The genius of at-home ovulation test strips is their ability to measure hormone levels in your urine so you can pinpoint the best time to get pregnant. And yet, as sensitive as an ovulation predictor kit (OPK) is, it isn’t designed to detect whether you’ve actually conceived.
But can an ovulation test ever show you whether you're pregnant? The answer: It's complicated.
Here’s more about whether ovulation tests can detect pregnancy, as well as the difference between drugstore ovulation tests and pregnancy tests. Plus, know the signs of ovulation and early pregnancy symptoms so you can track any subtle changes in your body.
Can an ovulation test detect pregnancy?
Ovulation tests can in some cases detect a pregnancy, says Dr. Aaron Styer, a member of the What to Expect Medical Review Board and the co-medical director of CCRM Boston.
OPKs and home pregnancy tests (HPTs) both measure hormone levels in the urine, and these reproductive hormones are alike in makeup and function. The result? Your ovulation test may remain “positive” for ovulation for several days, but you may really be pregnant.
“An ovulation predictor kit may detect an unrecognized pregnancy" because of the similiarity in the hormones involved, explains Dr. Styer.
What’s the difference between an ovulation test and a pregnancy test?
The difference between an ovulation predictor kit[1] and a pregnancy test relates to the hormones they’re designed to detect.
“Urine ovulation kits are made to find the luteinizing hormone, or LH,”[2] which is made in the brain and signals ovulation (i.e. when your ovary releases an egg), says Dr. Styer.
Home pregnancy tests can detect a different hormone called human chorionic gonadotropin (hCG). Those handy pee sticks you use to check whether you're pregnant “have been developed to detect hCG, which is released by the embryo (aka fertilized egg) when it’s been implanted in the lining of the uterus during early pregnancy,” says Dr. Styer.
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Is an ovulation test positive if you’re pregnant?
An OPK can be positive if you’re pregnant — but it’s quite possible it’s a false positive. “LH and hCG have very similar molecular structures, and the over-the-counter predictor kits aren’t sensitive enough to distinguish between these two hormones,” says Dr. Styer.
As a result, the test strip might pick up rising hCG levels in your urine instead of LH.
“And if you’re actually pregnant and unaware of this fact when you’re using an OPK, it may read positive and incorrectly indicate that you’re ovulating,” Dr. Styer says.
How can an ovulation test detect pregnancy?
The reason that an ovulation predictor kit can detect pregnancy is because “it’s erroneously detecting the high hCG levels of a pregnancy and not LH,” explains Dr. Styer.
Keep in mind that OTC urine kits aren’t made to be as sensitive as blood tests administered by a doctor.
The fix for this situation? “If you find you have a positive ovulation strip in hand and you don’t have your period within 14 to 18 days of that result, you can take a urine pregnancy test to confirm whether you’re indeed pregnant," says Dr. Styer.
And if you need additional confirmation, ask the doctor to order a blood draw for pregnancy, also known as a serum hCG-quantitative test.
When should you take an ovulation test?
To use an OPK, look to your monthly menstrual cycle. Ovulation usually takes place at the cycle’s halfway point, so your best bet is to take the ovulation test a few days before that.
For example, for a 28-day cycle, take the test on day 10 or 11. But if your period is irregular, pick the shortest cycle over the last six months and test a few days before the midpoint of that one.
Having trouble seeing the LH surge on the test strip? Be sure to follow the directions carefully and then take the test for a few days so you note the LH change (the kit probably comes with several strips).
As for the best time to test, aim for between 12 p.m. and 8 p.m., as most women have an LH surge in the morning, which means the OPK should find it by midday.
How do you know whether you’re ovulating or pregnant?
As you test for ovulation, it’s a good idea to also become familiar with the subtle symptoms of early pregnancy. Remember, the signs of both can overlap, and a few ovulation symptoms can mimic those of a period on the way.
Remember that some women notice several of the following symptoms of pregnancy and signs of ovulation, while others might have only a couple — or none at all.
Ovulation signs
Uptick in basal body temperature (BBT)
Change in consistency of cervical mucus
Mild cramps in lower belly
Boost in libido
Tender breasts
Bloating
Sharper sense of smell
Changes in appetite
Mood swings
- Vulva changes
Early pregnancy signs
Higher basal body temperature
Sore breasts and darker, bumpy areolas
Trying to conceive can sometimes feel like you’re back in chemistry class. If you have questions when you're trying for a baby and tracking ovulation, know that your doctor can provide answers and advice when it comes to when and how to use ovulation test strips.
And even if you feel twinges in your body that make you suspect there's a baby on board, don’t use an ovulation predictor kit to find out whether you're pregnant or not. Instead, wait until after your period is supposed to arrive and then check your urine with a home pregnancy test. Good luck!
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