Why Does One Breast Produce More Milk Than the Other?

Many breastfeeding mamas notice that one breast produces more milk than the other. Don’t worry: this is completely normal. Learn what causes uneven milk production and what you can do to improve your supply.

Struggling with lopsided breasts? This is one of those things that most moms don’t discover until it happens to them.

My son was just a few weeks old when I discovered that my left breast was slightly larger than my right and was producing more milk. I thought that there may be something wrong.

Perhaps a blocked duct?

After talking to my doctor, I found that many women have one breast that produces more milk than the other and that it’s nothing to be concerned about. However, there are ways you can even out your milk supply.

Start by targeting the cause of the problem. The most common factors that contribute to unequal breast milk supply include:

  • Baby’s preference: It’s normal for a baby to favor one breast over the other. The favorite breast is then forced to produce extra milk to keep up with the demand.
  • Pre-pregnancy size difference: If you had uneven sized breasts before pregnancy, you may continue to have a size difference after pregnancy. The side with less milk likely contains less mammary gland which holds less volume.
  • Mother’s dominant hand: You may find that you hold your baby with your dominant hand more often to maintain comfort. This results in your baby feeding from one breast more often than the other. Less sucking leads to less supply.
  • Inadequate letdown: If you have a forceful letdown, your baby may feel overwhelmed due to the amount of milk produced. In comparison, a weak letdown may require the baby to suck longer and harder to feel full. These issues can cause a baby to favor one breast over the other.
  • Surgery or injury: If you have undergone breast surgery or have suffered an injury to either of your breasts, your milk supply and/or flow may be affected.

What the Experts Say

“Mothers can expect to pump varying amounts of milk on different days and at different times of the day. If her baby breastfeeds some or most of the time, pumping can be adapted to the baby’s breastfeeding schedule. A mother may pump in place of a missed feeding, between feedings, or on one breast while feeding the baby on other breast.”

Counseling the Nursing Mother, Judith Lauwers, Anna Swisher


“Occasionally a baby develops a preference for one breast over the other. Perhaps the favored breast produces more milk or lets it down more rapidly. Sometimes there is no apparent reason – the baby simply prefers one side. One breast can fully support a baby’s nutritional needs. But if a single baby nurses substantially more at one breast than the other, the less used breast may become noticeably smaller. After weaning, the breasts will equal out in size.”

Nursing Mother’s Companion, Kathleen Huggins


“Most babies will prefer one breast to the other. To avoid having the less-desired breast go completely into retirement (and make you look lopsided for the duration of breastfeeding), start each feeding with the breast that is out of favor. Your baby may be less likely to be picky when he’s really hungry.”

The Only Baby Book You’ll Ever Need, Maureen Connors, Marian Borden


“Breast size is not an indicator of milk making capacity. Large breasts may have more fat but little glandular tissue (and therefore low milk output), and small breasts may have mostly glandular and result in high milk output. Each breast has a milk-producing potential that can only be realized by a perfect fit of the baby’s mouth and efficient, timely milk transfer by the baby (or pump).”

Clinician’s Guide to Breastfeeding, Linda Dahl


“Most people find that one breast produces more milk than the other – sometimes as much as twice as much. This is due to an intrinsic difference in breast size and gland number that is not so noticeable when you’re not pregnant. It can also be accentuated by the baby developing a preference for one side over the other.”

DIY Baby!, Shelley S. Binkley


Increasing Milk Supply

If you’re dealing with an uneven milk supply, know that there are ways to boost the supply on your weaker breast. If you or your baby is favoring one breast over the other, pump from the opposite breast between feedings to stimulate milk production.

You need to empty your current supply before your body will make more. You should aim for eight pumping sessions every 24 hours, according to Summit Medical Group.

Many moms find that taking a “nursing staycation” helps give their milk supply a much-needed boost. If you’re unfamiliar with this expression, it’s when you take three days off from work and other responsibilities to spend as much time nursing as possible. During a staycation, moms should get plenty of rest and baby should eat as much as he wants.

Some moms seek the help of milk supply boosters to even out their supply. These boosters are available in prescription form or can be derived from natural sources, such as herbs.

The most common galactagogues include fenugreek, alfalfa, and blessed thistle. Consult your doctor before taking any new medication or herbal supplement.

You may be concerned that one of your breasts is producing more milk than the other, but worry not. This common occurrence is often temporary and may get better once you’ve tried a few different techniques. As you and your baby continue to nurse together, you’ll soon find a solution that makes baby content while evening out your milk supply.


Brandy Dishaw

Brandy is a content specialist and proud mother of two children. She enjoys writing engaging content on parenting, children’s health, and educational topics, and has been published on websites like Modern Mom, Yahoo! Shine, and Livestrong.com. With more than a decade of experience as a writer and mom, she combines research and personal experience to provide her audience with insight to the world of parenting.

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