What to Do If One Breast Produces More Milk Than the Other

You have been breastfeeding your little one for a few months, and have noticed that they seem to stay on one side for longer than the other. While pumping, you may have noticed that one breast seems to produce more ounces than the other. Or maybe you have seen that one of your breasts is much larger than the other. You might even have two completely different breast cup sizes!

If any of this matches your experience, you are far from alone, says Jocelyn Bermudez, IBCLC, a board-certified lactation consultant and one of the hosts of The Snarky Boob Queens. “This is a very common situation,” Bermudez assures. “We sometimes call this the ‘slacker boob phenomenon,’ where one breast is a normal/overproducer and the other has a lower production.”

Many breastfeeding parents are uncomfortable and concerned about feeling “lopsided,” says Bermudez, but this is usually just a cosmetic issue. If your overall milk supply is adequate (i.e., your baby is growing and thriving on your milk), this is usually not something you need to worry about. You can trust your body to make enough milk for your baby, even if one breast does more of the work than the other.

Why One Breast May Produce More Milk 

There are several reasons why one of your breasts may produce more milk than another, says lactation consultant Leigh Anne O’Connor, IBCLC, LCCE. In fact, most breastfeeding parents have some level of breast asymmetry, O’Connor shares.

Like Bermudez, O’Connor assures that regardless of the reason, having one breast that produces more than another is almost never a reason for concern. “If the whole body makes enough milk for the baby, there is no problem,” she says.

Here are some of the reasons why one breast may produce less milk than the other.

Less Mammary Tissue

Your mammary tissue (sometimes referred to as “glandular tissue”) is the tissue in your breast that produces breast milk. When you become pregnant, this tissue increases. It is part of why your breasts are sore at the beginning of pregnancy! The tissue increases even more when your baby is born and your milk “comes in.”

O’Connor says that it is normal for breast anatomy to have variation and for one of your breasts to simply have more mammary tissue than another. This can be a reason why one of your breasts produces more milk than another, and why your baby may prefer one side over another.

Baby Preference

It is very common for your baby to prefer one breast. This preference can happen for any number of reasons, says O’Connor. Your baby may have torticollis, a condition often present at birth, where the neck is turned or twisted to one side. If you have flat or inverted nipples, your baby may prefer to nurse on the less affected nipple.

When your baby tends to prefer one breast, they will nurse there for longer, says Bermudez. “The ‘favored’ size is emptied more frequently, leading to an increased milk supply in one breast over the other,” she explains.

Trauma to the Breast

Trauma to the breast—from incorrect latching, using a pumping flange that is too tight, or experiencing an injury to the breast or nipple—could cause one breast to produce more milk than another. However, Krystyn Parks, MS, RD, a registered dietitian and a certified breastfeeding specialist, says that this is a less common cause of uneven milk supply.

Previous Surgery

Having a previous breast surgery might affect milk supply in one of your breasts, says Bermudez. Surgeries that have the potential to affect your milk supply include any surgery that might have cut the milk ducts or nerves in your breasts, such as breast augmentation surgery or breast reduction surgery. If you are concerned that a previous surgery might be affecting your milk supply, speak to your healthcare provider or a lactation consultant.

Nipple and Breast Anatomy

Just like one breast can have more mammary tissue than another, each of your breasts may have slightly different anatomies, and that can affect how frequently your baby will want to breastfeed from one breast.

For example, says Bermudez, one of your nipples may be larger or smaller than another, and your baby may prefer one size nipple over the other. As O’Connor mentions, having an inverted or flat nipple on one breast could cause your baby to prefer the breast with the more everted nipple.

If you notice that one of your breasts produces more milk than the other while you are pumping, variations in nipple anatomy may be part of the issue, says Parks. “Many women also have different sized nipples, but will use the same size pump parts, so one side may not be fitting correctly causing it to not be as effective,” she explains.

In this case, less milk would be removed, causing that breast to produce less milk overall.

Do You Need to Fix This Problem?

The overall consensus is that if you are producing enough milk for your baby overall, you don’t need to try to fix your uneven supply. Usually, even if one breast is an “underachiever,” says Bermudez, the other breast will make up for it. “Mother's nursing twins or triplets are an excellent example of this,” Bermudez says.

As the Academy of American Pediatrics (AAP) explains, you know that you are making enough milk if your baby is having frequent wet and dirty diapers, they are nursing at least eight times in 24 hours, and they seem satisfied between feedings. Gaining an adequate amount of weight is also a positive sign.

Still, there are some cases where having an uneven milk supply might be a problem worth addressing.

If you are finding that your baby is completely refusing to nurse on one side, Bermudez recommends contacting a lactation consultant to investigate why this is happening. You may also want to consider addressing your uneven milk supply if you are finding that your milk supply is lower, or has gotten lower over time.

If that is the case, you will want to try to figure out what is causing your lowered milk supply, and whether the fact that one of your breasts is producing less milk is contributing to this.

Another scenario that might make you want to address your uneven milk supply, says Parks, is if you are becoming frequently engorged or if your breast engorgement is leading to other issues. “If your baby prefers one side to the point of refusing the other, it can lead to engorgement/mastitis,” Parks explains.

Engorgement can be very uncomfortable, and mastitis is a breast infection that sometimes can cause breast pain and fever, so these are issues to take seriously.

How to Balance Out Your Milk Supply

If you are finding that your uneven milk supply is causing issues such as a decrease in overall milk supply, frequent engorgement or breast infections—or if your “lopsided” look is simply bothering you—there are some things you can do to even out your milk supply.

Breastfeeding is a “supply and demand” system, so the more milk you remove, the more milk your body will make, says Parks. She suggests pumping more on the less productive side to increase your supply.

You can also offer that side first when your baby comes to the breast to feed. “Generally, babies feed more vigorously at first, so they may extract more, cueing your body to make more milk in that side,” says Parks.

In addition to increasing the frequency that you pump or breastfeed from the underproducing side, Bermudez suggests doing breast compressions (gentle squeezing of the breast) when nursing to help your milk flow. You can also try hand expressing or pumping after feedings.

Make sure you have your pumping equipment checked by a lactation consultant, Bermudez recommends. If your breast anatomy is different from one breast to another, you may need a different size flange while pumping to maximize output.

A Word from Verywell

Having one breast that produces more milk than another isn’t usually a serious issue. If you notice that your breast suddenly begins producing less milk than before, if you have an overall drop in your milk supply, or if you begin to have signs of a breast infection in one breast (a tender, red sore spot on your breast, plus flu-like symptoms), you should visit your healthcare provider right away.

Otherwise, you can take comfort in the fact that you aren’t the only one faced with this issue. This is usually a cosmetic issue more than anything. While having a “slacker” breast isn’t always fun, once you are done breastfeeding, your breast size should go back to normal.