The luteal phase is the second half of the menstrual cycle, spanning from ovulation to the start of your next period. It typically lasts about 12 to 14 days. During this time, your body ramps up progesterone production to prepare the uterine lining for a possible pregnancy, and if pregnancy doesn’t happen, falling hormone levels trigger your period.
Where It Fits in Your Cycle
Your menstrual cycle has two main phases. The first half, called the follicular phase, starts on day one of your period and ends when you ovulate. The second half is the luteal phase, which begins immediately after ovulation and ends when your next period starts. While the follicular phase can vary widely in length from cycle to cycle (which is why periods aren’t always perfectly predictable), the luteal phase tends to stay more consistent for each individual.
What Happens Inside Your Body
When an egg is released from the ovary during ovulation, the empty follicle it left behind transforms into a small, temporary gland called the corpus luteum. This structure forms from cells in the follicle wall and becomes a hormone-producing powerhouse. Its primary job is to secrete progesterone, the dominant hormone of the luteal phase.
Progesterone does several important things to the uterine lining. It stimulates the growth of complex glands within the tissue, increases glycogen (stored energy) accumulation, and expands the blood supply by increasing the surface area of small spiral arteries. All of this creates a nutrient-rich environment where a fertilized egg could implant and begin developing.
Estrogen also rises during this phase, though it plays a supporting role. It peaks alongside progesterone around eight or nine days after ovulation, which corresponds to the window when implantation would typically occur. After that peak, the corpus luteum begins to decline. Its function starts winding down 9 to 11 days after ovulation, and if no pregnancy occurs, both progesterone and estrogen drop sharply. That hormonal withdrawal is what triggers your period.
What Happens If You Get Pregnant
If a fertilized egg successfully implants in the uterine lining, it begins producing a hormone called hCG (the same hormone pregnancy tests detect). This hCG signal “rescues” the corpus luteum from its natural breakdown, keeping it alive and producing the progesterone needed to sustain the early pregnancy. Without this rescue, progesterone would fall and the uterine lining would shed. The corpus luteum continues supporting the pregnancy until the placenta develops enough to take over progesterone production, usually around 8 to 10 weeks in.
Why You Feel Different During This Phase
Many of the physical and emotional changes you notice in the days before your period are directly tied to luteal phase hormones. Bloating, breast tenderness, mood changes, fatigue, and food cravings are all common. These premenstrual symptoms arise from the interaction between progesterone and brain chemicals like serotonin and GABA. The prevailing theory is that hormonal fluctuations, particularly a sensitivity to progesterone’s effects on these neurotransmitters, drive PMS rather than any single hormone being “too high” or “too low.”
Progesterone also has a thermogenic effect, meaning it raises your core body temperature. After ovulation, your resting body temperature increases by about 0.3°C to 0.7°C (roughly 0.5°F to 1.3°F). This shift becomes detectable about 24 hours after progesterone starts rising, plateaus within 48 hours, and stays elevated until just before your period, when progesterone drops. This is the basis for basal body temperature tracking: if you measure your temperature first thing each morning, you can identify a sustained rise that confirms ovulation has occurred and the luteal phase has begun.
How to Track Your Luteal Phase
To figure out the length of your luteal phase, you need to know when you ovulate. Basal body temperature charting is one method. Ovulation predictor kits, which detect a surge in luteinizing hormone (LH) in your urine, are another. Once you’ve identified your ovulation day, count the days from the day after ovulation to the day before your next period starts. That number is your luteal phase length.
Tracking over several cycles gives you a more reliable picture, since individual cycles can vary slightly. Most people find their luteal phase stays within a day or two of the same length each time, even when their overall cycle length fluctuates.
When the Luteal Phase Is Too Short
A luteal phase of 10 days or fewer is considered short, a condition sometimes called luteal phase deficiency (LPD). The concern is that the uterine lining doesn’t have enough time under progesterone’s influence to properly support implantation. Possible causes include inadequate progesterone production, insufficient duration of progesterone exposure, or the uterine lining not responding normally to progesterone.
That said, this diagnosis remains controversial in reproductive medicine. The American Society for Reproductive Medicine notes that LPD has not been proven to independently cause infertility or recurrent pregnancy loss. It can even show up in fertile, normally menstruating people. Part of the challenge is measurement: progesterone is released in pulses throughout the day, with levels swinging anywhere from 5 to 40 ng/mL over short periods in normal ovulatory cycles. A single blood draw can easily catch a low point and paint a misleading picture. A level above 3 ng/mL confirms that ovulation happened, but no specific minimum concentration has been established as the cutoff for “normal” luteal function.
If you’re concerned about a consistently short luteal phase, especially while trying to conceive, a healthcare provider can review your cycle tracking data and run bloodwork timed to the mid-luteal window (about 6 to 8 days after ovulation) to get a clearer picture of your progesterone output.