One of the most common symptoms of polycystic ovary syndrome (PCOS) is irregular menstrual periods. In PCOS, changes in the menstrual cycle usually reflect hormonal imbalance in the body. These hormone disturbances affect the endocrine system (the hormone control system of our body) and can lead to irregular periods, fertility problems and severe premenstrual symptoms.
Irregular cycles mean periods may not follow a predictable schedule. Most women have a menstrual cycle of about 28 days. In PCOS, cycles may range from 21 to 40 days, or periods may be missed completely. When menstrual bleeding does occur, it is often heavier than usual. Most women lose about 2–3 tablespoons of blood during a period, but women with PCOS may bleed about twice as much and may also pass blood clots. Period pain may also be more intense. These symptoms can interfere with daily life. Heavy bleeding, pain and uncertainty about when a period will occur can affect physical comfort, emotional well-being and overall quality of life.
Irregular or absent periods often indicate that ovulation (release of an egg from the ovary) is not occurring regularly, which can make pregnancy difficult.
PCOS affects the menstrual cycle mainly through hormone imbalance. Many women with PCOS have high levels of androgens (male-type hormones such as testosterone), which can interfere with normal menstrual function.
Insulin (a hormone that controls blood sugar levels) also plays a role. Most women with PCOS have insulin resistance (a condition where the body does not respond properly to insulin). This leads to higher insulin levels, which can increase testosterone production in the ovaries. High insulin and high testosterone can contribute to weight gain, high blood pressure and irregular or heavy periods.
Restoring regular menstrual cycles is a key goal for reproductive health. Managing these hormonal imbalances supports overall health and long-term well-being.
Reference: PCOS weight loss. What are periods like with PCOS? Available from: https://pcosweightloss.org/what-are-periods-like-with-pcos/. Accessed on: 12 February 2026.