weight, durability, price and cleaning. Plastic is lightweight and typically the most affordable, glass is heavier and a popular choice if you want to avoid plastic and silicone offers a lightweight, durable alternative.
If concerns about plastic are influencing your decision, our Are Plastic Baby Bottles Safe? guide breaks down what the research and experts say.
Here’s how the three materials compare.
What nipple flow should I start with?
Start newborns with a slow-flow nipple. Nipple flow controls how quickly breast milk or formula comes out of the bottle, and you can move to a faster flow when your baby shows signs they’re ready.
The tricky part is that nipple sizing isn’t standardized. Brands may use slow, medium and fast or a numbered system, and one brand’s “slow” isn’t necessarily the same as another’s. “Milk flow rates vary wildly from one nipple to another—from under one milliliter per minute to nearly 38 milliliters per minute—and the flow-rate labels on packaging often don't accurately reflect how fast milk actually comes out,” says speech-language pathologist and CLC Cindy Herdé.
That’s why your baby’s feeding cues matter more than the age or number on the package. If they’re feeding comfortably and managing the flow well, there’s no reason to move up just because they’ve reached the suggested age.
💡 CLC tip: Start slow, then watch your baby—not the package—to decide when it’s time to move up.
How do I know it's time to change nipple flow?
Your baby’s feeding cues will tell you when it’s time to change nipple flow. A feed that’s taking a long time or causing frustration can signal that the flow is too slow, while coughing, gulping or leaking milk can mean it’s too fast. Here’s what to watch for:
“The right nipple is the one that lets a baby feed calmly, at a pace they can manage, without coughing, gulping or milk spilling from the corners of their mouth,” Herdé says. “If a baby struggles with a particular nipple, simply switch—there's no evidence-based universal winner.”
Why is my baby coughing, gagging or leaking milk during bottle feeds?
Coughing, gulping, gagging or milk leaking from the corners of your baby’s mouth can be signs that milk is flowing faster than they can comfortably manage. Try a slower-flow nipple and watch to see if feeding improves.
Position and latch can play a role too. Make sure your baby has a deep, comfortable latch on the nipple and practice the paced bottle feeding technique to give them more control over the flow of milk.
If coughing, gagging or leaking continues despite adjusting the nipple flow, position and latch, you’ll want to bring it up with your baby’s pediatrician or a feeding specialist for help.
Does nipple shape matter?
Yes. Nipple shape can affect how your baby latches and uses their tongue, lips and cheeks while feeding. “A nipple shape that delivers milk with very little effort can encourage a more passive oral-motor pattern—a shallow latch, a tongue that rests low, less active lip and cheek engagement—compared with breastfeeding, which requires a wider, deeper latch and active milk removal,” Herdé explains.
But nipple shape isn’t proven to cause long-term changes in facial growth. Research on orofacial development points more strongly to prolonged pacifier or thumb use than bottle nipple shape.
Do babies need a specific nipple shape if they're breastfeeding?
No. There isn’t one nipple shape that every breastfed baby needs. If you’re switching between breast and bottle, a gradually sloped nipple encourages a wider, deeper latch similar to the latch used while breastfeeding. Paired with paced bottle feeding, this can help make switching between breast and bottle easier. But your baby may feed better from a completely different shape—and that matters more than what the bottle looks like.
“I’d avoid marketing claims that any bottle nipple ‘mimics the breast,’ because none truly do,” Herdé says. “Paced bottle-feeding and a slow-flow nipple are more important than the exact silhouette.”
If you’re not sure where to start, Lansinoh and Pigeon both have gradually sloped nipples and are two options we recommend in our Best Bottles for Breastfed Babies guide.
Do anti-colic bottles actually work?
They can help. Anti-colic bottles are designed to reduce the amount of air babies swallow while feeding, usually through vents built into the nipple or bottle. Some have extra pieces that help manage airflow—Dr. Brown’s bottles are a classic example.
Less swallowed air may mean less gas, but an anti-colic bottle isn’t a guaranteed fix. How your baby latches, their feeding position and nipple flow can also affect how much air they swallow.
How often should I replace bottles and nipples?
For plastic bottles, plan to replace them every three to six months, or sooner if you notice scratches, cracks, discoloration or other signs of wear. Regular use, washing and warming can break down plastic over time. Glass bottles typically last longer and don’t need to be replaced as often, but you should regularly check them for chips and cracks.
Replace bottle nipples about every two to three months, or sooner if you notice yellowing, cloudiness, buildup, cracks or other damage. Nipples are less durable than bottles, so check them regularly for signs that it’s time for a new one.
How long should a bottle feed take—and does my baby need to finish it?
A bottle feed should give your baby time to drink at their own pace and notice when they’re getting full. Rather than focusing on whether they finish a certain number of ounces, watch their feeding cues. Babies don’t always drink the same amount at every feed, and that’s normal.
Bottle-fed babies can be overfed, especially when milk is flowing faster than they can comfortably manage or they’re encouraged to finish a bottle after they’re full. Paced bottle feeding can help by slowing things down and giving your baby more control over the feed.
Most bottle feeds take about 15 to 20 minutes. If feeds are consistently much shorter or longer, take a look at how your baby is feeding rather than watching the clock alone. Coughing, gulping or leaking milk can be signs the nipple flow is too fast, while frustration or difficulty getting milk can mean it’s too slow.
💡 CLC tip: Responsive feeding means watching for signs your baby is hungry or full rather than focusing on getting them to finish every last ounce.
What is paced bottle feeding?
Paced bottle feeding is a technique that slows down a bottle feed and gives your baby more control over the pace. Instead of holding the bottle tilted down, hold it more parallel to the floor. Tilt it just enough to keep milk in the nipple while your baby drinks, then lower the bottle and pause every few sucks before offering it again. This creates a feed-and-pause rhythm that’s more similar to feeding at the breast.
But paced feeding isn’t just for babies who switch between breast and bottle. It can be helpful for any bottle-fed baby by giving them time to recognize fullness cues and take breaks throughout the feed.
What if my baby refuses the bottle?
Bottle refusal can be frustrating, especially when what seemed to be working suddenly doesn’t. And babies have strong opinions, no matter how new they are to the world.
If your baby usually breastfeeds and you’re introducing a bottle, start with a slow-flow nipple and the paced bottle feeding technique. It can also help to have another caregiver offer the bottle, since some babies are more willing to try it with someone other than the nursing parent.
If your baby previously took a bottle and suddenly refuses it, look at what else may have changed. Nipple flow, feeding position and even your baby’s developmental stage can all affect how they feed. You can also experiment with the temperature of the milk or try a different bottle or nipple shape.
If bottle refusal continues or your baby is having trouble getting enough milk, check in with their pediatrician or a feeding specialist.
💡 CLC tip: If a bottle suddenly stops working, don’t assume you need a new one. Start with nipple flow, feeding position and what else may have changed around the time the refusal started.
Do I need to warm my baby’s bottle?
No. Breast milk and properly prepared formula don’t need to be warmed before a feed. Some babies prefer warm milk, while others are happy drinking it cold or at room temperature.
If your baby prefers a warm bottle, use a bottle warmer or place the bottle in a bowl of warm water for a few minutes. Don’t use the microwave—it can heat milk unevenly and create hot spots that can burn your baby’s mouth.
When preparing powdered formula, follow the instructions on the formula container and any guidance from your baby’s healthcare provider. The water temperature used to safely prepare formula is separate from the temperature at which you serve it.
Can I save a bottle my baby didn’t finish?
You may see different recommendations for leftover breast milk depending on where you look. The CDC takes a more conservative approach, recommending that leftover milk be used within two hours after a feed. La Leche League International gives a similar one-to-two-hour guideline but points to research suggesting leftover milk may be safe for longer, though more research is needed. The Academy of Breastfeeding Medicine also recommends using leftover milk within one to two hours while noting there isn’t enough research to establish a definitive cutoff. How long milk remains safe can depend on factors like room temperature and how much bacteria was introduced during the feed.
Formula has different guidelines. Once your baby starts drinking from a bottle of formula, the CDC recommends using it within one hour and tossing anything that’s left after that. Prepared formula that hasn’t been offered can stay at room temperature for up to two hours, or you can refrigerate it right away and use it within 24 hours.
Do I need to sterilize my baby's bottles?
Not necessarily. For most healthy, older babies, thoroughly cleaning bottles after every feed is enough. The CDC recommends sanitizing bottles and feeding parts at least once a day for babies under two months old, babies born prematurely or babies with a weakened immune system.
You also don’t need a dedicated sterilizer to sanitize bottles. You can boil them, use your dishwasher’s sanitizing cycle if the bottles are dishwasher safe or use a countertop sterilizer. A bottle washer that washes, sterilizes and dries can be convenient if you want one machine that does it all, but it’s not a necessity.
Whatever method you use, follow your bottle brand’s cleaning instructions since materials and dishwasher recommendations can vary.
Expert Sources
Babylist uses high-quality subject matter experts to provide accurate and reliable information to our users. Sources for this story include:
Cindy Herdé, SLPD, CCC-SLP, CLC, a speech-language pathologist, certified lactation counselor, and founder of Talk Eat Play.
