--- title: "How to use an ovulation test: when to test, how to read it" description: "When to start an ovulation test, what time to test, and when it is really positive. How LH works, your fertile days, and what the test cannot tell you." url: https://myperiod.app/en/blog/ovulatietest-gebruiken lang: en date: 2026-10-18 publisher: PERIOD. B.V., Amsterdam --- [Back to blog](https://myperiod.app/blog) [Your cycle](https://myperiod.app/blog/categorie/cyclus) · 7 min read # How to use an ovulation test: when to test, how to read it [Lees dit artikel in het Nederlands](https://myperiod.app/blog/ovulatietest-gebruiken) PERIOD. team · October 18, 2026 **Short answer:** an ovulation test measures the hormone LH in your urine. Just before ovulation LH rises sharply. A positive test means ovulation probably comes within about 12 to 36 hours. Start testing a few days before your expected ovulation, test every day at about the same time, and only call the test positive when the test line is as dark as the control line or darker. ## How an ovulation test works Every cycle your brain sends a surge of luteinising hormone, LH, to your ovaries. That surge is the starting signal for ovulation: shortly after, the egg is released. An ovulation test picks up that surge in your urine. Good to know: there is always a little LH in your body. That is why you see a faint line almost every day. That is not a positive test. Only when the surge comes does the test line get as dark as the control line or darker. Digital tests read that for you and show a symbol. ## When to start testing Ovulation happens about 14 days before your next period. Many manufacturers therefore advise starting on **cycle day = your cycle length minus 17**. That way you start a few days before the expected surge and do not miss it. - 26 day cycle: start on day 9. - 28 day cycle: start on day 11. - 32 day cycle: start on day 15. Day 1 is the first day of your period. If your cycle is irregular, use your shortest cycle of recent months and expect to need more tests. How to find your cycle length is in [when will I get my period](https://myperiod.app/en/blog/wanneer-word-ik-ongesteld). The maths behind ovulation is in [calculating ovulation](https://myperiod.app/en/blog/eisprong-berekenen). ## What time of day to test Unlike a pregnancy test, first morning urine is not always best. LH often rises in the early morning and shows up in your urine a few hours later. Many manufacturers therefore advise testing somewhere between late morning and early evening. A few practical rules: - Test every day at about the same time. - Do not pee for about four hours and do not drink a lot in the two hours before. Diluted urine can hide a surge. - Around the expected surge you can test twice a day. Some surges are short. - Always follow the leaflet of your brand. Waiting and reading times differ. ## Your test is positive. Now what? You are now at your most fertile. The chance of pregnancy is highest if you have sex on the day of the positive test and the day after. Sperm can survive up to about five days, so sex in the days before counts too. Your fertile window is about six days in total. After the surge there is no need to keep testing that cycle. LH can stay high for a day or two, which tells you nothing new. ## A note the NHS makes The NHS advises couples trying for a baby to have sex every two to three days throughout the cycle, rather than timing everything to a test. That gives a good chance and takes the pressure off. So an ovulation test is a tool, not a requirement. If testing makes you anxious, it is fine to stop. ## What an ovulation test cannot tell you - **Whether ovulation actually happened.** An LH surge is the starting signal, not proof. A rise in your [basal body temperature](https://myperiod.app/en/blog/basale-lichaamstemperatuur-cyclus) after ovulation confirms afterwards that it did. - **With PCOS.** Women with PCOS often have higher LH, so a test can look positive more often without ovulation following. See [PCOS explained](https://myperiod.app/en/blog/pcos-uitleg-symptomen). - **Around menopause** and just after stopping the pill LH can behave differently too. - **During fertility treatment** with hormones the test can be misleading. Follow your clinic's advice. - **As contraception** an ovulation test does not work. It shows when you are most fertile, not when you are safe. ## Combine the test with what your body shows The test works best together with other signs. Clear, slippery, stretchy cervical mucus is a strong sign that ovulation is close. Some women feel a mild pain on one side of the lower belly. Read [recognising ovulation symptoms](https://myperiod.app/en/blog/ovulatie-symptomen-herkennen). Keep your test results, mucus and temperature in one place and after a few cycles you see your own pattern. PERIOD. calculates your fertile days from your own cycles and lets you log those signs per day. Your data stays in the EU and is [never sold](https://myperiod.app/free). ## When to see a doctor Trying for a year, or never seeing a positive test cycle after cycle? See your doctor. If you are 35 or older, go after six months. And if your cycle is very irregular or your period stays away, do not wait that long. Read also [how long it takes to get pregnant](https://myperiod.app/en/blog/hoe-lang-duurt-zwanger-worden). *Sources: NHS, Trying to get pregnant and Periods and fertility in the menstrual cycle; ACOG, Evaluating Infertility and Fertility Awareness Based Methods; Thuisarts.nl (Dutch College of General Practitioners), Getting pregnant. This article is general information and not medical advice.* ## FAQ ### When should I take an ovulation test? Start on the cycle day equal to your cycle length minus 17. With a 28 day cycle that is day 11. Test every day until you get a positive result. ### When is an ovulation test positive? When the test line is as dark as the control line or darker. A faint line is normal and does not mean an LH surge yet. ### How long after a positive ovulation test do you ovulate? Usually within about 12 to 36 hours. Sex on the day of the positive test and the day after gives the best chance of pregnancy. ### Can I use first morning urine for an ovulation test? You can, but many manufacturers advise later in the day, because LH only shows up in your urine a few hours after it rises. Check the leaflet of your test. **Want your fertile days and test results in one place? [Download PERIOD. on the App Store](https://apps.apple.com/us/app/period-cycle-period-tracker/id6757947793) or [on Google Play](https://play.google.com/store/apps/details?id=app.myperiod.android).** Want to understand your cycle better? [Why PERIOD. is the period tracker that never sells your data](https://myperiod.app/free) ## Keep reading [Best app for period and ovulation tracking (2026)Tracking your period and ovulation in one app: what an app can and cannot know, which measurements really help, and how Flo, Clue, Natural Cycles and PERIOD. approach it.Read more](https://myperiod.app/blog/best-app-period-and-ovulation-tracking)[Trying to conceive: when do you switch from a cycle app to a pregnancy app?Short answer: preferably never. The moment you switch is exactly when your cycle data is worth the most. What you lose, what you need, and how it fits in one app.Read more](https://myperiod.app/en/blog/van-cyclus-app-naar-zwangerschapsapp-wanneer-overstappen)[Cycle app on the pill: is tracking still worth it when you use contraception?Short answer: yes, but for a different reason than you think. On the pill you do not predict ovulation, but you do track complaints, bleeding and what happens when you stop.Read more](https://myperiod.app/en/blog/cyclus-app-met-de-pil-heeft-het-zin)