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All About Ovulation Predictor Kits

How Ovulation Predictor Kits Help You Detect Ovulation and Get Pregnant


Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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Ovulation predictor kits, sometimes also called OPKs, or simply ovulation tests, come with a set of test strips or sticks that help you time sex for pregnancy. When you get a positive result on the test, you are supposed to have sex for the next two or three days.

The test looks a lot like a pregnancy test, and, like a pregnancy test, you dip the test stick in urine or place the test stick in your urine stream. There are a variety of ovulation predictor kits available, Clearblue Easy and First Response being the most popular.

Like pregnancy tests, you can pay relatively little or quite a lot for a set of ovulation tests, depending on how much technology you want. The most expensive variety of ovulation predictors are digital.

The Clearblue Easy Fertility Monitor is one of the more expensive digital tests, while the cheapest ovulation tests are simple strips of paper, found primarily at online specialty stores.

How Do Ovulation Predictor Kits Work?

Ovulation predictor kits work by detecting the levels of LH hormone in your urine. As ovulation approaches, LH spikes. This spike of LH is called the LH surge. About 36 hours after the LH surge, ovulation occurs.

To increase your chances of getting pregnant, you should ideally have sex the two days before ovulation occurs. Since OPKs help detect the LH surge, which occurs 12 to 36 hours before ovulation, you can be sure to have sex at just the right time for conception.

The Clearblue Easy Fertility Monitor detects LH and estrogen. Because estrogen begins to rise before the LH surge, the Clearblue Easy Fertility Monitor can give you more warning that ovulation is coming, allowing you to have conception sex for up to a week before you ovulate.

How Do You Use an Ovulation Predictor Kit?

Be sure to read the instructions of your particular ovulation predictor kit, since there may be slight variations on how they work.

Generally, however, an ovulation predictor kit comes with a set of test strips or sticks. Some OPKs come with five tests, others with as many as ten. You should begin using the tests about two days before you expect to ovulate. If you’re not sure when you ovulate, you can use an ovulation calculator.

If your cycles are irregular, you should test according to the earliest and latest dates you’d expect to ovulate.

Ovulation predictor kits have two lines. One line is the control, and just lets you know that the test was used properly and is working. The second line is the test line. When the test line is as dark or darker than the control line, LH is surging. This is when you should start having baby-making sex.

If you test for five days, you have an 80% chance of predicting ovulation. If you test for ten days, you have a 95% chance of predicting ovulation.

Clearblue Easy Fertility Monitor works differently from regular ovulation predictor kits, and you need to start testing on the first day of your period. Be sure to read the instructions carefully for the best results.

What Are the Advantages of Using Ovulation Predictor Kits?

Ovulation predictor kits are relatively easy to use. Unlike charting your body basal temperature, you don’t have to remember to have a thermometer right by your bed, or go crazy trying not to move too much when you wake up, so not to ruin the results.

Another advance of OPKs over BBT charting is that they tell you when ovulation is coming, not that ovulation has already passed. Unless you are also checking your cervical mucus, a BBT chart can’t tell you when you should have sex. It can only tell you after it’s too late.

Also, OPKs don’t need to be used right when you get up. While morning urine is best, as long as you take the test within the same six hour window every day, you should be able to get accurate results.

Also, if you're not comfortable checking for cervical mucus, you may feel better using OPKS.

Reading a positive OPK is also easier than trying to read a positive result on a saliva ferning test.

What Are the Disadvantages of Using Ovulation Predictor Kits?

Using an ovulation predictor kit month after month can get expensive, especially if your cycles are irregular and you need to use more than five test strips.

Some people have trouble reading a positive OPK result. If you don’t get a very strong LH surge, you can drive yourself crazy wondering whether or not the test line is as dark as the control line or not. If this is your situation, a digital test may be better, but that means even more expense.

OPKs may not work well for those with PCOS. Women with PCOS may have several LH surges or high levels LH throughout their cycles. Since the OPKs test for LH, they may get positive results all the time or on several days, which won’t help predict ovulation.

Ovulation predictor kits help you detect the LH surge, which signals that your body attempted to ovulate, but they cannot confirm that ovulation happened. It is possible for LH to surge and an egg to never release.

While ovulation predictor kits cannot confirm that ovulation actually took place, body basal temperature charting can. Ovulation predictor kits can be used alongside other methods of ovulation detecting, like BBT charting. This can give you more assurance and help you get to know your body better.

You may want to use an ovulation predictor kit when you just start fertility charting for added confidence. Once you get the hang of charting your BBT and cervical mucus, you can drop the expensive OPKs.

For women who find fertility charting stressful, though, ovulation predictor kits can be a great way to predict ovulation and time sex for pregnancy.

More on getting pregnant:

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Ovulation Kits and Fertility Monitors. American Pregnancy Association. Accessed on February 14, 2011. http://www.americanpregnancy.org/gettingpregnant/ovulationkits.html

Patient Fact Sheet: Ovulation Detection. American Society of Reproductive Medicine. Accessed on February 14, 2011. http://www.asrm.org/uploadedFiles/ASRM_Content/Resources/Patient_Resources/Fact_Sheets_and_Info_Booklets/ovulation_detection.pdf

  1. About.com
  2. Health
  3. Fertility
  4. Ovulation, Sex for Pregnancy, and Reproduction Basics
  5. All About Ovulation Signs and Detecting Ovulation
  6. All About Ovulation Predictor Kits

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