Understanding Ovulation Test Strips & How They Predict Fertility

by Feb 17, 2021

Ovulation test strips, urine based hormone tests usually done at home, are a key tool in any fertility journey. When trying to conceive, pinpointing your fertile window is of the utmost importance. Ovulation is short and knowing your window can give you the best chance to conceive.

Ovulation test

While there are many ways to calculate and track your fertile window, ovulation tests help you maximize your likelihood of becoming pregnant by detecting hormone surges related to ovulation indicating when you’re most fertile. Knowing your fertile window means you’ll know when intercourse is most likely to result in a pregnancy.

If you’re looking to maximize the likelihood of becoming pregnant, tests like these can help you take control of your fertility.    

How do ovulation tests work? 

By now, we’re all familiar with the pee-on-a-stick pregnancy tests found on the market today.    Ovulation tests are similar in design but are used to indicate your fertile window, rather than whether you are pregnant or not.  

But are they reliable?

While pregnancy tests detect human chorionic gonadotropin (hCG) levels in your urine, ovulation test strips work by detecting luteinizing hormone (LH). LH levels remain steady during your menstrual cycle except for a surge that happens just before ovulation.  Ovulation tests detect this surge to tell you when you’re in your fertile window and therefore when you’re most likely to conceive.  

If you’re trying to get pregnant, intercourse at the right time is essential. Your fertile window includes the 4-5 days leading up to ovulation until 24 hours after is the time in your cycle when you are most likely to get pregnant.  Ovulation test strips help you time your fertile window effectively giving you a greater shot at conceiving successfully.  Keep in mind they may not work for everyone, aren’t a guarantee you’ll get pregnant, and are only one tool available on your fertility journey.  

What are ovulation test strips and how do they work? 

Ovulation test strips and ovulation predictor kits are at-home tests used to measure the hormones that indicate ovulation. You can use these tests to determine when you are ovulating and time intercourse accordingly for your best chance of success.  

They come in two forms: threshold-based and semi-quantitative. Threshold-based tests give a positive or negative result based on whether you are above or below a certain level of LH (based on a standard level). Semi-quantitative tests measure LH levels in a way that signifies whether you are low, high, or peak.

Some ovulation predictor kits also measure estrogen, typically detectable a few days before LH surges, giving you even more information to confirm your fertile window.  Tests like these can be especially helpful if your health deviates in any way from population averages.   

Test strip pros and cons

On one hand, test strips are fairly easy to use and are done in the privacy of your own home. But on the other hand, they aren’t foolproof and if not used correctly they won’t necessarily help you. There are both pros and cons to ovulation test strips and fertility strips and they all carry different levels of importance for each person:


  • Women find them easier to use than methods like the basal body temperature method (BBT) because you don’t have to remember to keep a thermometer by your bed or worry about night waking affecting results.     
  • Test strips are more effective than BBT in detecting ovulation as BBT only confirms ovulation rather than predicts it.
  • Kits and strips are widely available online or over the counter at drugstores, pharmacies, and some major supermarkets, without a prescription.
  • More comfortable for some women than tests like checking for cervical mucus to detect changes in ovulation.
  • Ovulation test strips are more convenient than other methods since they don’t need to be used right when you get up and are easy to use.


  • Tests can give false results, either a false positive or a false negative, especially if your LH levels vary from cycle to cycle.  
  • Some women have trouble reading the results and find the second line difficult to interpret.  Is it dark enough for a positive result? This can be difficult particularly if you don’t get a very strong LH surge and the line is weak to begin with.  
  • OPKs rarely work for women with polycystic ovarian syndrome (PCOS) and other cycle irregularities.  
  • It’s possible for LH to surge and an egg to never release, so they can’t actually confirm that ovulation has happened.
  • Using ovulation test strips month after month, if you are having trouble conceiving or your cycles are irregular, can become expensive.  
  • OPKs do not work reliably when certain fertility drugs are present in the system.  For example, injectable fertility drugs like Pergonal or hCG can severely limit their reliability.  
  • Fertility strips may not work consistently on women over 40 due to changes in LH levels.  In their 40s, some women have increased levels of LH in their systems at all times, making any results from ovulation test strips invalid.  

OPK vs ovulation test strips

Ovulation predictor kit, or OPK, and the term ovulation test strip are used interchangeably when it comes to talking about fertility test strips. OPK test strips, also known as ovulation test strips and fertility strips, all work the same way.

No matter what terminology you use, they work by detecting levels of LH hormone in your urine. A spike in LH, also known as an LH surge, indicates that ovulation is on the horizon and now is the best time to have intercourse.  

How to use ovulation test strips

Ovulation test strips either inserted into the urine stream or in a cup of urine you have collected. The strips have two lines including a control line to let you know the test was used properly, and a second line to indicate the results of the test.

When first inserted into the urine, the control line should appear. If this line does not appear you should use a new strip. A second line, usually darker than the control line, appears when LH exceeds a certain threshold. If no second line appears it means you are either outside of the window or LH is too low to suggest ovulation.  

There are always low levels of LH in your body so a lighter or faint line just means you’re not ovulating yet. Using OPK test strips for several days before ovulation should show progressively darker test lines as your LH levels are on the rise and you approach ovulation.

How to read the results from ovulation test strips

You can read OPK test strips by the number and color of lines that appear on the test wand. Reading the results should be fairly simple if you followed the instructions of your particular kit carefully.

Ovulation test strips that are positive will show a second line that is the same in color, or darker than the control line. A negative result will either show no test line, or the test line will appear fainter than the control line.  If no control line appears, consider the test invalid and use a new testing wand.  

Predicting ovulation

Used correctly, most ovulation test strips are effective in detecting an LH surge, a sign that you are about to ovulate. If you start taking tests a few days prior to your anticipated ovulation, you can use the results to predict ovulation. As the LH surges, you should be able to see the result lines get progressively darker.  

Predicting fertility

Ovulation strips can be an excellent tool to let you know when you are most fertile. Studies suggest they can detect ovulation up to 97 percent of the time and can help predict when you’re most likely to be fertile. Your most fertile days of the month are the 1-2 days before and after an egg is released from your ovaries. Start testing ovulation a few days before you are scheduled to ovulate, and you can use the results to predict your fertile window.   

Predicting pregnancy

Using ovulation test strips doesn’t guarantee you’ll become pregnant, but they do play an important role in determining the time you are most likely to conceive.  Your best chance at becoming pregnant involves having intercourse during your fertile window, but by the time you see an LH surge, you are already in the middle of your window.

Use ovulation test strips before you are scheduled to ovulate to see how your levels of LH rise. This helps you know when you should have sex to get pregnant.  

How accurate are ovulation test strips?

Used correctly, these tests are over 97 percent effective in detecting an LH surge. Because an LH surge is a surefire marker of ovulation for most women, using test strips to monitor the process is more precise than other methods. You can increase the effectiveness by combining them with other methods.

How much should you expect to pay?

Prices for ovulation test strips and ovulation predictor kits vary greatly based on factors like quantity, brand, and design. A basic box of strips will cost anywhere from $12 to $25 with most brands offering similar reliability. Digital readers cost slightly more, anywhere between $30-$50, but may be available for reimbursement through your healthcare insurance.

A digital fertility tracker, like Mira Fertility Analyzer, will have a higher initial investment than basic strips, but offers more personalized information such as hormone concentration in your urine, similar to results you would get at a doctor’s office. This information can then be used to track your cycle over time via the app to help you pinpoint your most fertile days.  

Ovulation test strips are an easy and accurate tool to help you pinpoint your LH surge and predict ovulation. While they are convenient for some, they may not be right for all women and you can talk with your doctor or healthcare provider to find the best option for you. Use ovulation test strips to time your best opportunity to conceive and increase your chances of getting pregnant.

Written by Fertility Nutrition Hub

Order Your Mira Plus Today

Track your whole cycle and what is happening with your hormones. Get a larger fertile window (6 days) and clear insights. Let Mira take the guesswork out of tracking all fertile days and infertile days.