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You’re weeks away from your period. You’re pretty sure you’re not pregnant. And yet, something in your midsection hurts. It’s sharp, like period cramps, only the pain is different… and just on one side. What. Is. Happening?

If you’re about midway through your cycle and suddenly experience weird cramps, you’re likely ovulating.

Ovulation pain happens to about 20 percent of people who ovulate, so if your fertile window feels less than pleasant, you’re not alone. In fact, ovulation pain is so common that the Germans came up with a word for it: mittelschmerz. (This cleverly translates to “middle pain,” btw.)

Most of the time, ovulation pain is fleeting and harmless. (Whew.) But there are a few things you should know about it — and about pelvic pain in general.

First up, let’s review what happens during ovulation, to understand why it can be painful.

At birth, your ovaries contain every single egg cell you’ll ever have. Then, each month during your menstruating years, your body’s hormones shift to increase your levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), as your ovaries prepare to release a mature egg around the middle of your cycle.

That timeline looks like this:

Days 6 to 14: FSH starts to rise, causing a follicle in one of your ovaries to start maturing.

Days 10 to 14: That follicle grows into a fully mature egg.

Around day 14: LH surges, triggering the release of the egg down your fallopian tube to your uterus.

As a follicle matures, it stretches and grows, which can cause pain and discomfort — and even spotting or light bleeding. When the egg is released and the follicle that held it ruptures, you can sometimes feel it.

So why is ovulation sometimes a real pain in the… ovary? There isn’t one single answer. The follicle’s growth may cause the pain, but your egg also has to exit through the ovary wall (there’s no secret door or easy way out) to start its trip down the fallopian tube to your uterus. Either one may be what you feel.

How do you know it’s ovulation pain? Symptoms include:

  • it’s been a couple of weeks since your period
  • felt on only one side
  • lasts for a few minutes to a few hours, or up to 24 or 48 hours
  • sharp, like a cramp (but different — IYKYK…)
  • happens about halfway through your menstrual cycle
  • noticeable but rarely severe
  • may switch sides each month
  • light spotting (sometimes)
  • mild nausea (sometimes)
  • accompanied by other signs of ovulation, like “egg white” cervical fluid, change in the position of your cervix or a slightly lower (then higher) basal body temperature

Aside from run-of-the-mill mittelschmerz, midcycle pelvic pain and bleeding can have other, more serious causes. They include:

Cysts

Ovarian cysts are fluid-filled sacs that develop on or in an ovary. Usually, these small, common cysts form during ovulation, then go away after an egg is released. You might even have one and never know it existed!

Sometimes, cysts keep growing, which can cause bloating, pressure, swelling and pain on one side of your pelvis. When they rupture, cysts can cause sudden, severe pain. Most cysts are not cancerous, but your doctor can diagnose them.

Cysts also cause symptoms like:

  • pain while pooping
  • fullness and/or pressure in your abdomen and/or bladder
  • nausea and/or vomiting
  • sore or tender breasts

Polycystic ovary syndrome, which affects 1 in 10 people with ovaries, also causes cysts to develop. Your doctor can use imaging like ultrasound or a CT scan to diagnose PCOS and its associated cysts.

Endometriosis

With endometriosis, tissue similar to your uterine lining grows elsewhere in your pelvis and beyond, which can lead to pain that resembles ovulation pain. However, endo pain is usually more severe than ovulation pain, and it can happen during your period or any time during your cycle.

Endo symptoms include:

  • painful periods
  • painful bowel movements
  • heavy bleeding during your period and at other times in your cycle
  • diarrhea or constipation
  • nausea

Endo can lead to scar tissue and adhesions, and that tissue can become more irritated and painful as your hormones fluctuate throughout your cycle.

Surgery is the only way to confirm that you have endometriosis, but your doctor can help you manage suspected endo pain based on a pelvic exam, imaging tests, your symptoms, and medical history.

Pelvic inflammatory disease

Pelvic inflammatory disease is an infection that can be transmitted sexually, but it can also happen naturally. A leading cause of infertility, PID affects the ovaries, fallopian tubes and uterus and is most common in women ages 15 to 25.

Sometimes it presents without symptoms, but when PID does flare up, it can be confused with ectopic pregnancy or ovarian cysts — or ovulation pain.

PID symptoms include:

  • pain and inflammation in your pelvis
  • nausea and/or vomiting
  • irregular bleeding (outside of your period)
  • changes in your vaginal discharge
  • fever and/or chills
  • pain during urination and/or intercourse

Ectopic pregnancy

An ectopic pregnancy is a serious condition that happens when a fertilized egg implants itself somewhere other than the uterus, such as in a fallopian tube (that’s why it’s also called a tubal pregnancy), your cervix or an ovary.

The pregnancy is not viable, but if the egg keeps growing, it can rupture the fallopian tube, which can cause heavy internal bleeding.

Bleeding and pelvic pain (often on one side, similar to ovulation pain) are common early symptoms of an ectopic pregnancy, so seek medical attention immediately if you experience these or more intense symptoms:

  • severe pain in your abdomen or pelvis, especially on one side
  • abnormal bleeding
  • dizziness or fainting
  • pressure in your rectum

STDs

Pelvic pain can also be a symptom of sexually transmitted diseases or bacterial infections. If your pain is accompanied by vaginal discharge or a fever, consider getting tested. (Even if you’re in a committed relationship, regular STD testing can offer peace of mind.)

Uterine fibroids

Uterine fibroids are benign growths that develop in or on the walls of the uterus. They can cause both severe pain and abnormal (usually heavy) bleeding, though the pain is usually closer to the uterus than the ovaries.

IBS

Pain in your abdomen or pelvis can be hard to pinpoint at times. Irritable bowel syndrome can also cause bloating and pain, though it is usually associated with digestive issues like diarrhea or constipation.

Interstitial cystitis

Interstitial cystitis is a chronic condition characterized by bladder pain, which can be mistaken for pelvic pain (since your reproductive organs and bladder are close neighbors).

IC may also feel like you have to pee all the time, and you might even struggle to hold it at times. Your bladder pain may get worse at certain times during your cycle.

You can deal with your ovulation pain the same way you deal with menstrual pain and cramps.

  • Take over-the-counter (OTC) pain relievers, such as naproxen (Aleve) or ibuprofen (Advil or Motrin).
  • Use a heating pad or take a hot bath.
  • Talk to your doctor about hormonal birth control options that can prevent ovulation (thus eliminating its associated pain).

On its own, ovulation pain isn’t a sign that something serious is going on in your body. And, annoying as it might be, ovulation pain does help you pinpoint your fertile window.

Assume the glass-half-full POV and think of your ovulation pain as a way to stay connected to your fertility and menstrual cycle.

Still, you should contact your healthcare provider if your ovulation pain:

  • changes over time
  • lasts more than 1 to 2 days
  • comes with bleeding (more than spotting)
  • interrupts your daily activities

You should also talk to your healthcare provider if you suspect something more serious, in addition to ovulation pain.

tl;dr

  • Ovulation pain is common — it happens to 1 in 5 people with ovaries.
  • Also known as mittelschmerz or “middle pain,” it’s usually harmless and short-lived.
  • You can treat ovulation pain with OTC meds or a heating pad, or whatever you use to deal with period cramps.
  • Plenty of other (more serious) conditions can cause midcycle pelvic pain, including cysts and PCOS, an ectopic pregnancy, endometriosis, uterine fibroids, PID, STDs and even IBS, or interstitial cystitis.
  • Pelvic pain can be serious. Talk to your doctor if your ovulation pain changes or worsens.