Quick answer: The five main signs of ovulation are: a surge in LH (detected by an ovulation predictor kit), a change in cervical mucus (clear, slippery, egg-white consistency), a slight rise in basal body temperature, a twinge of one-sided pelvic pain (mittelschmerz), and a subtle increase in libido. The LH surge is the most reliable single indicator, occurring 24–36 hours before ovulation.
LH surge: the most reliable sign
Luteinising hormone (LH) surges sharply 24–36 hours before ovulation — the ovary responds to this signal by releasing the egg. Ovulation predictor kits (OPKs) detect LH in urine and give a positive result in this window. Testing once or twice daily from day 10 of a 28-day cycle (earlier if your cycles are shorter) captures the surge reliably. A positive OPK means ovulation is likely within the next 24–36 hours — the most fertile period for conception is the day of the surge and the following day.
Cervical mucus changes
Cervical mucus changes predictably across the cycle under oestrogen and progesterone influence. At the approach to ovulation, oestrogen rises and mucus becomes clear, slippery, and stretchy — similar in appearance and texture to raw egg white. This fertile-quality mucus facilitates sperm movement through the cervix and can keep sperm viable for up to 5 days. After ovulation, progesterone rises and mucus becomes thicker and opaque. Checking cervical mucus daily by wiping before urinating provides a reliable chart of the fertile window over time.
Basal body temperature (BBT)
BBT rises by 0.2–0.5°C after ovulation and remains elevated until the next period. This post-ovulatory rise is caused by progesterone. BBT charting confirms that ovulation has occurred — it does not predict it in advance. To use BBT effectively: take temperature every morning before getting out of bed at the same time, using a basal thermometer accurate to 0.1°C. After 2–3 months of charting, the pattern shows when in your cycle ovulation consistently occurs, allowing better prediction in subsequent cycles.
Mittelschmerz (ovulation pain)
Around 20% of women experience mittelschmerz — a one-sided lower abdominal ache or twinge occurring at or around ovulation, lasting from minutes to a few hours. It is caused by the follicle expanding and rupturing. The side varies month to month depending on which ovary releases the egg. Mittelschmerz is a useful confirming sign but not reliable enough to use alone for timing — some women never experience it, and similar pain can have other causes.
Frequently Asked Questions
How long does the fertile window last?
The fertile window is approximately 6 days: the 5 days before ovulation (sperm can survive up to 5 days in fertile cervical mucus) and the day of ovulation itself (the egg survives 12–24 hours). The 2–3 days immediately before ovulation and the day of are the most fertile. After ovulation, the chance of conception drops sharply within 12–24 hours.
Can you ovulate without any noticeable signs?
Yes — not all women notice ovulation symptoms, and symptom intensity varies month to month. OPKs are the most reliable way to identify the fertile window for women who don’t experience clear physical signs. If cycles are irregular or ovulation signs are absent over several months, discuss with your doctor — anovulatory cycles (cycles without ovulation) can be a sign of hormonal conditions including PCOS.
Does ovulation always happen on day 14?
No — day 14 is the average for a textbook 28-day cycle, but cycles vary significantly. Ovulation occurs approximately 14 days before the next period, not 14 days after the last one. For a 35-day cycle, ovulation is likely around day 21. For a 24-day cycle, around day 10. Tracking LH or cervical mucus is more accurate than counting days, particularly for women with irregular cycles.
Related Reading
- Your body at 1 week pregnant: what’s really happening
- 2 weeks pregnant: ovulation, conception & early signs
- 3 weeks pregnant: implantation and the very first symptoms
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