What is mittelschmerz?

Mittelschmerz is the medical name for ovulation pain: a one-sided pain low in the tummy at or around the time an egg is released. MedlinePlus, from the US National Library of Medicine, also calls it midcycle pain. The NHS says it is common, usually lasts a short time and is nothing to worry about.

Estimates of how many people get it vary: one in five women, says MedlinePlus; about 40%, says the Victorian Government's Better Health Channel in Australia; over 40% of women of reproductive age, often almost every month, says a StatPearls review. StatPearls adds that it generally does not start until a few years after periods begin, once regular ovulation is established.

This page is for anyone who feels a twinge mid-cycle and wants to know whether it is ovulation, and what else it could be.

When does ovulation pain happen?

Around the middle of your cycle. The NHS says it happens about 14 days before a period, and StatPearls places it between days 7 and 24 of the cycle. The exact timing is debated. StatPearls says the pain coincides with the peak in luteinising hormone (LH), while the follicle is still enlarging and has not yet burst, which makes it a pre-ovulatory symptom. MedlinePlus says it may come just before, during or after ovulation.

Either way it falls close to your fertile days, and MedlinePlus notes it may help you know when the egg is released. More reliable signs are in how to track ovulation and understanding cervical mucus; the ovulation and fertile window calculator estimates your dates, and menstrual cycle phases shows where ovulation sits.

Ovulation pain on the left or right side: does it switch?

It affects one side at a time, the side of the ovary that is releasing an egg; StatPearls says it is felt on the same side as the developing follicle. The sources differ on the pattern. The NHS says it switches sides each time, depending on which ovary releases the egg. MedlinePlus says it may switch from month to month but can also stay on the same side for many months in a row. So the same side two months running is not a warning sign by itself.

Right-sided pain deserves one extra thought, because of appendicitis. The NHS says appendicitis pain usually starts around the belly button, then moves to the lower right side over a few hours and gets worse. Moving or coughing may make it worse, and it can come with feeling sick, loss of appetite or a high temperature.

What does ovulation pain feel like, and how long does it last?

Usually a short-lived ache or twinge. Three health services describe it:

	NHS (UK)	MedlinePlus (US)	Better Health Channel (Australia)
Feels like	A dull pain or sharp, sudden twinges	A sharp, cramping pain unlike other pain; severe pain is rare	Pressure, twinges, sharp pains, cramps or strong pain
Lasts	A few minutes to 1 or 2 days	Minutes to a few hours; can last up to 24 to 48 hours	A few minutes to a couple of days
Other signs	A little vaginal bleeding or discharge	Contact a provider if the pain changes, lasts longer than usual or comes with vaginal bleeding	See a doctor if it lasts longer than 3 days or comes with heavy bleeding or discharge

What causes ovulation pain?

The NHS says it is caused by the ovary releasing the egg, but the exact mechanism is not settled. Three explanations appear in the sources:

the growing follicle stretching the surface of the ovary just before ovulation (MedlinePlus and the Better Health Channel)
fluid or blood released from the burst follicle irritating the lining of the abdomen (MedlinePlus)
the LH surge making the smooth muscle around the follicle contract, through prostaglandins (StatPearls, which considers simple stretching an unlikely cause)

What else causes pain mid-cycle?

The NHS lists conditions that can cause a similar pain: endometriosis, ovarian cysts, some sexually transmitted infections such as chlamydia, scar tissue (adhesions) from surgery near the ovaries such as a caesarean, and ectopic pregnancy. The ones to recognise:

Condition	What points to it (NHS)	What to do (NHS)
Ectopic pregnancy	You could be pregnant, even without a positive test; pain low down on one side; bleeding that starts and stops and may be watery and dark brown; shoulder tip pain; pain when pooing or peeing. Usually between weeks 4 and 12.	GP or NHS 111. Sudden, sharp, intense pain with dizziness or fainting and feeling sick: 999 or A&E
Appendicitis	Pain starting around the belly button, moving to the lower right and worsening; feeling sick; high temperature	Urgent GP or 111 if it is getting worse or moves to the lower right; severe pain: 999 or A&E
Ovarian cyst that bursts or twists	Pelvic pain ranging from a dull, heavy feeling to sudden, severe and sharp	Urgent GP or 111 for sudden severe pain, or pain with feeling or being sick
Endometriosis	Listed by the NHS as a cause of similar pain	See a GP if the pain keeps coming back; see what is endometriosis
Pelvic infection, such as chlamydia	Listed by the NHS as a cause of similar pain	NHS 111 if pelvic pain comes with unusual discharge or a very high temperature

More on the first of these: ectopic pregnancy. If you already know you are pregnant, see cramping in early pregnancy.

What helps ovulation pain?

If ovulation is the only cause and the pain is not severe, the NHS says a warm bath or painkillers such as paracetamol or ibuprofen may be all you need; the Better Health Channel suggests a heat pack or hot water bottle. Ask a pharmacist which painkiller suits you, particularly if you could be pregnant. If you are not trying to conceive, the NHS says a GP may suggest contraception that stops ovulation, such as the pill or an implant.

When to get help

The NHS advice:

Ask for an urgent GP appointment or contact NHS 111 if you have tummy pain and it is severe and painkillers have not helped, it keeps coming back, or you think you may be pregnant.
Call 999 or go to A&E if pelvic pain is severe, getting worse or hurts when you move or touch the area; you feel faint, dizzy or lightheaded, or pass out; you have pain in the tip of your shoulder; you have difficulty breathing; you have heavy bleeding from your vagina; or you suddenly feel confused.
Outside the UK, call your local emergency number for the same symptoms. The Better Health Channel says to see a doctor if ovulation pain is severe or lasts longer than 3 days.

Frequently asked questions

What does ovulation pain feel like?

The NHS describes a dull pain or sharp, sudden twinges on one side of your lower tummy, lasting from a few minutes to 1 or 2 days. MedlinePlus calls it a sharp, cramping pain unlike other pain and says severe pain is rare. Some people also notice a little vaginal bleeding or discharge around the same time.

Does ovulation pain mean you are more likely to get pregnant?

Not on its own. It signals that ovulation is near, within your fertile days, so it can help you time sex. None of the sources here links the pain to better chances, and with estimates of who feels it from one in five to about 40%, not feeling it says nothing about whether you ovulate.

Can you have ovulation pain on both sides?

The NHS, MedlinePlus and StatPearls all describe ovulation pain as one-sided, on the side of the ovary releasing an egg, so pain on both sides at once is not the pattern they describe. If you get it, especially if it is severe, keeps coming back or you could be pregnant, follow the NHS advice above and get it checked.

Is ovulation pain a sign of endometriosis?

Usually not: the NHS says ovulation pain is common and nothing to worry about. But it lists endometriosis among conditions that cause a similar pain, and the Better Health Channel says severe pain could point to it. Raise severe or monthly pain with a GP; see trying to conceive with endometriosis.

Ovulation Pain (Mittelschmerz): Timing, Side and When to Worry