The part of the menstrual cycle after ovulation until the next period, usually 12 to 14 days.
What the luteal phase is
The luteal phase is the second half of the menstrual cycle. It begins just after ovulation, when the ovary releases an egg, and ends when the next period starts. For most women this stretch lasts about 12 to 14 days, though it can vary a little between individuals. The luteal phase is one of the two main parts of the menstrual cycle, paired with the follicular phase that comes before ovulation. Understanding this split helps explain what happens in the body at each stage of the cycle.
The role of progesterone
Once an egg is released, the follicle left behind in the ovary turns into a structure called the corpus luteum. This corpus luteum produces progesterone, the hormone that stabilises the uterine lining so it is ready to support a possible pregnancy. If no pregnancy occurs, the corpus luteum stops working, progesterone levels fall, and a period begins. The luteal phase therefore only exists once true ovulation has happened. To understand the role of these hormones further, see the hormones page.
Why it matters for PCOS
In PCOS, irregular or absent ovulation makes the luteal phase hard to identify, because it only begins after ovulation. When long cycles happen without ovulation, less progesterone is produced, which is part of why periods become irregular. For those planning around fertility, an unpredictable luteal phase makes the fertile window harder to track. The link between ovulation and periods is explained further on the what is PCOS page.
When to talk to a doctor
A blood progesterone test timed to the right point in the cycle can help show whether ovulation occurred. However, the timing of this test depends on your cycle length, and interpreting it is not simple if your cycles are irregular. If you use home cycle tracking, the results can be a guide but not a confirmation, because home tools have their limits. For this reason, a doctor is best placed to decide when a test should be done and what it means for your situation, rather than reading it on its own.
This glossary is education, not diagnosis. For your own situation, ask a doctor or pharmacist.