How to track ovulation: tests, apps, temperature and discharge compared

There are four main ways to work out when you’re ovulating: ovulation tests, cycle apps, charting your temperature and watching your discharge. Some are better than others, and you don’t have to use any of them to get pregnant. Here’s how they compare.

Do you need to track ovulation?

Not necessarily. If you have sex every 2 to 3 days, you’ll cover your fertile window without knowing exactly when it is. NICE, which advises the NHS, recommends this approach. Tracking can help if you have sex less often, are using donor sperm, or want to understand your cycle. But some people find it makes trying for a baby stressful, and stress can affect your relationship and your sex drive. Do what works for you.

1. Ovulation tests

How they work: you wee on a stick, like a pregnancy test. It picks up a rise in luteinising hormone (LH), which surges shortly before you ovulate. Once the surge has happened, ovulation usually follows within 12 to 36 hours.

How good are they? They’re the best-studied option. A 2023 Cochrane review looked at women under 40 who’d been trying for less than a year. In 4 trials, timing sex with ovulation tests raised the chance of getting pregnant from about 18% to between 20% and 28%. The one trial that looked at births found a similar benefit. The evidence was moderate quality, and many of the studies were funded by test makers.

Tips: start testing a few days before you expect to ovulate. If your cycles are irregular you’ll probably need more sticks. Read the instructions, as tests vary.

2. Cycle and fertility apps

How they work: most apps predict your fertile days from the dates of your past periods. Some also let you add temperatures, discharge or ovulation test results.

How good are they? Apps that only use period dates are the least reliable option. In a 2016 study of 53 apps and websites, only 4 predicted the correct fertile window, and most included days after ovulation, when pregnancy is unlikely. Ovulation moves from cycle to cycle, so a prediction based on averages can miss it. Apps don’t test whether you’ve actually ovulated, and none are officially recommended by the NHS. An app is more useful as a diary for the other signs than as a predictor on its own.

3. Charting your temperature

How it works: take your temperature every morning before you get out of bed, at the same time each day and before eating or drinking. After ovulation it rises by around 0.2°C.

How good is it? It only suggests you’ve ovulated after it’s happened, by which point most of your fertile window has passed. It can’t help you time sex this month, and NICE says temperature charts aren’t reliable enough to confirm ovulation. If you’re worried you’re not ovulating, ask your GP about a blood test.

4. Watching your discharge

How it works: notice your discharge each day. In the days before ovulation it becomes wetter, more slippery and stretchy, like raw egg white. That’s your most fertile time.

How good is it? It’s free and gives you advance notice, which temperature doesn’t. It takes a couple of cycles to learn to read the changes.

Combining methods

Using more than one sign at once is more reliable than any one alone. Fertility awareness methods that combine temperature, discharge and cycle dates take 2 to 3 cycles to learn properly. Ovulation tests plus watching your discharge is a simple combination to start with.

Tests your GP can do

If you’re not sure you’re ovulating, especially if your periods are irregular, your GP can arrange a blood test for progesterone to check. Clinics can also use ultrasound scans to watch the follicle that holds the egg develop, usually as part of fertility treatment.

Questions people ask

When should I start using ovulation tests?

A few days before you expect to ovulate, so count back from when your next period is due. The instructions usually tell you which day to start for your cycle length. With irregular cycles you may need to test for more days.

Can ovulation tests be wrong?

Yes. A positive result shows the LH surge, not that an egg has definitely been released. If you test for 5 days, there’s about an 80% chance of catching the surge, rising to about 95% with 10 days of testing.

Do ovulation tests work if my periods are irregular?

They can still help you pinpoint ovulation, but you may end up using more test sticks. If your periods are very irregular or have stopped, see your GP.

Should we only have sex on fertile days?

You don’t have to. NICE advises sex every 2 to 3 days, which takes the pressure off timing.