How to Use OPKs Correctly


Ovulation Predictor Kits, otherwise known as OPKs have become an easy way to track your fertile window, allowing you to better understand your fertility and help you get pregnant faster. However, if you are not using these tools correctly, you could completely miss your fertile window preventing you from getting pregnant that month. So here is what you need to know when using OPKs.

How do OPKs work?

Ovulation Predictor Kits work in a similar fashion as a traditional at-home urine pregnancy test but instead of detecting Hcg (Human chorionic gonadotropin), the pregnancy hormone, OPKs will detect a different hormone, known as Luteinizing hormone (LH). LH is the hormone released by the brain, specifically the anterior pituitary gland, to trigger ovulation. The idea behind OPKs is to detect when an LH surge occurs, which will indicate ovulation is approaching. Because LH hormone is typically released in the morning, it is best to test your urine between 10-2pm as this allows the LH hormone to end up in the urine and can be detected by the OPKs. If you use OPKs first thing in the morning or late at night, you may completely miss your LH surge, which means you can miss your fertile window for that month. Missing your LH surge can also make you think you didn’t ovulate, when it fact, you may have ovulated but simply tested at the wrong time.

When day should I start using OPKs?

For most women, you can start taking the test around cycle Day 10. Remember Day 1 of your cycle is the first day of bleeding NOT spotting. This means, if you have one day of spotting prior to starting your period, do not count that day of spotting as Day 1, count instead the first day of actual bleeding. Take the OPK test every day from Day 10 until your positive LH surge. The newer OPKs will give you high LH readings as well as a peak LH reading. The peak LH reading will be the day you are looking for, since this should be the highest reading you will get and will indicate approaching ovulation. Remember the kit detects an LH surge not actually ovulation. The LH surge will occur the day BEFORE you ovulate, which means once you get an LH surge, you will likely ovulate in the next 24 hours, so it’s time to get baby busy.

How long after a positive ovulation test are you fertile?

Each month an egg should be released from the ovaries. Once the egg is released at ovulation it only lives for 24 hours. Sperm, on the other hand, can live in the female reproductive tract for up to five days. This is why we typically say your fertile window is five days, ending on the day of ovulation. Having sex in two day intervals (meaning every other day) ending on the day of ovulation has been shown in studies to be associated with the highest chance of getting pregnant naturally. Also remember that sperm CAN live in the female reproductive tract for five days but that doesn’t mean it will, so make sure to have intercourse every other day throughout your fertile window.

Do I need to continue testing after a positive OPK?

Once you get a positive LH surge, there is no reason to continue testing for that month. Remember, a positive LH surge occurs the day BEFORE you ovulate, which means the two most fertile days of that month are the day of the positive LH surge and the day AFTER, since this is the day you actually ovulate. If you do not get pregnant in that month, you will need to continue to use OPKs with sub-sequential months.

Can False Positives happen?

Unfortunately, yes. This is most common in women with Polycystic Ovarian Syndrome (PCOS). The reason this occurs is because women with PCOS typically have multiple cysts on their ovaries. These cysts can release elevated levels of estrogen and trick the test in thinking ovulation is approaching, when it fact, it is not. This can be extremely frustrating for women with PCOS, which is why I do not recommend only using OPKs to track your fertility if you suffer from PCOS.

Should I Use OPks if I’m on Clomid/ clomiphene?

Clomid is often used to help women ovulate. This is a common medication used for patients struggling to conceive especially, in those with PCOS. Because women with PCOS often have irregular cycles, OPKs can be a great way to find your fertile window.

Dr. Zen’s Favorite OPKs

There are a variety of great OPK options, so here is what you need to know when shopping for OPKs.

1) First things first, if you are buying them online, please check the expiration date. I, unfortunately, have experienced patients using expired OPKs, which obviously is not going to be accurate. This sounds simple and can be an easy reason as to why you aren’t seeing an LH surge.

2) OPKs are getting more advanced which is great. However, it is important to know what your specific OPK test is detecting. For example, there are newer OPKs which are able to tell you the five days leading up to ovulation. This is known as your “fertile window”. These tests are detecting estrogen levels NOT LH. Remember LH is only released 24 hours prior to ovulation. For women with PCOS, I highly recommend staying away from these particular tests because women with PCOS already have higher than normal estrogen which can lead to false positive results.

3) Timing is EVERYTHING. Just as I mentioned earlier using the OPKs between 10-2pm starting on Day 10 is the most accurate.

My Favorite OPKS

  • Femometer 50 Ovulation Test Strips which directly sync to your Femometer app allowing you to keep track in a simple and easy way.

  • Clearblue Advanced Digital Ovulation Predictor KITs (includes advanced Ovulation tests with digital results and 20 ovulation test)

  • Proov - at-home progesterone kit. Remember that progesterone will raise AFTER ovulation so this is best used in conjunction with standard LH surge OPKs. (Use Promo code PROOVIT for 10% off)

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Having trouble getting pregnant? At NMD Wellness of Scottsdale, we offer personalized integrative solutions for all your hormone and fertility needs.

Dr. Zen is a licensed naturopathic physician specializing in Women's Hormones and Fertility. Her local private practice is located in Scottsdale, Arizona, however, she works with patients around the world. Her goal is to educate, inspire and empower women to take control of their health naturally. She believes in providing integrative healthcare options that get to the root cause of your unique symptoms. She has been featured as an expert in a variety of publications including Shape, Elite Daily and Forbes.

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