So, you’ve decided to start using a breast pump. You’ve read the instructions and you’ve grabbed a glass of water to sit down and start expressing and then you remember hearing you friends talking about something to do with sizing your nipples! Was that right?

Yes! You heard it right. Making sure you have the perfect fit when you are using a breast pump is really important to make sure you get the best flow of milk and cause no pain.

None of us have exactly the same size nipples, just like we all wear a different shoe size, breast shields are the same. You may have different sizes between your left and your right nipple too, this is perfectly normal. Medela offer five breast shield sizes to make sure you get the best fit for you.

Now I’m going to take you through our new sizing guide and leave you with the links to watch our super simple video and our infographic on breast shield sizing.

Let’s Look at the Anatomy of the Areola and Nipple

Tips for Using a Breast Pump

What’s important here is that you can see the difference between the nipple and areola. When you measure the nipple it’s important to measure in the right place.

Why Might I Need to Try a New Size Breast Shield?

Here are a few questions that you can start with:

Does your nipple rub the tunnel sides to the point of causing discomfort?

Do you see excessive areola being pulled into the tunnel?

Do you see any redness?

Is your nipple or areola turning white?

Do you feel unexpressed milk after breast milk pumping?

If you answered yes to any of these questions is it a good idea to measure your nipple and find out what breast shield size would be a better fit.

How Do I Measure My Nipples?

Step 1: Use a ruler or tape measure to measure the diameter of your nipple base in millimetres (mm). As per the picture diagram.

Step 2: Based on your nipple measurement, determine your breast shield size, from the diagram.

If your nipple measures 25mm, then the recommended breast shield size is 30mm.

If your nipple measures 21mm, then the recommended breast shield size is 27mm.

Tips for Using a Breast Pump

We recommend a larger breast shield diameter than your actual nipple base size because when a breast pump is used it creates vacuum making your nipple larger. Having a gap of about 4mm between your nipple and the breast shield allows for your nipple to expand comfortably once you are pumping. This ensures your milk keeps flowing and no pain is caused to your nipples.

How Can I Test My Breast Shield?

The next thing you can do is test what happens to your nipple with the original 24mm breast shield which came with your pump.

First, centre your nipple and gently hold the 24mm breast shield against your breast.

Next, adjust the pump to your Maximum Comfort Vacuum to achieve optimum suction level. (Turn the suction level up until it just starts to feel a little uncomfortable or “pinchy.” Then turn the suction level back down one or maybe two, where it now feels comfortable. This ensures you are using the suction level at the highest, but most comfortable level for you, and this will express the most milk out)

Watch your nipple once the pump has moved on from the initial fast stimulation phase to the slower expression phase. What do you see? Use the diagram below to work out if the breast shield is too small or too large.

Tips for Using a Breast Pump

Hopefully this guide helps you make sure your nipples are comfortable when you are expressing. Please find our full A4 guide which you can download and our short video clip here.


If you are still unsure that you selected the correct size, we advise that you see a lactation consultant or breastfeeding specialist to help you further.

What breastfeeding tips would you like to share with the other mums in our community? How would you describe your own breastfeeding experience? Please join the conversation here or on our Medela Australia Facebook page.

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