The ovulation cycle is the monthly process your body goes through to prepare, release, and either fertilize or shed an egg. A full cycle averages 28 days but can range from 21 to 35 days, and ovulation itself is a single event lasting only minutes, though the hormonal shifts that drive it unfold over weeks. Understanding how each phase works helps whether you’re trying to get pregnant, avoid pregnancy, or simply make sense of what your body does every month.
The Two Main Phases of Your Cycle
Your cycle is divided into two halves by ovulation: the follicular phase (before the egg releases) and the luteal phase (after). These phases behave quite differently.
The follicular phase begins on the first day of your period and lasts anywhere from 14 to 21 days. During this stretch, your brain sends signals to your ovaries to start developing small fluid-filled sacs called follicles, each containing an immature egg. Eventually one follicle outpaces the rest and becomes the “dominant” follicle, which will mature a single egg for release. How long this process takes varies from person to person and even cycle to cycle, which is why period timing isn’t always predictable.
The luteal phase picks up right after ovulation and lasts about 14 days. Unlike the follicular phase, it stays fairly consistent in length. During this time, the ruptured follicle transforms into a temporary structure that pumps out progesterone, thickening the uterine lining in preparation for a possible pregnancy. If no fertilized egg implants, progesterone drops, and the lining sheds as your period, restarting the cycle.
How Hormones Trigger Ovulation
Ovulation doesn’t happen randomly. It’s the result of a carefully timed hormonal chain reaction involving your brain and your ovaries working in a feedback loop.
Early in the follicular phase, the hypothalamus (a control center in your brain) sends pulses of a signaling hormone to the pituitary gland, which responds by releasing two key hormones into your bloodstream: one that stimulates follicle growth and one called LH. As the dominant follicle matures, it produces rising levels of estrogen. That climbing estrogen does something counterintuitive: at first it suppresses LH, but once estrogen reaches a critical threshold, it flips the switch and triggers a massive surge of LH instead.
This LH surge is the final trigger. Within about 24 to 36 hours of the surge, the dominant follicle ruptures and releases the mature egg into the fallopian tube. The timing is precise enough that home ovulation tests are built around detecting this surge in urine.
Your Fertile Window
Despite ovulation being a single moment, your fertile window stretches over several days because sperm and eggs have different lifespans. Sperm can survive inside the uterus and fallopian tubes for three to five days. A released egg, by contrast, lives for less than 24 hours. The highest pregnancy rates occur when sperm and egg meet within four to six hours of ovulation.
This means the fertile window opens roughly five days before ovulation and closes about a day after. The most likely days for conception are the two to three days leading up to ovulation, since sperm are already in position when the egg arrives. If you’re tracking fertility, that pre-ovulation window matters more than ovulation day itself.
Physical Signs of Ovulation
Your body gives several observable clues that ovulation is approaching or has just occurred.
Cervical mucus changes. As ovulation nears, discharge becomes wet, stretchy, and slippery, often compared to the look and feel of raw egg whites. This shift is driven by rising estrogen, and it serves a biological purpose: the slippery texture makes it easier for sperm to travel through the cervix and into the uterus. You’ll typically notice this egg-white mucus for about three to four days. Before and after that window, mucus tends to be thicker, stickier, or barely noticeable.
Basal body temperature. After ovulation, your resting body temperature rises slightly, typically less than half a degree Fahrenheit. The increase can be as small as 0.4°F or as large as 1°F. The catch is that this shift confirms ovulation only after it has already happened, so tracking temperature over several cycles helps you predict future patterns rather than identify the current moment of ovulation in real time.
Ovulation pain. Up to 40% of people who ovulate experience mid-cycle pain, sometimes called mittelschmerz. It usually feels like a mild twinge or a sudden, sharp sensation on one side of the lower abdomen, corresponding to whichever ovary released the egg that month. It can last minutes to hours and is considered normal.
How to Track Ovulation
Home ovulation predictor kits detect the LH surge in your urine. When used carefully, they reliably detect LH about 9 times out of 10, according to FDA data. A positive result means ovulation is likely within the next day or two. Some newer kits also measure a form of estrogen, giving a wider heads-up that ovulation is approaching.
Cervical mucus monitoring costs nothing and, with practice, gives a useful real-time signal. Checking for that egg-white consistency each day can help you identify your fertile window without any products. Many people combine this with temperature tracking: mucus tells you ovulation is coming, and the temperature rise confirms it happened.
Calendar-based methods are the least reliable because they assume a predictable cycle length. Since the follicular phase can vary by a week or more, counting days alone often misidentifies the fertile window, especially if your cycles are irregular.
When Ovulation Doesn’t Happen
Skipping ovulation in a given cycle, called anovulation, is more common than most people realize. Occasional anovulatory cycles can happen to anyone, but chronic anovulation points to an underlying issue that’s worth investigating.
Hormone imbalances are the most frequent cause. Polycystic ovary syndrome (PCOS) disrupts the normal hormonal signaling needed to mature and release an egg. Thyroid disorders, particularly an underactive thyroid, can also interfere with ovulation. Being significantly above or below a healthy weight affects hormone levels enough to suppress ovulation, as body fat plays a direct role in estrogen production. Chronic stress is another recognized factor because stress hormones can disrupt the precise pulsing of signals from the brain that kick-starts each cycle. Certain medications, including some anti-seizure and antipsychotic drugs, can cause anovulation as a side effect.
Signs that you may not be ovulating include very irregular or absent periods, cycles consistently shorter than 21 days or longer than 35, and the absence of typical ovulation signs like cervical mucus changes or a temperature shift. Blood tests measuring hormone levels at specific points in your cycle can confirm whether ovulation is occurring.