How to Choose The Best Ovulation Predictor Kits

Everyone is familiar with pregnancy tests, but how many of us knew about ovulation predictor kits (OPKs) before we started trying to have a baby? Ovulation predictor kits are amazing tools in our fertility toolbox. They can help us time baby making, but OPKs are essentially useless without understanding how to use them properly.

How Do Ovulation Predictor Kits Work?

Ovulation Predictor kits work by measuring the LH hormone in your urine. The LH hormone rises to initiate ovulation. The ovulation predictor kit works by detecting this rise in LH hormone. Below is an example of an LH curve. You can see that ovulation occurs when the LH level spikes. This rise in LH will trigger your OPK to turn positive.

ovulation curve

Best Ovulation Predictor Kits

Digital Ovulation Tests

These are the OPKs you may confuse with pregnancy tests. With these you pee on a stick and it gives you a + or ☺ to signal that ovulation will occur in the next 24-36 hours. I recommend the Clearblue Digital Ovulation Test. It is the easy to use, accurate and reasonably priced.


  • Easy to Use: Pee on a stick
  • Easy to Understand


  • Expensive

Ovulation Strips

These are plastic strips you dip into a cup of urine to test the LH level. Ovulation strips work a lot like pregnancy tests in that when ovulation is approaching you should see two lines. The first line is the test line and the second line is the control. The test isn’t positive until the test line is as dark or darker than the control line. I recommend the Pregmate LH Test Strips. They are easy to use, accurate and a good value.


  • Good Value
  • Able to test often


  • Difficult to interpret
  • Difficult to use

When to Test

Now that you have purchased your ovulation predictor kits you need to know how and when to use them. This depends on the length of your menstrual cycle as well as the regularity. If you have a regular menstrual cycle:

Subtract 16 days from the first day of your period and begin testing on that day.

For example, if you cycle is 28 days you should start testing on day 12. If you cycle is very irregular I would recommend buying the strips and begin testing earlier and continue testing until you see a positive or until your period begins. The strips are relatively inexpensive so if you are nervous there is no harm testing for a longer period of time. If you have a regular cycle and your ovulation is consistent, you could get the digital OPKs and test for less days.

The best time of day for ovulation testing is in the afternoon. This is when you are most likely to get a positive result.

Once you have a positive you can stop testing or you can continue until you have a negative. This may provide reassurance that your LH spiked, you ovulated and then your LH went down.

What To Do When You Get a + Result

Hurray! Your test came back positive! This means you should ovulate in the next 24-36 hours. Have sex that day and the next 2 days. Remember, your egg can be fertilized for up to 24 hours after ovulation. So if you don’t ovulate until 36 hours after your test, you may still be fertile in that third day.

What if You are Doing it All Right and Still Not Getting Pregnant

If you are consistently using ovulation predictor kits, getting a positive result and still not becoming pregnant it could be that you are not ovulating despite a rise in LH.

The only way for you to know you are ovulating at home is to chart your temperatures.

You can find out how in my article on the Fertility Awareness Method. In this method you are looking for a temperature spike. This temperature spike happens after ovulation has occurred. If you rely solely on temperature charting you will miss fertile days before ovulation occurs. Charting can assure you that ovulation has occurred.

If you are measuring basal body temperatures make sure you are checking them at the same time every day before getting out of bed. If you are getting positive results on your OPKs and you are seeing a temperature rise through basal temperature charting, it could be an issue with implantation or with your partner’s sperm.

At this point you want to see a fertility specialist who can order a semen analysis for your partner and can order blood work and an ultrasound to evaluate other causes of issues.