Ovarian cyst (simple, functional and follicular)

A simple or functional ovarian cyst is a fluid-filled sac that forms on the ovary, often as part of the normal menstrual cycle. A follicular cyst forms when a follicle fails to release its egg and continues to grow instead, while other functional cysts can form after ovulation. Most are small, cause no symptoms and resolve on their own within one to three cycles. These cysts are generally considered benign and are usually monitored with a repeat ultrasound rather than treated immediately. Larger cysts, or those causing pain or persisting beyond a couple of cycles, may need further assessment. Functional cysts are common and are different from cysts related to endometriosis or other ovarian conditions.

Also known as: simple ovarian cyst, functional cyst, follicular cyst

Last reviewed: 9 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.