How to use ovulation test kits

Most women don’t give much thought to when they’re ovulating before they’re actively trying for a baby. But if you’re trying to conceive, knowing when you ovulate can be a clue to knowing your fertile window. Find out what ovulation is and how to pinpoint when you’re ovulating using an ovulation test kit.

What is ovulation?

Ovulation is the process that results in the release of one or more eggs from your ovary. Each month, between three and 30 eggs mature inside one of your ovaries (Knudtson and McLaughlin 2019). The largest is pushed out into the pelvic cavity and swept into the fallopian tube.

Your egg survives for between 12 and 24 hours if it’s not fertilised (NHS 2018). There’s a small window each month during which you can conceive, usually around six days. This time leading up to ovulation is your most fertile time (your fertile window).

How do ovulation tests work?

Urine-based OPKs test your wee (urine) for an increase (surge) in luteinising hormone (LH). This starts one day to two days before ovulation, with levels of LH peaking about 12 hours before the egg is released (Reed and Carr 2018).

A small amount of LH is always present in wee. But during the surge the amount of LH increases by about two to five times, which triggers ovulation (Payne 2018, Reed and Carr 2018). The days leading up to and including ovulation are the most fertile part of your cycle. This is when you are most likely to conceive.

Some urine tests also test for a second hormone, called estrone-3-glucuronide (E3G) (Tommy’s 2019). This hormone is produced when estrogen breaks down in your body and is present in your wee around the time you ovulate (Tommy’s 2019).

Salivary ferning kits allow you to test your saliva with a pocket-sized portable microscope. As your oestrogen levels rise, the salt content of your saliva increases. When the salt dries, it crystallises into a fern-like pattern (Payne 2018).

In the two to three days leading up to ovulation, and for a couple of days afterwards, salivary ferning is visible, so checking for this helps to identify your fertile window. When you are not in your fertile window, your saliva will dry in shapeless blobs (Payne 2018).

Can ovulation predictor kits help me get pregnant?

An ovulation predictor kit (OPK, also known as an ovulation test) is a quick, easy, and accurate way to predict ovulation in advance. It allows you to pinpoint your fertile window from the very first month. Kits are available online, and at most chemists and supermarkets. You can usually find them in the same section as pregnancy tests.

However, there is no evidence that ovulation testing using an OPK will improve your chances of getting pregnant naturally (NICE 2019).

It’s possible for sperm to survive inside you for up to seven days (FPA 2018). This is why experts say that having sex every two or three days throughout your cycle, instead of just around ovulation, will give your egg the best chance of being fertilised by a healthy sperm (FPA 2018, NICE 2019).

You may prefer to schedule sex for your fertile period if:

• You, or your partner, work away from home a lot, which makes regular sex difficult.
• You and your partner have hectic schedules and already have children. Sex may not be a priority, and having sex every two days to three days may feel like just another chore.
• You have an irregular cycle, which makes it more difficult to conceive.

There are a few other ways to determine your fertile window. You could record your menstrual cycle, chart the monthly cycles of your basal body temperature, or study changes in your cervical mucus. Or you could try all three.

Our ovulation calculator can also help you to work out your fertile window, as long as you know the date of the first day of your last period and the average length of your menstrual cycle.

However, if your menstrual cycles are irregular, it can be tricky to pinpoint ovulation. This is where ovulation predictor kits (OPKs) can help.

How do I use an ovulation kit?

With either type of OPK, it helps to have a rough idea of when you may be likely to ovulate, because you’ll need to start using the test several days before this.

Ovulation usually happens about 10 to 16 days before your next period starts (FPA 2018, NHS 2019). So, for example, if you have a 28-day cycle, this will be about day 14. If you have a 35-day cycle, it will be about day 21. Use our ovulation calculator to help you work out when you’re likely to ovulate.

Start using the OPK three to five days before you’re likely to ovulate, or when the instructions advise you to. Carry on testing for six days, or as long as the instructions say.

If you have an irregular cycle, keep an eye on your cervical mucus. When you start to notice more slippery discharge that looks a bit like egg white, ovulation may be on its way. This is a good time to start using an OPK to find out for sure.

Urine-based OPKs

With urine-based OPKs, you’ll either collect your wee in a cup or hold a stick under you as you wee. Coloured bands will appear on the test card or stick to indicate whether or not the LH surge is occurring. Digital OPKs use symbols, such as a smiley face, to tell you when you are on your most fertile days.

Make sure to follow the instructions of the kit you’re using, telling you what time of day to take the test. Some brands require you to test your first wee of the day, while others recommend late morning to early afternoon testing.
Try to reduce the amount of liquids you drink for about four hours before you do the test. Too much liquid will dilute your wee, which could make it more difficult to detect the LH surge (Jacobson 2019).

Read the results within 10 minutes. A positive result will not disappear, but some negative results may later display a faint second colour band. So throw the test card away once you’ve read the result.

Salivary ferning OPKs

Using a salivary ferning OPK is perhaps easier, as all you have to do is place some of your saliva on a slide by using your finger or a stick provided with the kit, or by licking the slide. Do this first thing in the morning, before you’ve had anything to eat or drink. Make sure you don’t put too much on and that it is free of any air bubbles.

You then wait for the saliva to dry and then use the microscope to see whether there is any ferning or not. Compare your slide with examples in the instructions to see whether you’re in your fertile window.

What else do I need to know about ovulation kits?

Paracetamol and other common drugs don’t affect the tests. However drugs containing human chorionic gonadotrophin (hCG) or LH can affect the test results, and the fertility drug Clomid can also affect the results (Jacobson 2019).

When used correctly, urine-based LH tests will reliably detect the LH surge before ovulation about nine times out of ten (FDA 2018a). However, they're not foolproof and will also pick up any LH changes that are not linked to ovulation.

Salivary ferning tests aren’t as accurate as LH tests (Payne 2018). Ferning can happen at other times in your menstrual cycle, or if you are pregnant (FDA 2018b). It may also be hard to judge if ferning has happened or not – if you have poor eyesight, salivary ferning kits may not be the best method for you.

How much do ovulation kits cost?

Standard urine-based OPKs cost from a few pounds per cycle up to over £10 per cycle. Most brands offer the same level of reliability, so pick the one that offers you the most tests for the least amount of money.

All kits come with a list of frequently asked questions about performing the test. Once you use the test and detect your surge you can stop testing for that cycle. You can then save any unused tests for the following month (unless you conceive, of course!).

Salivary ferning OPKs can be better value. After the initial outlay of about £20 to £50 for the microscope, you should be able to use it again and again. However, if it takes you a long time to conceive, depending on the brand, you may have to replace it after about two years if it becomes worn.

For a little extra money, some OPKs include a digital monitor to record your results over several months. Alternatively, you could try downloading one of a number of free apps that allow you to add your personal information from test results, alongside tracking your cycle (Tommy’s 2019).

Find out exactly what happens when you ovulate and discover the best sex positions for getting pregnant.

• Get help to pinpoint your ovulation using our ovulation calculator, all you need is the date of your last period and your cycle length.
• Keep track of your basal body temperature and cervical mucus.

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