There are many possible causes for feeling a heaviness in your breasts, including changes in hormones caused by menstrual cycles, pregnancy, or breastfeeding, or certain medications. Discuss any concerns with a doctor.

It’s natural to feel concerned when you notice changes in your breasts. But rest assured, breast changes are a normal part of female anatomy.

If your breasts are feeling heavier than usual, it’s probably not anything to worry about. Keep in mind that breast heaviness is rarely a sign of cancer.

Here’s the lowdown on some of the more common culprits behind breast heaviness.

Fibrocystic breast changes are very common. According to the Mayo Clinic, half of women experience them at some point in their lives. This noncancerous condition can cause a variety of changes in the breasts, including the accumulation of water in the breast tissue. When your breasts swell and fill with fluid, they’ll feel heavier than usual.

These changes can happen in one or both breasts. They might occur every month at a certain point in your cycle or follow no discernable pattern. In some cases, you might have constant symptoms.

Other common symptoms of fibrocystic breast changes include:

  • free-moving lumps
  • pain or tenderness that’s often worse right before your period
  • pain that extends into your armpit or down your arm
  • the appearance or disappearance of lumps or lumps that change size
  • green or brown nipple discharge

As cysts appear and disappear in your breasts, they can cause a scarring and thickening of the breast tissue, called fibrosis (fibrosis). You can’t see these changes, but they can make your breasts feel lumpy or heavier than they used to.

Breast pain and swelling often follow a monthly pattern that’s clearly connected to your menstrual cycle. This is known as cyclical breast pain.

In the days leading up to your period, your estrogen and progesterone levels can fluctuate dramatically. Estrogen and progesterone increase the size and number of ducts and glands in the breast. They also cause your breasts to retain water, making them heavy and tender.

These types of cyclical breast changes usually affect both breasts. Symptoms may get progressively worse in the two weeks leading up to your period, and then disappear.

You may notice:

  • swelling and heaviness
  • a heavy, dull, and aching pain
  • lumpy breast tissue
  • pain that radiates to the armpit or outside the breast

Breast swelling is sometimes one of the first signs of pregnancy. Your breasts can begin to swell about one to two weeks after conception.

Swelling occurs because of the hormonal changes happening in your body. They can cause the breasts to feel heavy, achy, and tender. Your breasts might also appear larger than usual.

If you have breast swelling and heaviness accompanied by a late period, then you may want to consider taking a pregnancy test.

Other early symptoms of pregnancy include:

  • missing one or more periods
  • light spotting
  • nausea or vomiting
  • fatigue

If you’re pregnant, your breasts will continue to grow up to, and even past, your due date. In the final stretch of your pregnancy, they may become even heavier as your body prepares for breastfeeding. Learn more about breast changes during pregnancy.

If you’re breastfeeding, then you’re probably getting used to the feeling of full, heavy breasts and painful nipples. Breastfeeding is challenging, but it can be particularly difficult when you experience an oversupply of milk.

The feeling of fullness and heaviness can sometimes progress into a condition called engorgement. Engorgement happens when too much milk builds up in your breast. It can be very painful.

Other symptoms of engorgement include:

  • breast hardness
  • tenderness
  • warmth
  • throbbing pain
  • redness
  • flattened nipple
  • low-grade fever

Engorgement is common during the first week of breastfeeding, but it can happen at any time. It’s more likely to occur when you aren’t feeding your baby or pumping often enough.

Certain medications can cause breast-related side effects. The most common sources are hormonal medications such as birth control pills, fertility treatments, and hormone replacement therapy.

Hormonal medications work in different ways to regulate your hormone levels. Fluctuations in your levels of either estrogen or progesterone can cause fluid retention in your breasts, making them feel heavy.

Certain antidepressants have also been connected with breast symptoms, namely pain. These include selective serotonin reuptake inhibitors (SSRIs), such as sertraline (Zoloft) and citalopram (Celexa).

Breast infections, known as mastitis, are most common among those who are breastfeeding. Mastitis can cause inflammation, leading to swelling and feelings of heaviness in the affected breast.

It tends to happen when milk becomes stuck in the breast, allowing bacteria to grow out of control. This can happen because of a blocked milk duct or when bacteria from your skin or your baby’s mouth enter your breast through your nipple.

Symptoms of mastitis include:

  • tenderness
  • breasts that are warm to the touch
  • swelling
  • pain or burning (can be constant or only while breastfeeding)
  • a lump in the breast or thickening of breast tissue
  • redness
  • sick, rundown feeling
  • fever

Heaviness usually isn’t a breast cancer symptom. The exception to this is inflammatory breast cancer. Still, it’s the least likely cause breast heaviness.

Inflammatory breast cancer is very rare, making up only about 1 to 5 percent of all breast cancers, according to the National Cancer Institute. It’s an aggressive cancer that often comes on quickly. As a result, you’ll likely experience some other symptoms as well.

This type of breast cancer causes redness and swelling of the breast tissue. Sometimes the breast can increase dramatically in size and weight in a matter of weeks.

Other symptoms of inflammatory breast cancer include:

  • swelling and redness covering a third or more of the breast
  • breast skin that looks bruised, purplish, or pink
  • breast skin that resembles an orange peel
  • burning or tenderness
  • nipple turning inward
  • swollen lymph nodes

It’s perfectly normal for your breasts to feel heavy from time to time, but it never hurts to get things checked out. If you’re worried it could be something serious, speaking with a doctor will definitely help. If you don’t already have a primary care provider, you can browse doctors in your area through the Healthline FindCare tool.

Keeping track of how your breasts feel throughout the month may also provide some peace of mind if you find that the heaviness seems to occur the week or so before your period. If that’s the case, an over-the-counter pain reliever, like ibuprofen (Advil), should offer some relief.

But in some cases, it’s definitely best to make an appointment as soon as possible. Infections, for example, can only be treated with prescription antibiotics.

If you’re in pain, either constantly or intermittently, your doctor can help figure out the cause of your pain, whether its your menstrual cycle or something else. They can recommend medications that will help regulate your hormones or dosage adjustments that may work better than your current treatments.

If you’re taking an SSRI, your doctor may recommend switching to a different antidepressant with fewer side effects or adjusting your dosage.

If you’re having trouble breastfeeding, your best bet is to speak with a lactation consultant. They can advise you on how often to feed or pump each breast and how to be sure your breast empties. You can ask your doctor for a referral or search the International Association of Lactation Consultant Association’s directory.

Any new lump that doesn’t resolve on its own within a few weeks should be checked out by a doctor. It can be hard to tell the difference between a benign cyst and a cancerous tumor.

Fibrocystic breast changes can be alarming, and it isn’t possible for you to tell the difference between a cyst from a tumor. While cysts tend to be softer, more painful, and easier to move, that’s not always the case. Only a doctor can tell you for sure.

Warning signs

Keep in mind that breast heaviness alone is very rarely a sign of a serious problem.

But if you notice the following symptoms, it’s best to see a doctor as soon as possible:

  • a hard, pain-free lump
  • redness or discoloration of your breast
  • pain or burning while breastfeeding
  • a fever
  • a flattening or inversion of the nipple
  • blood leaking from your nipples
  • severe fatigue or rundown feeling

As well, see a doctor if your family has a history of breast cancer or you’ve had breast surgery in the past.