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Why Is One Breast Bigger Than The Other?

Written by an Expert Aesthetic Content Writer Lisa.
Reviewed by Expert Medical Director Dr. Raj Thethi
Published on: June 23, 2025
Breast Concerns

Why Is One Breast Bigger Than The Other

Why Is One Breast Bigger Than the Other?” Are you dealing with this and are anxious about your body image? This blog is for you!

Breast asymmetry is common and is observed in many people; in most instances, it’s perfectly normal. Breasts are seldom identical twins; they’re more like sisters: similar, but not identical.

Occasionally, the difference is so minimal that no one even notices. However, it may sometimes be quite obvious, particularly when wearing certain attire or viewed from a specific angle. 

Let’s discuss why this occurs and what you can do if it bothers you.

What Causes One Breast to Be Bigger?

Why is my one breast bigger than the other? This section provides all possible causes.
However, your doctor will diagnose the correct causes. The most common causes may include:

1. Genetics

Your genes play a significant role in determining how your body develops and changes over time. So, your breasts are uneven due to inherited characteristics that run in your genes.

2. Puberty and Growth

At puberty, breasts begin to develop, but they don’t always grow at the same rate. One may start growing first, or grow larger than the other. This results in an apparent size variation for some time. In most cases, the smaller breast will eventually catch up; however, for some individuals, the difference persists.

3. Hormonal Changes

Hormones are like messengers in your body, and they’re constantly changing, especially during puberty, period, pregnancy, or menopause. These shifts may make your breasts feel fuller or change shape, and sometimes, one side reacts more than the other. It’s normal and usually resolves once your hormone levels return to normal.

4. Breastfeeding Habits

If you’ve breastfed, you might’ve noticed your baby prefers one side over the other or gets more milk from one breast. Over time, that side can become a bit larger or stretched out. The difference may stay even after discontinuing breastfeeding.

5. Weight Changes

Breasts are partly made of fat, and weight gain or loss can affect each side differently. One may appear fuller or smaller just because of how fat is stored.

6. Posture and Chest Shape

Oftentimes, the way we stand, sit, or move daily can influence how our breasts look. If you always wear a bag on one shoulder or lean to one side when sitting, it can cause the muscles to pull in a different way, resulting in an uneven breast appearance.

7. Medical Conditions

It’s nice to be informed about the medical reasons that may cause one boob to be bigger than the other. 

Moreover, consulting your doctor will be helpful if any of these conditions cause your breast asymmetry.

  • Juvenile Hypertrophy

This rare condition typically appears during puberty, when one breast suddenly grows much faster than the other. It can be upsetting, especially if the size difference is significant.

  • Hypoplastic Breasts

This term is used when one or both breasts don’t develop fully. A hypoplastic breast may be small, narrow, widely spaced, or have a large areola. 

  • Atypical Ductal Hyperplasia (ADH)

This is a condition in which additional cells develop within the milk ducts of the breast. ADH will create lumps or alterations in the shape of the breast, which may cause one side to appear larger than the other.

  • Diabetic Mastopathy

It is a condition in a few individuals with long-standing diabetes on insulin. It creates hard, painless lumps in the breast that can alter their size and shape. 

  • Ectopic Breast Tissue

In this condition, the breast tissue may be found outside its usual area, causing unexpected changes in size or shape.

  • Poland Syndrome 

Poland Syndrome is a rare condition that some people are born with. It can cause one side of the chest to have missing or smaller muscles, which makes one breast look smaller or underdeveloped. 

  • Chest Wall Issues

Chest wall deformities are changes in the shape of the chest bones. Conditions like funnel chest (a sunken chest) or pigeon chest (a chest that sticks out) can cause the breasts to sit unevenly or appear differently sized. 

  • Lumps or Cysts

Non-cancerous lumps or fluid-filled cysts can also change the shape or size of a breast. While many are harmless, they can make one breast look fuller than the other.

8. Injuries or Trauma

Sometimes, one breast might look bigger after a direct hit or injury, like from a fall, a car accident, or a sports impact. The swelling may make your breast seem unequal; however, if the swelling persists or feels unusual after a few weeks, it’s best to consult a doctor.

Cosmetic Treatments to Correct Uneven Breasts 

How can I naturally make one breast smaller than the other? Naturally, you may not be able to correct it. However, if you feel anxious or underconfident due to uneven breasts, here are some safe cosmetic treatments to fix asymmetrical breasts. You may discuss with your practitioner:

1. Fat Transfer

Fat transfer is a gentle and natural way to fix uneven breasts. In this treatment, a doctor removes fat from another part of your body (abdomen, thighs, or hips). The fat is then cleaned and injected into the smaller breast to make it fuller. The results are soft and natural-looking, and because it uses your fat, there’s less risk of rejection. This option works best if the size difference is mild to moderate, and you have enough extra fat for the transfer.

2. Breast Augmentation Surgery

Breast augmentation Surgery is a popular option for uneven breasts. The surgeon may consider putting a breast implant under the smaller breast to match the other one. This procedure helps make both breasts look even and natural. After surgery, you’ll need to rest and avoid heavy lifting for a few weeks. Consulting with a qualified surgeon is essential to discuss your goals, potential risks, and the expected duration of the results.

3. Breast Reduction Surgery

Breast reduction surgery is beneficial if one breast is significantly larger than the other. The surgeon removes extra breast tissue, fat, and skin from the bigger breast to make it match the smaller one. The surgery is done under general anaesthesia, and recovery can take a few weeks. You may need to wear a support bra and follow care steps at home.

How to Cope With It in Daily Life?

Apart from cosmetic treatments, you may cope with breast asymmetry by following these simple tips:

1. Get a Well-Fitting Bra

A well-fitting bra evens out your figure and enhances your comfort. You may give and experiment with a bra featuring removable padding, allowing you to adjust a single side to fit you perfectly. Free fittings can be provided in some lingerie stores, and staff can offer guidance on the ideal style.

2. Try Bra Inserts/Pads

These are firm, moulded pads that lie within your bra cup. They level out the appearance under clothing and are easy to wear. They can be purchased in lingerie stores, pharmacies, or online.

3. Take Charge of Your Mental Well-Being

You may feel upset, embarrassed, or less confident, and that’s completely normal. Everyone has things about their body they wish they could change.

It’s important to know that you’re not alone. Sharing how you feel with someone you trust, such as a close friend, family member, your doctor, or a trained counsellor, can help you feel heard and supported.

4. Love Your Body As It Is

Sometimes, the best way to cope is to accept your body as it is. Many women have uneven breasts, and it doesn’t make them any less beautiful. Self-love and body confidence can grow over time. You deserve to feel good just the way you are.

Which Breast Is Bigger, Right or Left?

It might surprise you to know, but for most women, the left breast is slightly larger than the right. It’s one of those things that’s totally normal but rarely discussed.

According to research, nearly 9 out of 10 women have some level of breast asymmetry. That means the size, shape, or even the position of each breast isn’t the same, and that’s okay.

A study examining 600 women found that the left breast tends to be larger. The difference is often slight, usually less than 20%, and many women don’t even notice it unless they’re looking.

Final Thoughts

One breast larger than the other is something that occurs to so many of us, and in the majority of instances, it’s entirely harmless. Our bodies aren’t designed to be exactly symmetrical, and that’s what makes us special. Remember, asymmetrical breasts are normal, prevalent, and nothing to be embarrassed about

However, if you do ever notice something different, or the change is sudden or concerning, talk to your GP, choose to do something about your bra, opt for surgery, or just embrace your natural shape, that’s your choice.. It’s always best to have it checked, just in case.

If the difference in size is affecting your confidence or making it hard to find clothes that fit just right, you don’t have to settle. Yorkshire Skin Centre offers personalised breast augmentation surgery & Breast Reduction Surgery in Leeds,  designed to restore balance and help you feel more at ease in your own body.

Book A Consultation Now or call us directly at +44 113 519 8608!

FAQs

1. Is it normal to have asymmetrical breasts?

Yes, it’s completely normal. Most people have one breast that is slightly larger than the other.

2. Should I be worried if one breast is bigger than the other?

Not usually. However, if the change is sudden or accompanied by pain, lumps, or skin changes, consult a doctor.

3. What are the five warning signs of breast cancer?

A new lump, change in size or shape, skin dimpling, nipple changes, or unusual discharge.

4. Can stress make your breasts smaller?

Not directly, but stress can affect hormones, which may cause slight changes in breast size.

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About Dr. Raj Thethi - Medical Reviewer

Dr. Raj Thethi

Yorkshire Skin Centre in Leeds is a CQC-registered medical clinic. It is led by Dr Raj Thethi who completed his core surgical training in hospitals around West Yorkshire before branching into aesthetics. Dr Raj Thethi is a Northern Territory Regional Expert for an international dermal filler company called Teoxane. He also sits on their National UK Faculty.

View all posts by Dr. Raj Thethi

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