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How Do Ovulation Test Kits Work?

Ovulation is when an egg is released from one of your ovaries into the fallopian tube ready to be fertilised by sperm and this is when a woman is fertile. Once released the egg only lives for 12-24 hours so identifying when you are going to ovulate will help you to time sex. If you miss this window then you will need to wait another cycle, which on average is 28 days but can be much shorter or longer for some women.

Just before ovulation, approx. 24-36 hours before1, the level of luteinizing hormone (LH) in the woman’s body increases. Ovulation test kits identify this surge in LH to help pinpoint when you are going to ovulate.

Do ovulation test kits work?

Ovulation calculator’s and apps give an indication of when you might ovulate based on a woman’s average cycle length, however, this may differ each cycle for some women. Ovulation test kits pinpoint exactly when you ovulate to help you to time sex, which ultimately maximises your chances of conceiving.

What types of ovulation tests are available?

There are two main formats:

1. Ovulation Mid-Stream Tests
With mid-stream tests you hold the test in your urine stream for a few seconds. When you’ve finished just put it on the side and wait for the results. Non-digital ovulation tests will show the result using lines. One line will be the control line to show the test is working and if the test detects LH it will show another line. This line will get darker the more LH it detects.


Digital tests like the Clearblue digital ovulation test will simply show a smiley face if it detects LH and if not it will just be a circle. A lot of people really like the digital because it just makes it really clear and easy to understand whether you are ovulating or not. With the visual tests you are tracking the darkness of the line and when it is as dark as the control line that’s when you are going to ovulate. The more you test, the more confident you’ll become at reading the results.


2. Ovulation Test Strips
Test strips require you to urinate into a small container and then you simply dip the strip into the urine for a few seconds. These also require you to track the darkness of the results line against the control line. The main advantage of these type is the low cost because you aren’t paying for the packaging and brand. If you are doing a lot of testing because you have irregular cycles then these are a good option. Some people find it a bit inconvenient having to urinate in a container, however others may struggle to get their aim right with a midstream! 


When to use an ovulation test?

In terms of when to test, it is recommended to test for 5 days prior to your predicted ovulation date, however, women who have irregular cycles each month may test over a longer period. It is recommended that the optimal testing time is between 10am and 3pm, ideally when you haven't had any fluids for 2 hours, and you should test the same time every day.

It’s really down to what is right for you. You may want to try both ovulation midstream tests and test strips to discover which works best for you.



1. Ferreira-Poblete A. The probability of conception on different days of the cycle with respect to ovulation: an overview. Adv Contracept 1997 Jun;13(2-3):83-95.