Your body gives several signals that ovulation is approaching or has just happened, ranging from changes in vaginal discharge to a slight rise in body temperature. No single sign is perfectly reliable on its own, but tracking two or three together gives most people a clear picture of their fertile window each cycle.
Cervical Mucus Is the Earliest Daily Signal
The most practical sign of approaching ovulation is a change in cervical mucus, the discharge produced by glands in your cervix. In the days after your period, you may notice very little discharge, or it may feel sticky and thick. As ovulation gets closer, rising estrogen levels cause that mucus to become wetter, more slippery, and stretchy. At its most fertile, it looks and feels like raw egg whites.
This isn’t just a visual clue. The slippery texture has a biological purpose: it creates channels that help sperm travel through the cervix and into the uterus. When you notice this type of discharge, ovulation is likely within the next day or two. You can check by wiping with toilet paper before urinating or by inserting a clean finger and observing whether the mucus stretches between two fingers. After ovulation, discharge typically dries up again or becomes thicker and cloudier.
Ovulation Predictor Kits Detect the LH Surge
Ovulation predictor kits (OPKs) are urine tests that detect luteinizing hormone, the hormone your pituitary gland releases in a burst right before the egg is released. Ovulation typically happens 36 to 40 hours after this LH surge begins, so a positive test tells you you’re about to ovulate rather than that you already have.
Most kits work like a pregnancy test: you hold a strip in your urine stream or dip it in a collected sample, then read the result after a few minutes. A positive result means your LH has crossed the kit’s threshold, and your most fertile window is the next 24 to 48 hours. For best results, test in the early afternoon rather than first thing in the morning, since LH tends to surge during the day and takes a few hours to appear in urine.
One important caveat: these kits can be unreliable if you have polycystic ovary syndrome (PCOS). People with PCOS often have consistently elevated or erratic LH levels throughout their cycle, not just before ovulation. Research published in the Journal of Medicine and Life found that people with PCOS had average LH levels of about 12 IU/mL outside of ovulation, compared to roughly 2 IU/mL in people without the condition. That baseline elevation can trigger false positives, making the kit show a “surge” even when no egg is about to be released.
Basal Body Temperature Confirms Ovulation After the Fact
Your resting body temperature shifts slightly after you ovulate. The increase is small, typically less than half a degree Fahrenheit (about 0.3°C), but it’s consistent enough to track. The catch is that this temperature rise happens after the egg has already been released, so it confirms ovulation rather than predicting it. Over several months of tracking, though, the pattern can help you anticipate when ovulation is likely in future cycles.
To get useful data, you need to take your temperature at the same time every morning before getting out of bed, talking, or drinking anything. A regular thermometer works, but a basal body thermometer reads to an extra decimal place, which makes the small shift easier to spot. You’re looking for a sustained rise over at least three consecutive days compared to the previous six. Illness, poor sleep, alcohol, and even sleeping with your mouth open can all throw off the reading on a given day, so expect some noise in the data.
Ovulation Pain and Other Physical Signs
Some people feel a twinge or cramp on one side of their lower abdomen around the time of ovulation. This is sometimes called mittelschmerz (German for “middle pain”). It occurs on the side of the ovary releasing the egg and can last anywhere from a few minutes to a day or two. Some people feel it every month, while others notice it only occasionally or not at all.
Other signs you might notice around ovulation include mild breast tenderness, a slight increase in sex drive, and light spotting. Your cervix itself also changes: during ovulation it tends to sit higher in the vaginal canal, feel softer, and open slightly compared to its firmer, lower position earlier in the cycle. These signs are subtle, and most people only notice them if they’re actively paying attention over multiple cycles.
How Long the Fertile Window Actually Lasts
Once released from the ovary, an egg survives in a viable state for only 12 to 24 hours. That’s a surprisingly narrow window. Sperm, however, can survive inside the reproductive tract for up to five days under the right conditions, which is why the fertile window extends to roughly six days total: the five days before ovulation and the day of ovulation itself. The most fertile days are the two to three days leading up to egg release, when sperm are already in place and waiting.
This is why methods that predict ovulation (cervical mucus changes, LH testing) tend to be more useful for timing than methods that confirm it after the fact (temperature tracking). Ideally, you’d combine a predictive method with a confirmatory one. For example, start testing with OPKs when your cervical mucus begins to change, then use temperature tracking to verify that ovulation actually occurred.
Saliva Ferning Tests: Limited Reliability
You may have seen small microscope-like devices marketed as ovulation tests that use saliva instead of urine. The idea is that rising estrogen near ovulation changes the salt content of your saliva, causing it to dry in a fern-shaped crystalline pattern when viewed under magnification. The FDA notes that this method has real limitations: not everyone produces a visible fern pattern, and ferning can be disrupted by smoking, eating, drinking, or brushing your teeth beforehand. Some people fern on certain fertile days but not others, and ferning can even occur during pregnancy or in men. The FDA specifically advises against using saliva tests to prevent pregnancy because of their unreliability.
Putting the Signs Together
No single ovulation sign works perfectly in isolation. Cervical mucus gives you a real-time, no-cost daily indicator but requires you to learn your own pattern. OPKs give a clear positive-or-negative result but can mislead people with hormonal conditions like PCOS. Temperature tracking builds a reliable long-term picture but only tells you what already happened. The most accurate approach is layering two or three of these methods so they cross-check each other.
If you’re new to tracking, cervical mucus observation is the easiest place to start because it requires no equipment and provides information in the moment. Add OPK testing during the days when your mucus starts to become wet and stretchy, and you’ll have a strong sense of your fertile window within one or two cycles. Temperature tracking adds a layer of confirmation that’s especially useful if your cycles are irregular or if you want to build a longer-term record of your ovulation patterns.