Are ovulation predictor kits or basal body temperature a better indicator of ovulation?

Varvara February 02 2022

You probably know at least one woman who regularly uses ovulation predictor kits in order to help her conceive. But did you know that basal body temperature can be an even more accurate way of determining when she's going to release that egg?

If you're considering using either or both methods, it's important to understand their benefits and limitations.

Ovulation Predictor Kits

What is Ovulation Predictor Kits?

An ovulation predictor kit ("OPK" for short) is a collection of tests that a woman can take in order to predict when she's going to ovulate. She takes the test each day and looks for two lines appearing on the indicator strip - this would indicate that estrogen levels are present, which means that ovulation will occur within the next 12-36 hours.

The ovulation predictor kit tests the urine for luteinizing hormone (LH) which increases prior to ovulation. The LH surge precedes rupture of ovarian follicles, which results in the release of an egg. By identifying this LH surge, you can predict when you are going to ovulate within a 12-36 hours time period.

It's also possible to determine your daily fertility status by looking at these two lines - if the test line matches or is darker than the control line, then it means that ovulation will occur within 24-48 hours. If the test line is lighter than the control line, then you are not yet fertile and should continue testing until your fertile window begins. If there is no test line at all, then you are probably not ovulating during that cycle. You will need to test again the following day, starting with a new kit.

Why Use Ovulation Predictor Kit?

There are many reasons why women choose to use an ovulation predictor kit. Perhaps you're trying to get pregnant and want to know when you're most fertile so that you can have sexual intercourse at the right times. Or perhaps your periods are irregular for some reason (you may be approaching menopause or breastfeeding, for example), and you've heard that using an ovulation predictor kit can help determine when your next period will occur.


  • They are easy to use: you basically pee on a stick and wait to see what happens.
  • They are relatively inexpensive: a box of 20 sticks typically costs less than $20.
  • You can test every day if you want. This is especially useful if your cycles vary greatly in length each month, or if you're trying to get pregnant and want to know as soon as possible when the best times to conceive would be.
  • The results are highly accurate (when used correctly). If you do not see any lines on the test strip, this means that ovulation will not occur within the next 24 hours - but it's possible that ovulation will still happen at some point within the following 48 hours. Please note that although these kits can provide very accurate results, they should never replace regular visits to your doctor or discussions with your healthcare provider.


  • They are not always accurate. This is because the LH surge does not occur in all women - it may be that you don't have a large enough surge, or perhaps it's just too difficult to detect for some reason.
  • They are less accurate if your cycle varies greatly from one month to another, or if you tend to have very irregular periods. This is because ovulation predictor kits test only for the LH surge, which means they can't accurately predict when you will release an egg in cases where no clear LH surge is detected.
  • They do not work for everyone: some women swear by them while others claim they are completely useless. It may be that you're experiencing issues with fertility (or it could even be genetics), and your body releases too little LH for the kits to detect.
  • They may be expensive over time: if you're using them every day (which some women do in cases where they are trying to get pregnant), then this could add up quickly.
  • You need to make sure you follow instructions carefully: you will see two lines on the test strip, but not all of them will indicate that ovulation is about to occur within 12-36 hours - only the one that is darker than the control line means that ovulation is impending. If no clear lines appear at all, then it either means you're not yet fertile or that it's taking longer for your fertility window to appear than usual. In such cases, keep testing each day as indicated.

When should I use the ovulation kit?

The ideal time to use an ovulation predictor kit is when you are about to enter your fertile window. So, for example, if your cycle typically lasts 28 days, then you should begin testing once day 14 has passed. Keep in mind that the length of your menstrual cycle can vary greatly from one month to another - so what may have been day 14 during your last period may be day 21 the next month. In addition, if you're trying to conceive it's important not to test too early as this could lead to false readings and a low level of accuracy.

How do I read the ovulation kits?

These stick ovulation tests are similar to pregnancy tests. They show lines, and one of the darker ones will be an indicator that you'll soon peak reproductive period - when your chances for conception triple! These less expensive alternatives can sometimes take more effort on readability than other types but still provide good information about whether or not there's anything special happening with regards to timing a pregnancy.

Place the stick in your urine stream or collect a sample in a cup and dip it into the test area. - Wait for five minutes to see if two lines appear – one line will be darker than the other, indicating that there's been an LH surge that may lead to ovulation within 12 to 36 hours. No line means that ovulation will not happen within 24 hours at least, so it's time to reschedule those babymaking attempts!

In order for these kits to provide accurate results, they have to be used correctly at the time of day specified by its instructions. If you use them too early or too late, then their accuracy rate goes down significantly as well as being able to predict when you should have intercourse.

Although basal body temperature can also be used to detect ovulation, the ovulation predictor kit is a much more accurate indicator.

Basal Body Temperature

In the past, women would use a basal body temperature thermometer to determine whether they were ovulating or not. You can still do this today if you'd like, but it's a bit more complicated than simply peeing on a stick and seeing what happens. That said, some people find that tracking their BBT chart is even more accurate - particularly for those with very regular menstrual cycles. The reason for this is that your BBT rises slightly after an egg has been released from your ovaries (this is also referred to as ovulation). In cases where there's no rise in temperature following the release of an egg, then it means that either no egg was released during that cycle or there was no ovulation in the cycle at all. In either case, it's a clear sign that you may have fertility issues and should speak with your doctor to discuss the possibility of doing some additional testing.

Conception Control

In order for conception control to be possible through the use of a basal body temperature chart, then it's important that you track your BBT accurately each day at about the same time. This means taking your temperature before getting out of bed in the morning and going back to sleep - not after being up for five minutes or more because this can cause a slight delay in getting an accurate reading if they're taken too soon after waking up. If you make sure to take your temp as closely as possible to when you wake up each morning, then your chart will reveal a pattern that can be used to predict ovulation in advance.

How does the basal body temperature method work?

Once you become pregnant, your BBT stays elevated for the duration of pregnancy - this is how you can tell whether or not you're having a boy or a girl when you get down to two months from your due date. The idea here is that if your BBT remains high enough after ovulation, then chances are good that there's been an egg released during that cycle and it's likely just a matter of waiting until the 18th day of your cycle. If your basal body temperature dips after being elevated for several days, then it could mean that either no egg was released during that cycle or there was no ovulation. If so, then it's a good idea to consider seeing your doctor if you've been trying to conceive for over six months without success.

Does charting BBT help you increase your chances for pregnancy?

If you can take your temperature at the same time each day, then there's a good chance that charting your basal body temperature will increase the chances of a successful conception. That said, this method does have a high failure rate. In fact, only 20%-25% of women who use it for this purpose end up getting pregnant in any given cycle. This is why many women opt to try one or more additional methods along with tracking their BBT in order to boost their chances for success.


  • Can help to determine whether or not you're ovulating on schedule: If your BBT is low after ovulation, then there was likely no egg released during that cycle. If it's high, then chances are very good that you did release an egg and now it's simply a matter of waiting until the 18th day of your cycle before trying to conceive.
  • Provides useful information for women who have irregular cycles: Charting BBT can be done by anyone regardless of how often their menstrual cycle varies from one month to the next. In cases where a woman has an irregular cycle, then being able to predict ovulation in advance can help them avoid getting pregnant when they don't want to or help them prepare when they do want to conceive.
  • Can be done without making any changes to daily routine: You can track your BBT at about the same time each day - before getting out of bed in the morning and going back to sleep. This may require some additional effort on your part, but it's typically not difficult to do.
  • Can be done without making any special purchases: You don't need anything other than a simple thermometer that can provide accurate readings. This is why BBT charting is one of the least expensive methods for conception control available today.


  • Requires consistent scheduling from one month to the next: In order for this method to work as expected, then you must take your temperature consistently at about the same time each day - ideally before getting out of bed in the morning and going back there again. If you're not able to do that, then this method probably isn't going to work for you.
  • Doesn't provide any information about when you should have sex: In other words, there's no way of knowing whether or not you should have sex every day from the time your BBT rises until ovulation occurs or once a week from the time it begins rising until ovulation occurs. This can be a disadvantage for women who don't want to get pregnant and men who want a better idea of when their chances are best.
  • Can take up a lot of time if done correctly: When done right, tracking basal body temperature requires consistent attention to detail. It also requires effort on behalf of both partners in order to overcome any obstacles that might get in the way of having sex as often as possible.
  • Doesn't always work: Less than 20%-25% of women who use this method for conception end up getting pregnant in any given cycle. This is one reason why many women choose to use additional methods along with BBT tracking in an effort to boost their chances for success.

What is the difference between BBT and ovulation predictor kits (OPK)?

Ovulation predictor kits test for the presence of the luteinizing hormone in a woman's urine. This is done by dipping a home ovulation test strip into a cup. Results will be provided within five minutes. They're not perfect, but they do provide an idea of when you should have sex if you want to lower your chances of getting pregnant. Getting pregnant can happen at any point during a menstrual cycle - even after a period ends and before the next one begins. In cases where women have irregular cycles, then knowing when ovulation occurs is very important. That's why many people opt to use OPKs or BBT charting together - one provides more information than the other alone does and neither method is perfect by itself.

So, what is best, BBT or tracking LH levels?

If you have an irregular menstrual cycle, ovulation predictor kits are a better option. If you do not experience changes from month to month with your cycle and can easily identify the time of ovulation during your monthly fertility window, then basal body temperature also does a great job at pinpointing when ovulation occurs. Many women opt to use OPKs or BBT charting together - one provides more information than the other alone does and neither method is perfect by itself.