Ovulation test strips, or ovulation predictor kits (OPKs) are at-home tests you can use to predict ovulation. You can use these strips on their own or in combination with basal body temperature tracking (BBT) and/or cervical mucous monitoring if you would prefer multiple methods of determining ovulation.

How do they work?

Ovulation test strips are used to detect the presence of luteinizing hormone (LH) in your urine.
LH is secreted in varying amounts by the brain throughout the whole menstrual cycle. In the 24-48 hours before ovulation, the level of luteinizing hormone rises or “surges” to stimulate ovulation by the ovary. This surge lasts 12-24 hours. Ovulation will then occur 1-2 days after the rise of LH.

What am I looking for?

You will notice after taking a sample, the ovulation test strips will have 2 lines – one is the control line which lets you know whether the test was done correctly and is working properly. The second is the test line which represents your LH levels to which you will compare to the control line. This test line will change in darkness depending on your LH levels. When the test line matches the colour of the control line, it indicates your LH has surged and ovulation will be occurring soon.

When do I ovulate?

Ovulation typically occurs mid-cycle, for example Day 14 of a 28 day cycle. Keep in mind this is not the case for everyone!  Based on what women tell me in office about their cycles and OPK results, some women may ovulate 1 or 2 days either side of Day 14. It’s not uncommon for women with longer cycles (>32-35 days) to ovulate later in their cycle, for example on Day 18 or 19. If you have a longer cycle where you skip a menses for 1-2 months or more, it can be difficult to figure out when you are ovulating. Ovulation test strips provide useful information in this case!

When to begin testing?

If you know or suspect the day you ovulate, you can start testing 5 days before expected ovulation. You should see a faint test line which will become darker in colour the closer you get to ovulation. When the test strip line matches the colour of the control line, it indicates your LH surge is occurring. Ovulation will happen 1-2 days later (some sources state 24-36 hrs later).

If you do not know when you ovulate, but you have a 21-35 day cycle, I recommend starting ovulation test strips on Day 10 of your cycle (recall that the first day of menstrual flow is Day 1 of a cycle) and test until you find the LH surge.

If your cycle is longer than 35 days, I would still recommend starting ovulation test strips on Day 10. This way, if you do ovulate around Day 14, you will have started early enough to find the LH surge. If you dot not ovulate around Day 14, you will want to continue testing daily until the LH surge occurs.

What are the pros and cons? 

The advantages to OPKs is that it will tell you when ovulation is approaching, rather than after ovulation like basal body temperature (BBT) does. If you are trying to conceive, this will inform you to plan intercourse that day and/or for the next few days. OPKs are also a great tool for those who work shift work, as BBT can it be affected by switching between night and day shifts, while LH is not affected. A disadvantage of OPKs is that it can become expensive, especially if you have long cycles and take LH tests for days or weeks on end. It’s good to note that women with PCOS tend to have high levels of LH throughout the month which can falsely indicate ovulation, and this can make it confusing whether you are ovulating or not. This is when other ovulation tracking tools become helpful to add in.

Overall, if you are wanting to track ovulation, it is best to consider which method(s) may be best and easiest for you – ovulation test strips, BBT, and/or cervical mucous tracking.

Dr. Stephanie Liebrecht, BSc, ND
Naturopathic Doctor