What are LH tests, ovulation tests and ovulation prediction kits (OPKs) and how to use them.

What is an ovulation test AKA LH test/OPK?

An ovulation test works by detecting the surge in the hormone luteinizing hormone (LH) which peaks just before ovulation. They work in a similar way to pregnancy tests but instead of peeing on the test, you pee into a container and dip the stick into it. You need to hold it in the urine for a specific amount of time (see instructions as the time for each brand will vary). Then you wait for 5 to 10 minutes for the test results to develop.

Do ovulation tests work?

Yes they really do and without using OPKs I would never of conceived my son. Some women are lucky enough to ovulate at the same time every cycle and I envy them so much. Trying to get pregnant when you have irregular and long cycles like mine is very difficult. This is why I have dedicated a section to ovulation tests as they can be extremely useful and will save a lot of guess work. I will take you through how to use them most effectively and the most common mistakes woman make when using them. I will also give suggestions of the best ones to buy and answer the common question of whether OPKs can be used as pregnancy tests. I will also give you a quick review of the Clearblue ovulation monitor which I tried and tested.

When is the best time to take an ovulation test?

The hormone you are testing for when using ovulation tests or OPKs is luitinizing hormone (LH) which is the hormone that peaks just before ovulation. The peak in LH may only last a short amount of time so it is important that we catch that surge and get our positive test. When I first started using OPKs I would test in the morning which is what the instructions said to do. My cycles were quite long and I became a bit obsessed about missing my LH surge so I bought a bundle of cheap LH tests and started peeing on them every morning and evening from cycle day 10. Every cycle  the OPKs would be negative in the morning and positive in the evening the day before I ovulated. It seemed that for me they worked better in the evening. I would not drink anything from around 4pm and hold my urine for 2-3 hours so it was nice and concentrated and then do the test around 6-7pm. I caught my surge every cycle. I have friends who told me that OPKs never worked for them so I suggested using them in the evening and it seemed to work for them too. It turns out that our levels of LH increase throughout the day from morning to evening so this method makes sense.

How long after the LH surge does ovulation occur?

This depends on the individual a woman usually ovulates 12 to 24 hours after LH has has reached its threshold level.

How long do ovulation tests stay positive?

I found that for me, ovulation tests stay positive for up to 24 hours but the surge can last a varying degree of time  depending on the individual. It can last just a few hours and for those women that this happens to, OPKs may not work for them if the test at the wrong time.

When does ovulation occur after a positive OPK?

If you get a positive OPK i.e. the test line is as dark or darker than the control line, then it is a very good indication that you are about to release your egg within the next 12 to 24hrs.

How to read an ovulation test?

It was always very confusing to me when using OPKS that I would get a faint line on a ovulation test throughout the follicular phase before I ovulated. I would always get excited when I would see a second test line appear, especially when it was quite dark and I would think I was going to ovulate the next day but didn’t. The next day the tests would be negative again and I knew from my temperature chart that I hadn’t ovulated so it was very frustrating. If I wasn’t taking my temperature every day and monitoring my other fertile signs I would of believed I had ovulated when I hadn’t and would probably miss the chance of conceiving that cycle. After a bit of reading I found that we actually have LH in our systems all the time at low levels but they can fluctuate throughout your cycle. So unlike pregnancy tests you will have a second line on your test almost every time you take one. Below is an example of an LH test strip or OPK taken on day 10 of my cycle. As you can see there is a second line but it is faint compared to the control line. I didn’t ovulate for another 10 days or so.

Are ovulation tests accurate?

Yes they are. The key is for the second line or line furthest from the green/blue part (i.e. the test line) to be as dark as or ideally darker than the control line on the ovulation test and for all your other fertile signs to be in place e.g. watery/egg white cervical mucus (more on that here). Below is an example of a positive cheap ovulation test which I took a few months back. I ovulated the next day and got my temperature rise the day after.

Is there such a thing as a false positive ovulation test?

The answer to this depends on the individual and the type of ovulation test they are using. If you use the cheap ovulation test strips then it is down to the individuals’ interpretation on whether the test line is as dark or darker than the control line. If you see a dark line and you have your other fertile signs and you know you ovulate regularly then it is more than likely that a dark test line means you have a surge in LH and will ovulate soon after. With the digital tests you will see either an empty circle or smiley face so you don’t need to decide for yourself. Of course, just because you see a positive ovulation test does not mean you will definitely ovulate afterwards. This can happen with anovulatory cycles where the LH surge may occur (and you get a positive OPK) but it doesn’t reach the threshold level needed to stimulate the release of the egg so you do not ovulate. Instead, you get your period a few days later (more on this in the Fertility problem section). This is why it is very important if you do not know that you are definitely ovulating to start charting your temperatures. If you get a positive test but no sustained rise in your body temperature then it was a false positive.

What is the best ovulation predictor kit?

I have tried several different brands of ovulation tests but I found that some were 5 times more expensive than others and worked in the same way. I started out using the Clearblue ovulation tests and although they work great and I found them to be very reliable they are very expensive. You can however buy them cheaper online than from the high street – see Amazon’s price for  7 tests here.

Due to my long cycles and because I was a pee on a stick addict and I wanted to test every day from day 10 of my cycle, I soon realised after several months that the costs were adding up. I would often ovulate as late as cycle day 35 so it just wasn’t feasible for me to use them daily. I then tried the cheap ‘Ovulation test strips‘ you can get online and  I found that they work just as well. They just don’t have the fancy packaging. They come in two sensitivities, 20miu and 10miu, and I found the more sensitive 10miu to work better for me. You can buy 50 10miu ovulation tests on Amazon for less than £7 (see below). Although it is much easier to see a smiley face like on the Clearblue digital ovulation tests, the cheap ovulation strips do work really well and you will save yourself a ton of money if you have been trying for a long time.  You can use one everyday up to ovulation without worrying about cost.


Buy ultra sensitive ovulation tests (10miu).


What if you get egg white cervical mucus but a negative OPK?

This is asked a lot on trying to conceive forums. Lots of ladies get the fertile egg white cervical mucus each cycle but OPKs don’t seem to work for them. This is quite common and the first thing I would say is to change to the more sensitive test i.e. from 20miu to 10miu. The picture below is posted here again to show you why. You can buy ovulation test strips 10miu here.


The top test I would say is negative but the bottom one is positive. Tested with the same urine, the different sensitivities give differing results. With the 10miu tests you are more likely to get a positive test when you are ovulating and there is less guess work when analysing the results.


How to use an ovulation test strip kit? Step by step guide.

The video below is a demo on how to use the ovulation test strips and also shows you what a positive test looks like when it is developing.

The test finished developing after a few minutes and the test line was as dark as the control line (see below) giving a positive result.

Why do I never get a positive ovulation test?

Some women only get a surge in LH for a short time (6-12 hours) before it disappeared from their system. If you are consistently getting negative OPKs each cycle then it is worth testing twice a day as you may be missing it. Once around midday and once in the evening from 7pm on wards will double your chances of catching the surge. If you still are not getting a positive OPK then I suggest you start charting your ovulation if you are not already, to confirm you are actually ovulating each cycle. The odd anovulatory cycle is quite common but if you are not ovulating on a regular basis it is time to see your GP. In the mean time, you can have a look in the Fertility Vitamins and Fertility Herbs section for natural ways to stimulate ovulation (soy Isoflavones in particular may be helpful).

Can you use an OPK as a pregnancy test?

The pregnancy hormone (HCG) and luteinising hormone that the OPKs pick up have an almost identical structure. OPKs cannot distinguish between the two hormones so can in theory pick up the pregnancy hormone in your pee. So can ovulation tests detect pregnancy? This is a question that is often asked on trying to conceive forums as women have missed their period and they haven’t’t got a pregnancy test at hand, so pee on an OPK. They get a second line on the ovulation test and then wonder whether they could be pregnant. I tried this when I was pregnant with my daughter and I can confirm that they do pick up the pregnancy hormone however they shouldn’t be relied upon. I got pregnant with my daughter when living in Gran Canaria and you can only buy pregnancy tests in pharmacies there. You can’t buy them in supermarkets or in your local Boots store. They were 10 euros each so I couldn’t afford to buy a lot of them even though I wanted to test every day for the first few weeks of my pregnancy. I was super paranoid about having a miscarriage (having had two in the past). I used up all my pregnancy tests so began peeing on the cheap OPKs I had lying around. I can confirm they got darker and darker each day and soon reached as dark as they could possibly get when I was around 6-7 weeks pregnant (see below).

Although I can confirm they do pick up the pregnancy hormone I would say they are not a reliable indicator that you are pregnant before you have missed your period or within the first few weeks or so after you have missed your period. This is because (as stated above) you always have LH in your system so you will always see a second line on the test so you will always have doubt in your mind. Pregnancy tests are more reliable as you will only see a second line if you have the pregnancy hormone as they can distinguish between the two hormones. OPKs can work well as pregnancy tests if you are further along but not at the beginning.

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