If one breast hurts breastfeeding and the other one feels completely fine, that asymmetry is telling you something important.

Pain that is localized to one side is not random. It usually points to a specific issue with how feeding is happening on that side, and in my experience as a Speech-Language Pathologist and Certified Breastfeeding Counselor in Brownsburg, it is almost always something that can be explained and addressed.

Here is what is most often going on when one breast hurts and the other does not.

Why Pain Would Be Different on Each Side

Before we get into the specific causes, it is worth understanding why pain can vary side to side at all.

Your baby feeds differently on each breast. Their positioning is slightly different. Their latch angle is slightly different. If your baby prefers one side, feeds more efficiently on one side, or approaches the two sides with different mechanics, the impact on each breast can be very different.

This is also why solving one-sided pain almost always requires looking at how feeding is happening on that specific side, not just applying a general latch fix.

The Most Common Reasons One Breast Hurts

The Latch Is Shallower on That Side

The most common reason for one-sided breast pain is a latch that is shallower on one side than the other. Even a small difference in latch depth can make a significant difference in comfort.

This often comes down to positioning. If you hold your baby differently on each side, or if there is a difference in how you bring baby to the breast depending on which arm you are leading with, that difference can show up as one side being consistently more painful.

After a feeding, look at your nipple on each side. If one comes out round and one comes out flattened or creased, the creased side has a shallower latch. That is a mechanical fix, and it starts with positioning.

Learn more about what a good latch looks and feels like in What a Newborn Latch Should Feel Like

Baby Has a Preference for One Side

Babies often latch better and more deeply on one side, especially if there is any asymmetry in the body. A baby who prefers to turn their head one way, who has tension in the neck from birth, or who finds one feeding position more comfortable will often have a better latch on one side than the other.

When baby latches better on one side, they tend to be more efficient there too. The painful side is usually the one they are working harder at, with a less stable latch, which creates more friction and compression on the nipple and areola.

Tongue-Tie With Body Tension

A baby with a tongue-tie often has tension in the neck, jaw, and upper body alongside the oral restriction. That tension tends to be asymmetrical, meaning it is usually more pronounced on one side. A baby who is tighter on the left, for example, will often latch shallower and more painfully on the left breast.

This is one of the reasons tongue-tie assessment is not just about looking in the mouth. The whole body is part of the feeding picture.

A Blocked Duct or Beginning of Mastitis

If one breast hurts in a specific spot, feels lumpy or hard in one area, or if the pain is deeper and more aching than nipple-surface pain, a blocked duct may be involved. Blocked ducts can happen when one breast is not being fully drained at feeds, when baby is more efficient on one side, or when a tight bra or bag strap puts pressure on a specific area.

Signs to watch for:

A hard, tender lump in one area of the breast
The skin over the area feels warm or red
Pain that is deep in the breast, not just on the nipple surface
Fever, body aches, or flu-like symptoms (these point toward mastitis, which needs medical attention)

If you suspect a blocked duct, frequent feeding and massage toward the nipple can help. If symptoms include fever or you feel like you have the flu, contact your provider.

Different Nipple Anatomy on Each Side

Sometimes one nipple is flatter, more inverted, or shaped differently than the other. A flat or inverted nipple on one side makes it harder for baby to latch deeply on that side, which can make that breast consistently more uncomfortable.

Learn more about breastfeeding with flat or inverted nipples

Forceful Letdown on One Side Only

Many mamas have a stronger letdown on one side. If baby struggles to manage a fast flow on that side and compensates by clamping or pulling back, it can create a different kind of pain at letdown on one side versus the other.

What to Try First

Focus on positioning on the painful side. Make sure baby is fully facing your body, their chin is pressed deeply into the breast, and they took a wide, open gape before latching. Try a different hold than you normally use on that side and see if it changes anything.

Check the nipple after feeding. A nipple that comes out round means the latch was deep. A nipple that comes out flattened or lipstick-shaped means the latch was shallow on that side.

Try starting on the uncomfortable side first. Babies often latch more deeply when they are hungry. Starting on the side that hurts, when baby is most motivated, can sometimes improve the latch on that side.

Note whether baby turns their head differently on each side. If baby is resistant or stiffer on the painful side, body tension may be involved and chiropractic care alongside feeding support can help.

When to Reach Out

If one breast has been consistently more painful for more than a week or two, if positioning adjustments are not making a difference, or if the pain is significant enough to dread that side, reach out for support.

I work with families in Brownsburg, Avon, Plainfield, Zionsville, and the westside of Indianapolis and come directly to your home.

👉 Book a free postpartum breastfeeding consult

👉 Learn more about in-home breastfeeding support

Frequently Asked Questions

Why does only one breast hurt when breastfeeding?

One-sided breast pain during breastfeeding usually points to a difference in how baby latches or feeds on that specific side. The most common causes are a shallower latch on one side, a baby preference or body tension that makes one side harder to latch on, a tongue-tie with asymmetrical tension, a blocked duct, or different nipple anatomy on each side. Comparing how the nipple looks after feeding on each side is a helpful first clue.

Can a tongue-tie cause pain on only one breast?

Yes. Tongue-tie often comes with asymmetrical tension in the baby’s neck and body, which tends to make latching harder on one side. A baby who is tighter or more restricted on one side will usually latch more shallowly on the corresponding breast, which can cause consistent one-sided nipple pain.

How do I fix a shallow latch on one side?

Focus on positioning adjustments specifically for the painful side. Make sure baby is fully facing your body, wait for a wide gape before latching, lead with the nipple toward the roof of the mouth, and ensure baby’s chin is pressed deeply into the breast. Trying a different hold than you use on the other side can also help, since a new position changes the angle baby approaches the breast from.

When is one-sided breast pain a sign of something more serious?

If the pain is deep in the breast rather than on the nipple surface, if you can feel a hard lump, or if the skin is warm or red, a blocked duct may be involved. If you develop a fever, body aches, or flu-like symptoms alongside breast pain, contact your provider promptly. These can be signs of mastitis, which needs treatment.

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