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How & when do you use an ovulation predictor kit (OPK)? Ovulation predictor kits are great in that they pinpoint exactly when you are ovulating by measuring the luteinizing hormone (LH) in your urine, which is present at the time of ovulation. And as you know, unless you are catching the moment of ovulation (when your egg is released & ready to be fertilized), then you will have a slim chance of falling pregnant.  Claim Your 20 Free Ovulation Tests – Click Here


How do I use an OPK?

An ovulation predictor kit is very similar to a pregnancy test. Just like a pregnancy test, it comes in large midstream applicator size and smaller test strip size. Again, like a home pregnancy test, you simply pee on a stick. One line is just the control line, indicating that you are not ovulating. Two lines indicates that you are about to ovulate. Both sizes function exactly the same, in that they measure the amount of LH in your urine. When an LH surge is detected, you know that you are ready to ovulate in the next 24-48 hours.

When do I Take an Ovulation Test Infographic

TIP #1: So if you get 2 lines, it’s time to grab your man and get busy!


When in my cycle do I take an OPK?

Cycles vary greatly from woman to woman, however the average cycle length is about 28 days with ovulation occurring on cycle day 14. Cycle day 1 is the 1st day of your menstrual cycle. Now if you have a typical by the book 28 day cycle, then you want to start testing using these at about cycle day 11. However if you’re like me then you could ovulate anywhere between cycle day 12 to cycle day 22, so there’s no way that I could survive without my ovulation predictor kits. Here is a chart to help you decide when to best begin testing. It is advisable to be conservative and begin testing earlier than later, so you make sure you don’t miss the big O. So even for a 28 day cycle, you wouldn’t wait until day 14 to test. You would start at about day 10-11.

TIP #2: Begin testing at day 10-11 for a normal 28 day cycle.


What time of the day to use an OPK?

The next question is when during the day do you even use an OPK? It’s not like a pregnancy test where you use your 1st morning urine. You don’t want to do that. Instead you want to test about midday though. And remember, don’t dilute your urine or you will not get accurate results. Therefore, the best time of day to take the test is from 8 am to 10 pm.

TIP #3: The ideal time is to take the OPK in the afternoon.


Why should you not use first morning urine for ovulation test?

It may seem confusing to you that you are able to take pregnancy tests first thing in the morning, but not ovulation tests. The reason for that is because when you are taking a pregnancy test, you are looking for the hormone, hCG, aka the pregnancy hormone. The presence of the hormone is strong first thing in the morning, though you can take it at anytime of the day as well.

However, what the ovulation test detects is the LH surge, and LH is synthesized in your body in the morning. Therefore, it will not appear in your urine until the afternoon, and that is why it is ideal to take the test at that time of day.

TIP #4: Wait until lunchtime or after to test for the LH surge.


Should I take an OPK twice a day?

Ovulation is fleeting. Once you are getting close to ovulation, either noting you are near to the middle of your cycle (roughly day 14), or you have noticed abundant egg-white cervical mucus, it may be wise to test twice a day. You don’t want to miss the surge. Ovulation predictor kits also vary in their line darkness. As you approach ovulation, the test line will start growing darker. So testing twice a day will show you the test line growing darker, to give you a heads-up so you don’t miss the surge.

OPK test results

TIP #5: As you approach ovulation, test twice a day (every 12 hours) so not to miss the surge.


How long after a positive ovulation test do you ovulate?

Like it was mentioned before, once you get a positive on the test due to the LH surge, ovulation can happen anywhere between 12-36 hours. That is why it is important to have intercourse as soon as you see there is a surge.

If you happen to ovulate on the same day that you see the LH surge, especially if you were to test earlier in the day, then you may end up missing the window. Bear in mind that the egg that is released is only viable for 12 to 24 hours. If the egg is fertilized towards the end of its life, it may not stick.

TIP #6: You will ovulate within 12-36 hours of a positive OPK. Get busy now!


When should I have sex after a positive OPK?

As soon as you get a double dark-line on your ovulation test, you know you are about to ovulate. So have sex that day, as well as the next 2 days following to be sure. And then you are bound to catch the egg!

TIP #7 Have sex the same day as a positive OPK, plus 2-3 days following.


How long can you get pregnant after a positive ovulation test?

As noted before, the LH surge appears when you are about to ovulate within 12 to 36 hours, meaning it could happen on the same day. As soon as ovulation happens, that is when pregnancy can occur. That is why it is a great idea to monitor your cervical mucus as well as taking the ovulation test because you will want there to be sperm in your reproductive system even when you have a positive LH surge, since ovulation can literally happen anytime once it is detected.

An eggwhite cervical mucus is an indication of a possible ovulation

If you are not aware of what to look for while analyzing your cervical mucus throughout your cycle, then you need to understand as soon as your mucus is abundant and has a raw egg-white appearance, that is the time to start getting busy, even if the LH surge has not yet been detected on the OPK.

When your cervical mucus has that kind of consistency, as opposed to being scant and dry right after your period, or cloudy and sticky when you are not ovulating yet, ovulation is near.

It is also a good idea to start having intercourse when your cervical mucus starts having that egg-white like consistency. That is because sperm can live in your reproductive system for up to a week, or maybe even longer. This way, when the egg is released, you will have sperm right there waiting to fertilize it right away! Seeing the LH surge on your OPK is confirmation that ovulation is literally right around the corner!

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TIP #8: You can get pregnant up to 36 hours after a positive ovulation test.


Can you get pregnant on the day of ovulation?

Absolutely! Ovulation day is THE time to get pregnant.

But it is not the only time to get pregnant. As soon as you ovulate, and you have sperm in your system that has been “waiting,” then the odds of conception happening are extremely high.

However, if you have not had sex until after you have ovulated, you may not get pregnant depending on how old the egg is, since it was already noted that the egg will no longer be viable after 24 hours, usually within 12 hours it is at its best condition.

That said, if you have had a day to several days intercourse prior to ovulation, then the odds of you getting pregnant on the day of ovulation is extremely high. If you waited until you had already ovulated, then the odds of conceiving drop due to the quality of the egg dropping as the hours are ticking down.


TIP #9: Yes, ovulation day is the best time to get pregnant.

When LH surge is over, have I ovulated?

In most cases the answer is yes you have ovulated after the LH surge has been detected. That means that once your second test line on your ovulation predictor test or test strip starts lessening in color, your LH surge is ending.

luteinized unruptured follicle syndrome

However, once in a while, even after the LH surge, the egg does not always emerge from the follicle which means ovulation did not happen. This condition is called  LUFS (luteinized unruptured follicle syndrome) and it is not very common.

TIP #10: Once your OPK lines are no longer both dark, the LH surge is over and you have ovulated.


How many days are you fertile after LH surge?

There is no set time for how many days you are fertile after the LH surge. Sometimes you are fertile on the day of the LH surge, or up to 36 hours after it has been detected.

Again, this is why it is highly recommended to monitor your cycle by watching the change in consistency of your cervical mucus. As soon as it becomes abundant and has the appearance of raw egg-whites, then you should have intercourse before the surge.

You may be fertile for one day after LH for one cycle, and the next cycle you may be fertile for 2 days after the surge. There is no set time on how many days you are fertile once the surge in LH has been found.

TIP #11: You are fertile up to 12-36 hours – so have sex on the day of the LH surge and positive OPK,  and 2-3 days following


How many days can you detect LH surge?

Again this can vary, LH may be detected for only one day, but it is usually from 2 to 2.5 days. The peak time of the surge may last from 12 to 24 hours once it has been tested positive on the kit.


How long can you have a positive OPK?

Again this answer varies. You may have a positive LH surge for a few hours, or less than a day, or you can have it up to 2 to 2.5 days. It depends on your cycle, as there is no set answer for this question, since every cycle is different.


How long will I take OPKs?

You will continue to take your OPKs until the LH surge is detected, and you receive a positive OPK (2 lines). That is why you want to begin testing early enough in your cycle to make sure you don’t miss the surge.

Many women peter out if not getting a positive result after a few days, when in fact, they are just missing the surge. It may be coming later in their cycle than they had anticipated. For this reason, you will want to stock up on ovulation tests, because they really are the easiest key to getting pregnant fast.

In drug stores, you can purchase sets of OPKs in packs of 7, 14 or 21. Ovulation test strips are even cheaper to pick up in bulk. The reason for the number is of course so you have enough to begin early enough in your cycle. About 90% of women will detect the LH surge within 10 days of testing.

You can even get 20 free ovulation tests just for trying the ConceiveEasy TTC Kit – so that can help you get a jumpstart on your ovulation testing.

TIP #12: You will take OPKs until you receive a positive result.


Bottom Line

Ovulation predictor kits are a fantastic and easy way to track your ovulation, to help you time intercourse properly during ovulation time. Yet at the same time, it is best not to rely solely on OPKs for ovulation prediction. Getting to know your body and keeping track of the changes in your cervical mucus in conjunction with using the kit is the best way to help create perfect timing for pregnancy to happen.

So be patient and keep the faith!

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Lucy Eades
Lucy Eades | ConceiveEasy
Lucy is a mother of three, who’s passionate about all things AP parenting. When she’s not busy giving tips on keeping babies healthy & happy, you can find her blogging on her popular YouTube channel