How to use Ovulation Predictor Kits?

By Juliana Kassianos, Transformational Fertility Coach, Yoga Teacher and Founder of The School of Fertility


Urine-based Ovulation Predictor Kits (OPKs) detect the presence of certain hormones in your urine. They work differently depending on which brand you buy. Some just detect luteinising hormone (LH), whilst others detect oestrogen as well. Why these two hormones? Oestrogen rises in the days before you have an LH surge as it prepares your body for ovulation. The LH surge occurs about 24-36 hours before you ovulate, which is when an egg is released from your ovary.


By using ovulation tests, you can identify when your most fertile and when you’re going to ovulate, to make sure you have sex within this period, improving your chances of conceiving. This can be of benefit if:

  • You have irregular periods and aren’t too sure when you ovulate

  • You and your partner are really busy, so sex needs to be more targeted

  • Your partner is away a lot, so having sex requires more planning

  • You want to feel more in control of when you have sex for baby-making purposes


Different brands work in different ways, so whichever you buy, make sure you read the instructions before using them. I tried out Clearblue Advanced Digital (10 tests). Why? As it picks up both oestrogen and LH, typically identifying four or more fertile days, providing me with more advanced warning before I ovulated and therefore, more opportunity to have targeted sex within the days when I was most fertile.

The instructions within the packaging indicated when I should start testing. All I needed to know was how long my cycle is. For me, this is 31 days, so I started to test on day 11. If your cycle length varies, it advises to use the shortest cycle over the last six to work out when to start testing. If you don't know how long your cycle is, it advises to wait at least one cycle and to note down the length, so you know when to start testing the following cycle.

To use the test, I took the cap off the test stick, which I inserted into an electronic holder. I then held the absorbent tip pointing downwards in my urine stream for three seconds, replaced the cap, and waited five minutes for the results to show. A round circle indicated 'Low Fertility' (small chance of getting pregnant), a flashing smiley face indicated 'High Fertility' (a rise in oestrogen and increased chance of getting pregnant) and a non-flashing smiley face indicated 'Peak Fertility' (a surge in LH and the highest chance of getting pregnant). 

The instructions noted to only test once a day using first morning urine until I saw 'High Fertility', then I could test more often to catch the LH surge. They also noted to drink normally (easy enough), but not to urinate for four hours before testing again (little bit trickier – how is anyone supposed to hold on that long!). The idea, is that you have sex the days it shows 'High Fertility', the day it shows 'Peak Fertility' as well as the day after, to increase your chances of conceiving.

Take note that you may not catch the surge in LH though and if you do, it doesn't tell you when the LH surge began. This is why it's important to have sex in the days leading up to when you think you're going to ovulate ('High Fertility' days), to maximise your chances of conceiving and to also prevent DNA damage to the sperm, which can be caused as a result of sperm being stored in the testis for too long. Although it was easy to use, it was really expensive at £24.99. Just to note I'm not paid to promote their product. There are much cheaper alternatives out there, it's just about finding what works for you.


Using ovulation predictor kits are great to give you an idea of when you’re about to ovulate, however, they do have a side-effect that aren't listed on the instructions. For some couples, they can cause unnecessary pressure, which can affect both parties’ ability to have sex, which then leads to added stress, as they worry they might miss their opportunity that month. It’s extremely common and is why some women choose not to use them at all, whilst others choose to use them, but not tell their partners when they get the green light. If you have sex within and around your fertile window, instead of just when you’re about to ovulate, it can help to reduce both you and your partners stress, whilst increase your chances of conceiving. Remember sperm can survive for up to five days in the right conditions. Think of the days before as an insurance policy, encase for whatever reason, you miss the opportunity to have sex on the day you ovulate.


Ovulation tests may not be suitable if you’ve recently been pregnant, have Polycystic Ovarian Syndrome (PCOS), have impaired liver or kidney function or are taking certain medications/fertility drugs. Always read the manufacture's instructions before purchasing.

Juliana Kassianos