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

You've 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,” assures Bermudez. “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 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), it's 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, shares O’Connor.

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's 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's normal for breast anatomy to have variation and for one of your breasts to 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's 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're concerned that a previous surgery might be affecting your milk supply, speak to your health care 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. 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.

Do You Need to Fix This Problem?

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

As the Academy of American Pediatrics (AAP) explains, you know that you're making enough milk if your baby is having frequent wet and dirty diapers, they're 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're 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're finding that your milk supply is lower, or has gotten lower over time.

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're finding that your uneven milk supply is causing issues such as a decrease in overall milk production, 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 breast 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.