I know that it can be tempting to just say “screw it” to this whole charting business and just use OPKs to determine when you’re ovulating. But while OPKs can certainly be useful for detecting impending ovulation, they can sometimes be misleading and shouldn’t be relied upon alone as a means of determining your fertile days.
The thing is, OPKs can tell you when you may be approaching ovulation, but they don’t tell you if you ACTUALLY ovulated. There are instances in which a woman may have a positive ovulation test result, but not ovulate.Some women can experience false mini-peaks of luteinizing hormone (LH – the hormone released in a surge right before ovulation which is detected in urine by the ovulation tests) before their actual peak. Women with PCOS in particular can sometimes produce multiple LH surges during a cycle without ovulating at all. Women over 40 can have elevated levels of LH throughout their cycle, putting them at risk for false positives.
OPKs can also give false negatives. If a woman’s LH surge is less than 10 hours, and she tests only once a day, she may miss the surge and think she didn’t ovulate. Or, her body may not produce enough LH for the OPK to register a positive result, even though she did actually ovulate.
Certain drugs can throw off the validity of OPKs. These include most fertility drugs (especially those that contain LH, Follicle-Stimulating Hormone (FSH), or Human Chorionic Gonadotropin (HCG)), certain antibiotics, and hormone replacement therapy (HRT).
Finally, a positive ovulation test result doesn’t necessarily mean it’s the best time to try to conceive –if there isn’t any fertile cervical fluid in the vagina, that sperm is going nowhere.
If you’re trying to get pregnant, the most important things to track are your cervical fluid (to know when you’re becoming fertile), and your basal body temperatures (to confirm that ovulation occurred). Remember that the best time to try to conceive is just BEFORE ovulation – and the presence of eggwhite or watery cervical fluid should clue you in to this. Your temperatures will tell you when you ovulated after the fact.
All of this being said, OPKs CAN provide additional confirmation of the fertile window, and can be useful in particular for women who have just started to chart and are in the process of learning how to interpret their fertility signs. So, I’m not saying that you shouldn’t use OPKs - it’s perfectly fine to use them, just use them ALONG with tracking your temperatures and cervical fluid :)
Questions about OPKs? Check out our knowledge base or email us at firstname.lastname@example.org.
(P.S. Want a highly accurate basal thermometer that's fast, fits comfortably in your mouth, and doesn't beep? Try Wink, a bluetooth basal thermometer that automatically syncs your temperatures and the time your temperature was taken to the Kindara app.)