An ovarian cyst is a fluid-filled sac that forms on or inside an ovary. They are extremely common, and the most reassuring fact about them is this: the large majority are harmless, cause no symptoms, and disappear on their own without any treatment.
What is an ovarian cyst?
Your ovaries are two small, almond-shaped organs that release an egg each cycle and produce hormones such as estrogen and progesterone. A cyst is simply a sac of fluid that develops in or on one of them. Most are functional cysts—a normal by-product of ovulation—and they are not cancer. They typically measure a few centimetres, come and go quietly, and resolve within one to three menstrual cycles. Cysts are most common during the reproductive years, but they can occur at any age.
Common types of ovarian cysts
Cysts fall into two broad groups: functional cysts, linked to the menstrual cycle, and other (non-functional) cysts that form for different reasons.
| Type | Group | What it is | Usual outlook |
|---|---|---|---|
| Follicular | Functional | The follicle holding an egg doesn't release it and keeps filling with fluid | Very common; usually clears in weeks |
| Corpus luteum | Functional | The follicle reseals after releasing the egg and fills with fluid or blood; can occur in early pregnancy | Common; usually resolves on its own |
| Dermoid (teratoma) | Other | A growth containing tissue such as skin, hair or fat | Usually benign; may need removal |
| Endometrioma | Other | A cyst formed from endometriosis tissue, sometimes called a “chocolate cyst” | Benign but may cause pain; often needs review |
| Cystadenoma | Other | A cyst growing from cells on the ovary's surface | Usually benign; larger ones may be removed |
Functional cysts are by far the most frequent. The “other” types are less common, usually still benign, but more likely to need monitoring or treatment. A small minority of cysts—particularly those that are large, look complex (with solid areas) on a scan, or appear after menopause—can be cancerous, which is exactly why certain features are watched more closely rather than left alone.
Ovarian cyst symptoms
Most cysts cause no symptoms at all and are found by chance during a scan for something else. When symptoms do appear, they are usually mild and may include:
- Bloating or a feeling of fullness or pressure in the lower abdomen
- Dull pelvic pain or pressure, sometimes on one side
- Pain during sex
- A change in your normal cycle, such as irregular periods or spotting between periods
- Needing to pass urine more often, if a larger cyst presses on the bladder
These symptoms overlap with many ordinary, harmless conditions—which is exactly why a cyst should be assessed rather than self-diagnosed. One pattern is worth knowing, though: persistent bloating, feeling full quickly or struggling to eat, ongoing pelvic or abdominal pain, and needing to urinate urgently or often—if these are new for you and happen on most days for several weeks—should be checked promptly rather than brushed off, because that cluster occasionally points to ovarian cancer. This is uncommon, but it is the reason these symptoms deserve a timely review, not just a wait-and-see.
How ovarian cysts are found and monitored
The main tool is a pelvic ultrasound, often done through the vagina for a clearer view. It shows a cyst's size, whether it is simple (a clean fluid sac) or complex (containing solid areas), and how it changes over time. Because functional cysts usually go away by themselves, the standard approach for a small, simple cyst is watchful waiting—a repeat scan after several weeks or a few months to confirm it has shrunk or disappeared.
In some cases a clinician will add other checks: a pregnancy test (both to guide management and because pelvic pain in pregnancy needs its own assessment), hormone levels, or a blood test such as CA-125. CA-125 can be raised by many benign conditions, so it is interpreted alongside your scan, your symptoms and whether you have been through menopause—not on its own. The features that prompt closer attention are a larger or growing cyst, solid areas seen on the scan, or a new cyst after menopause. Treatment such as keyhole surgery (laparoscopy) is generally reserved for cysts that are large, persistent, painful, or have those features.
Ovarian cysts vs PCOS
A frequent and understandable confusion: having ovarian cysts is not the same as having PCOS. Polycystic ovary syndrome is a hormonal condition diagnosed from a pattern of features—irregular cycles, signs of higher androgen levels (such as acne or extra hair growth), and ovaries with many small follicles—not from one cyst. The “cysts” in PCOS are actually numerous small, immature follicles, not the larger functional cysts described here. You can have an occasional ovarian cyst without ever having PCOS, and vice versa. For more, see our guides on ovarian cysts vs PCOS and PCOS symptoms.
Cysts in pregnancy and after menopause
Cysts can show up at the two ends of the reproductive timeline, and each has its own nuance:
- In pregnancy, a corpus luteum cyst is common in the early weeks and usually settles by itself. If a cyst causes pain—or if pain comes with bleeding—it should be assessed, since being pregnant changes how symptoms are weighed up and a rare rupture can cause significant internal bleeding.
- After menopause, cysts are far less common because functional cysts depend on ovulation. A new cyst or pelvic pain in the postmenopausal years is less likely to be a simple functional cyst and carries a somewhat higher chance of being abnormal, so it deserves prompt evaluation rather than watchful waiting. Most postmenopausal cysts are still benign—this is reassurance with a caveat: they should be checked without delay. If you are unsure where you are in this transition, our guide on menopause age may help.
Ruptured cyst and ovarian torsion: a medical emergency
This is the part to remember. While most cysts are harmless, two complications are emergencies and need urgent or emergency care immediately:
- Ruptured ovarian cyst—a cyst that bursts, sometimes causing sudden sharp pain and, less often, internal bleeding.
- Ovarian torsion—a cyst causes the ovary to twist, cutting off its blood supply. This needs surgery quickly to save the ovary.
Seek emergency help if you have sudden, severe, one-sided pelvic or abdominal pain, especially when it comes with:
- Nausea or vomiting
- Dizziness, faintness, or fainting—or feeling lightheaded when you stand up
- Pain spreading to the shoulder tip (a sign that can accompany internal bleeding)
- Rapid breathing, a racing heartbeat, or cold, clammy skin
Do not wait to see if it passes. A high fever with pelvic pain points more towards an infection than a twisted or burst cyst, but it is still a reason to be seen urgently. One more emergency to know: pelvic pain with a missed period or a positive pregnancy test can signal an ectopic pregnancy (a pregnancy growing outside the womb), with or without bleeding—this also needs urgent assessment.
When to see a clinician
Most ovarian cysts are benign and resolve on their own, so the everyday message is reassuring. Still, book an appointment—and ask for it to be a prompt one—if you have persistent bloating, feeling full quickly, ongoing pain on one side, or urinary urgency that is new and lasts most days for several weeks, or pain with sex, or a cyst that has already been found and needs follow-up. Get prompt review for any new cyst or pelvic pain after menopause, and for pelvic pain in pregnancy. And call emergency services or go to the nearest emergency department for sudden, severe pelvic pain, particularly with nausea, vomiting, dizziness, fainting or shoulder-tip pain—that can mean a ruptured cyst or ovarian torsion. This article is educational and is not a diagnosis; any new or worsening pelvic symptom should be assessed by a qualified clinician.
