What It Means When Your Left Breast Is Bigger Than Your Right

I've heard people say that it's a common thing for a woman's left breast to be bigger than her right, but I wasn't sure if it was true or what the science was behind it. However, when I'd ask my friends about it, they mostly agreed that it was also true for them. So why is this the case and what does it mean, if anything, if one person has it versus another? Here's the inside scoop.

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"There have been multiple theories proposed for breast size and the difference in sizes when comparing left to right, but it may be associated to possible hormonal changes, like during ovulation," says Dr. Jessica A. Shepherd, director of Minimally Invasive Gynecology at the University of Illinois at Chicago and SweetSpot Labs expert. "Breast asymmetry is typically seen in puberty where there are rapid growth spurts and it is possible that one breast responds more to surging estrogen levels than the other. But when speaking particularly about the left, there is no general consensus." 

There have, however, been studies done on breast size, but most of them, according to Dr. Shepherd, have focused on the risk that was increased among women with the largest breast area and their chances of having breast cancer. Others have looked at breast size differences and how they relate to their geographical and ethnic origin. "The reports are varied, however, one study in particular was done with 100 women who desired breast augmentation, and of those women, 88 percent had natural asymmetries. Also seen in a study published in the Annals of Plastic Surgery, 600 women were evaluated, and it was found that the left breast was larger." 

Grand Rapids, MI, plastic surgeon Bradley Bengtson, MD, says that although he hasn't seen this size difference in his breast augmentation patients specifically, it's very well-known that the breasts are not symmetrical. "One of my favorite professors used to tell me, 'Breasts are sisters, not twins,' and I tell my patients, too."

So, if your left breast is larger than your right, no need to fret. It appears to be one of those unexplainable anatomical mysteries that affects many women of all different shapes and sizes for no good reason. And, if your asymmetry is significant, there are several ways it can be corrected. "For mild asymmetry, we use fat transfer because we can shape the smaller breast and add small increments of volume where we want it," says Dr. Bengtson.

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If the symmetry is more significant, a breast implant can be used to even things out. "Implants are usually 30–40 cc different in volume for the next implant size up or down so we can definitely dial in and make breasts more symmetrical. In addition, we have four different projections of implants, so in patients with rib and chest wall deformities (which is extremely common), we can alter projection of the implant and thus the breast as well," explains Dr. Bengtson.

Because breast asymmetries are so common, it's important to be aware of what is a "normal change" in your breast size and what isn't. Recognizing signs of breast cancer, which will affect one in nine women in their lifetime, is crucial for women. "Be sure to talk to your doctor if you have changes in how your breasts look or feel, such as a lump or firm feeling that is near your breast or under your arm," says Dr. Shepherd. "Also check for nipple discharge or changes that do not look like milk and are possibly bloody. Another sign could be skin on your breasts that is itchy, red, scaling, dimpled or puckered."

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  • Bla bla
    Posted on

    Yes I too think that due to the presence of heart in the left side... The left boob is bigger then the right one

  • Pamela Chambers
    Posted on

    I am 54 yrs. old and my left breast is dramatically larger than the right. This only started within the last year or so. Is there a medical reason?

  • Sarah
    Posted on

    What are some ideas to balance things out if you can’t afford or don’t want to have it done surgically. I have found as I’ve gotten older, in my mid 40’s now, that the difference is noticeable to others. I am ver self conscious about it and tend to stand tilted so it doesn’t look as noticeable. Anyone have ideas?

  • Aqsa Riaz
    Posted on

    can you tell what is the reason behind if your right sided breast is bigger than left?

  • Anonymous
    Posted on

    Having weight issues myself, thr left side breast is bigger as is my stomach, and arm. Im right handed. Years ago everything seemed even. So im pretty sure useing my right hand and arm for many years has kept my right side toned better than the left. Look at some women athletes...they work out so much lifting weights or what have you that some of them end up with no breasts.

  • SD
    Posted on

    I absolutely agree with Mary. If you’re right-handed your right breast will be smaller due to conditioning of the surrounding muscles. I can’t believe the article treats this like a big mystery. On a related note, if this is a fairly well known fact, why do designers continue to design wrap tops so that the breast under which the wrap goes is the left one? I’ve noticed that this makes my left breast look even larger so I avoid these tops at all cost. Seems like a silly error in judgment on the part of designers. (They also seem to put pockets on the left breast as well. What are they thinking?)

  • Jan
    Posted on

    Very hard to by a decent fitting bra with mine - they are very different to each other.

  • Mary
    Posted on

    If you are right handed your right breast is going to be smaller. For common sense reasons I have always thought it was because your primary appendage will be used most, worked out more doing common every day things, as well as the muscles around it - a.k.a your pecs/breast.

  • Anonymous
    Posted on

    Since because of Heart in the left side which is constantly activated the left breast and so bigger.