Ask the LC: PersonalFit Breast Shield Sizing

June 30, 2015

Breastfeeding is one of the most magical and rewarding experiences in a mom’s life. But without proper guidance and equipment, it can also be stressful, frustrating and even painful. Thankfully, expert advice combined with the right PersonalFit Breast Shield size can help make your pumping experience is as positive as possible. We recently asked our Facebook community what questions they had about proper shield size, and then our Clinical Education Specialist, Irene Zoppi, offered her best advice. In case you missed it, here’s an overview of some of the most common questions from the chat and Irene’s answers:

Is there a standard measuring system I can use in order to get the right shield size before baby arrives? – Shiree M.

Our breast shield sizing guide can help. However, please note that measuring is only part of the fitting process. You will also have to use your pump to see what changes occur to your body and you don’t want to initiate pumping while pregnant.

I’m currently using the 27 mm breast shield size. During pumping, each nipple pulls diagonally outward so that they always end up rubbing against the side. I have to continually reposition the shields during pumping. Would changing sizes be beneficial – or any other tips to help? Baby is 8 months so have about 4 more months to go, hopefully. – Katie E.

Changing sizes may be very beneficial especially if pumping is painful. Congratulations on breastfeeding for 8 months, that is a wonderful thing!

I am preparing to welcome my second child. I am quite larger than I was with my first child bust wise. I was using a 27 mm shield but I am not sure if that will work this time. I tried to measure my new size and it didn’t come out right. What should I do? – Sarah S.

The size of your breasts probably won’t affect pumping or measuring your nipples. Try using the size you currently have; and a new pump kit will come with 24 mm shields – you can do your own comparison – but wait until after the baby is born. The measuring guide is only the first step – you have to wait to see what happens to your nipples when you pump.

I’m using standard size (24 mm) flanges and my right nipple is fine, but my left is getting blisters and cracking all the time. Could I need different sizes? – Kelsey G.

Yes – some moms do need a different size breast shield for each breast. That’s completely normal. To learn more about proper fit, you can visit our breast shield sizing guide.

I use the 24 mm shields and notice white rings around the base of my nipples. Is this normal? Also, my nipples swell and get some purple spots on them too. Is that normal? – Laramie H.

It sounds like the breast shields may be too small. I suggest trying a larger size to see how your body responds. You may even need two different sizes during the day – one size when your breasts are very full, and another size when you are not as full. You can even be a different size per side.

I have been using 27 mm now for almost 12 weeks and I have a raw, red, chaffed ring around my nipple that also looks stretched out. If I use the 24 mm, which seem to fit better in the beginning, my nipples tend to swell towards the end and I do not yield as much milk as the 27 mm (usually .5-1 oz less). I am exclusively pumping. Any input? – Amanda O.

Breast shield sizing can change over the course of lactation. You may wish to try one size when you are most full – then the other when your breasts are not as full. Perhaps this will make a difference, as the chafing is not a good sign. You may also want to try using a purified lanolin while pumping.

Often times, when I pump and sometimes while nursing, I will get severe burning. Does that mean I need bigger shields? – Tanya H.

Burning may represent a different issue, especially if you experience this while also nursing. You can try a larger breast shield size, but I’m thinking you should have this checked out by a lactation professional.

Where do you go to get measured? – Jasma H.

A Lactation Professional can help you measure your nipples and determine which size might work best. You can also follow the measurement instructions in our blog. To find lactation support near you, you can also search here.

I’m using a 27 mm and that seems to be comfortable, yet I’ve noticed my nipples now have an indentation that resembles the breast shield even hours after I’m done pumping. Is this normal? I’ve been pumping for about two months, three times a day. – Priscilla S.

This may be okay – but you may wish to try a different size to see if that makes a difference. Also know that sizes do change over the course of lactation. What was a good fit previously may have changed. Does this happen on both nipples or just one? If it’s just one, you could need a different size for each breast. Or, you may also need one size when very full and another size when your breasts are more drained.

This is the third baby I’ve exclusively pumped with. I’ve met with lactation consultants and struggled with latching. I have very flat nipples and pumping isn’t comfortable for me. Baby is only 7 weeks and I feel like I have a long way to go. I’ve changed sizes based off the new measurements. It’s more comfortable for sure, but still sore. Any other suggestions to help heal my cracked, sore nipples? – Sarah Y.

So sorry to hear this. You have done such an awesome job getting through this. You may want to try using some purified lanolin on your nipples while pumping. You may find this helpful. Hang in there!

I have been using the 24 mm shields, and I have noticed that my nipple rubs on insides of the shield. The issue is that they only do this during about 1/4 to 1/3 of my pumping sessions (I pump 3x/day at work). On these days, it results in poor output. I ordered the 27 mm shields from Medela, but most of the time, they are too big, and I also have poor output. One day, they work great, and the next day, they hurt and are clearly too big. And I know that my breasts are not empty on these days because they feel full when I am done. I spoke with a Medela consultant to check out pump issues, and she said everything with my pump is fine. I don’t have time to keep switching breast shields at work because I only get 15 minutes to pump, and I need every minute of that time. Is it normal for my nipples to be more full sometimes? Or is there another issue? – Michelle Z.

Believe it or not, you may be in-between sizes. You may notice you need one size when you are more full and another size when less full. You may even be two different sizes – one breast needs one size, the other breast needs a different size. Try using breast massage while pumping, too. Many mothers find this quite helpful when pumping.

My baby is 5 weeks have I have recently supplemented because she wasn’t gaining weight. I am going back to work in 2 weeks and only have enough freezer milk for a day. When I pump I only get 1-2 oz. from both breasts. I have tried every size flange and nothing seems to drain me, so I’m assuming it’s not that it’s just that I don’t respond to the pump. What do I do to get more milk? Do I pump after feeding or during? Could my lack of water or drinking coffee be the problem? My baby feeds almost every hour due to falling asleep so quickly. I hope I didn’t screw something up by having to give her formula a few times a day. I don’t want to be a failure. – Christina H.

Moms don’t fail at breastfeeding. You need lots of support! Making milk is from draining breasts, so the more you drain your breasts – the more milk you’ll make. Drink water to quench your thirst, but you don’t have to drink gallons…a cup of coffee a day won’t be an issue. My suggestion is to contact someone (either lay or professional) in your community for the breastfeeding support and counseling you deserve. Don’t give up! Get some help from others.

I have the smallest size shield but it is still double the width of my nipples. It isn’t painful to pump but I’ve read so many times how important it is to have the right fit. What should I do? – Holly S.

You may want to try searching online for alternatives for smaller shield sizes. But also, consulting with a lactation professional who can visualize what is happening when you pump can be very helpful.

According to the size chart, I am using the correct size flange (24 mm). However I am not completely emptying my breast when pumping. Why is that? I have a pump in style advanced. – Amanda Z.

I suggest you try breast massage while pumping and go ahead and try the next size larger (27 mm) to see if there is a difference.

How important is a proper size breast shield? My first pump had a “one size fits all” breast shield. Not until I got my hospital grade pump from my insurance did I even learn about sizing. – Emily M.

While other brands may have “one size fits all” breast shields, Medela offers 5 different shield sizes. Breast shield fit is important for pumping success because a poorly fitted breast shield can critically affect your milk supply. If your shields are too small they can constrict the superficial milk ducts and down regulate milk supply. If they’re too big, this can prevent your pump from draining the breast effectively, resulting in decreasing milk supply as well. If you have other questions about breast shield fit, our guide is a good place to start.

What are the disadvantages of using the wrong size? I’m pretty sure mine are too large but I’ve invested so much into shields that I can’t afford to buy new sets. And I can’t find them in stores. – Nikki M.

You can search online for breast shields or search at a hospital. The real issue is that your milk supply can be critically affected; too small, will constrict the superficial milk ducts and down regulate milk supply; too big, won’t drain the breast effectively resulting in decreasing milk supply as well.

I used the Medela nipple diameter chart and my flange size would be 21, however, when I use the 24 mm, my nipples rub a bit against the shaft and there’s a red ring around my breasts so they may be too small. Which one do I go by? – Kennedy S.

The guide is a starting point for fitting. Your breasts/nipples may change with pumping. If you see a red ring at base and some rubbing of your nipple, the breast shield is too small. I suggest going larger than the 24 mm. Fitting is about using the measurement as a guide and then seeing what actually happens with the elasticity of your nipple.

I’ve been using the 30 mm shield but it seems like it may be too big. And the 27 mm seems too small. Should I continue to use the 30? – Chandra B.

Does this happen on both nipples? You might need a different size per side. Also, you can try switching the shields – so use the 30 mm one time, the 27 the next.

No matter what size shield I use, it always pulls my areola in. I was told in the hospital that I have flat nipples. Is this just something that happens? It’s not painful, just wondering if I’m doing something wrong? – Sarah O.

Don’t worry. This would be a problem if it hurts to pump or you see skin redness or irritation. It may be normal for you, and the elasticity of your nipple.

Is it true that the nipple is not supposed to touch at all? And a slight amount of the areola is supposed to move? – Heather H.

The criteria you mentioned is in a perfect case scenario. The nipple should not be touching the sides of the tunnel – some areola tissue entering into the tunnel is okay as well.

How do you find the proper fit if you nipples are flat or inverted? – Michelle H.

I suggest starting with the size 24 mm breast shields that come with the pump. Start pumping and see what occurs with your nipple(s). If pumping is uncomfortable, try a larger size.

Do you have more questions about selecting the right size breast shield? Check out our new breast shield fit guide for tips that can help ensure you’re pumping comfortably and efficiently. You can also reach out to Irene or one of our on-staff Lactation Professionals on our website for one-on-one guidance via email, completely free of charge. Keep up the good work, mamas! You’re doing a great job!


Irene Zoppi, RN, MSN, IBCLC, joined Medela in 1999 as a clinician for the Breastfeeding Division. She currently serves as a Clinical Education Specialist focusing on advocacy outreach. In this role, Irene acts as a vital resource for groups assisting breastfeeding mothers and infants. She has been frequently interviewed on radio and online regarding breastfeeding issues for mothers and clinicians.

59 thoughts on “Ask the LC: PersonalFit Breast Shield Sizing

  1. Hello,

    I’ve been pumping for two months now with the standard size breast shields. I haven’t had any discomfort, however I’ve noticed a thumping sound while I’m pumping (my nipples also rub to the right/left of the shield) I believe the shield is sucking to much of my nipple in, is that correct? Do I need to go bigger or smaller for the breast shield? I’m confused.

  2. I am currently using a 21mm breast shield and the milk leaks out the flange while I pump. I see a large part of areola being pulled into the shield. Since 21mm is the smallest available size, what should I do?

  3. I’ve tried the normal 24mm shields and a size smaller with no luck. Whenever I pump the tip of my nipple is crushed against the end of the shield area so I have to wedge my fingers in the opening of the shield to hold my breast out further so that it’s not constantly crushed. Would a larger size help or should I just keep doing this?

  4. Jamie L Govern says:

    I’ve been breastfeeding for 7 months now and all of the sudden my nipple is sucked so far into flange it touches the tunnel. I’ve tried different sizes, vacuum levels, everything. Doesn’t hurt, but after pumping I have a flattened nipple and it’s a little purple. Idea’s??

    • Hi, Jamie. We recommend you reach out to a Lactation Consultant with your question so they can give you personalized feedback. You can contact our International Board Certified Lactation Consultant directly through, or through a 24/7 LC subscription on your MyMedela app.

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