Content table
False positive on an ovulation test is not an urban fertility myth.
While ovulation tests pinpoint when you’re most fertile so you can time the deed for higher pregnancy chances, they can be confusing and frustrating—especially if you’re not aware of their limitations.
In this article, we’ll tell you why you may get a false positive on an ovulation test, how to get accurate results, and how Ovulation Predictor Kits (OPKs) work.
Let’s begin!
Takeaways
- Ovulation predictor kits detect luteinizing hormone (LH) in your urine to tell when you’re approaching ovulation.
- A positive ovulation test result is when the test line looks as dark or darker than the control line.
- False positive results may be due to cross-reactivity, pregnancy, PCOS, prescription drugs, and certain types of LH surges.
- For the best accuracy and to avoid missing the surge, follow the instructions exactly and test twice a day.
- OPKs predict ovulation, but don’t confirm it. Since progesterone rises after an egg is released, tracking PdG can confirm that successful ovulation occurred.
What are OPKs?
Ovulation Predictor Kits (OPKS) or ovulation tests predict ovulation by detecting the Luteinizing Hormone (LH) levels in your urine.
Around 24-36 hours before you ovulate, LH surges. This triggers the follicle to open up and release the mature egg.
Once released, an egg survives for roughly 12-24 hours. That’s why knowing when you’re ovulating is crucial when you’re trying to get pregnant.
That way, you can time sex on the days you’re most fertile, so you have the best chance of conception.
How do OPKs work?
Ovulation tests measure how much LH is in your urine. Most ovulation test kits base their results on average thresholds. That means they only detect LH levels above 25-30 mIU/mL. If your LH passes that amount, you get a positive result.
Most ovulation predictor kits typically come with two lines: a control line and a test line. The control just shows the test is working. The test line is what gives your result.
The trouble is that reading ovulation kits can be tricky.
What do positive results look like on OPKS?
Reading a pregnancy test is as plain as day. Two lines = You’re pregnant! But OPKs aren’t so cut and dry.
For a positive OPK, the test line must be at least as dark as the control line, or darker. If an OPK detects a small amount of LH in your urine, the test line may show up as a faint line.
However, a faint line does not equal a positive ovulation test. This could mean:
- LH was detected but isn’t at surge levels
- LH hasn’t spiked yet, or
- The LH surge has already passed
Read more about faint lines on an ovulation test: What Does a Faint Line on an Ovulation Test Mean?
Along with LH, some ovulation tests measure estrogen as well. This is because estrogen rises about three days before you ovulate.
Knowing when your estrogen is rising gives you a better prediction of your fertile window. Hence, you can time intercourse within the fertile window as sperm can survive for up to 4-5 days. The more sperm in your body when an egg drops, the better your chances of conceiving.
That’s because sperm can survive for up to 4-5 days. So, the more sperm in your body when an egg drops, the better your chances of conceiving.
Learn more: Positive Ovulation Test: How Long Am I Fertile After a Positive Ovulation Test?
Know your chances of Ovulation!
Take our ovulation quiz to understand how your hormone patterns and
lifestyle factors may affect your chances of ovulating
What causes a false positive ovulation test?
When used correctly, ovulation tests predict the LH surge with up to 95% accuracy. However, an LH surge can only predict ovulation and doesn’t always guarantee ovulation.
And since LH surges vary, some OPKs may not be sensitive enough to pick up your surge. Certain health conditions like PCOS can also muck up your results on OPKs.
Here are six reasons why false positives happen:
1. Anovulatory cycles
It is possible that your LH surged, but it did not trigger ovulation. This can result in anovulation. The surge in LH can give you a false positive result on your OPK.
It’s not uncommon to have an anovulatory cycle now and then. But chronic anovulation can cause fertility problems.
2. LH surge type
All LH surges were once believed to be short with one dramatic peak. But that’s not the case. LH surges vary by their onset and pattern. And the type of surge you have will affect your OPK results.
Rapid surge
For example, only 42.9% of LH surges are rapid, meaning they’re over within a day. If you have a short surge, you could get a positive ovulation test in the morning and a negative one that night.
Around 57.1% of women have gradual surges that stretch out over 2-6 days. In this case, LH will stay high for the length of your surge. That means you’d get positive results several days in a row. This also depends on the type of gradual onset surge you have:
Biphasic surge
About 44.2% of women have biphasic surges, meaning LH spikes twice. An OPK may show a positive result for both spikes if you have a double surge.
Plateau surge
Around 13.9% of surges follow a plateau pattern, meaning LH peaks and stays high for several days. If you have this surge pattern, you may get a positive OPK for the entire plateau.
3. Alpha beta cross-reactivity
Hormones like LH, FSH, hCG, and TSH are made up of beta and alpha subunits. Although the alpha subunits are identical, the beta subunits give each hormone its unique characteristics.
Here’s the problem—many ovulation predictor kits measure alpha LH. This may lead to cross-reactivity, meaning the test detects FSH, hCG, or TSH but reads it as LH, which can lead to false positive results.
Or when someone takes an hCG trigger shot to induce ovulation, the OPKs read it as LH and give you a false positive result.
One easy way to avoid this is to choose an ovulation test that measures beta LH, like Inito. Since beta subunits are distinct, there’s less chance for cross-reaction.
4. Polycystic ovary syndrome (PCOS)
PCOS is a hormonal imbalance marked by high levels of androgens. This throws off other hormones, including LH.
Women with PCOS often have high LH levels nonstop. This can result in ovulation for some, that’s not the case for many. Sometimes, ovulation just doesn’t occur due to the high LH levels. This gives you a false positive result on an OPK for many days. But you ovulate only once during your entire cycle.
5. Prescription drugs
According to the American Pregnancy Association, the following medications may throw off your ovulation test results:
- Pergonal
- Danazol
- hCG injections
- Clomid
- Serophene
Some of these drugs help stimulate ovulation, while others suppress ovarian function. Either way, they can lead to inaccurate results.
If you’re trying to conceive and are taking any of these medications, talk with your doctor before using an OPK. They can recommend when to start testing to get the best accuracy.
6. Pregnancy
If you’re pregnant or were recently pregnant, this can interfere with your results on OPKs.
When you’re pregnant, your body produces the human chorionic gonadotropin hormone (hCG). Pregnancy tests detect hCG in your pee to deliver a positive result.
hCG has a structure that’s very similar to LH. So much so that some ovulation predictor kits mistake hCG for LH. This can lead to a false positive result.
See how your hormone chart might look like!
Answer some questions to help us provide you a free personalized hormone chart customized to your hormonal health and conditions
How do I avoid false positives?
You can reduce your risk of getting a false positive with these tips:
Test correctly
For the most accurate results, follow these best practices:
- Check the expiration date. If the ovulation kit has expired, get a new one.
- Test twice a day. If you have a quick LH surge and test once a day, you could miss it.
- Follow the instructions exactly. Each OPK will vary somewhat.
- Test with your second-morning urine. LH surges usually happen between midnight and 8 am. But it can take 3-6 hours to show up in your pee.
- Avoid drinking a lot of water before testing. This may dilute your urine and skew your results.
- Try not to pee for 4 hours before taking the test. That way LH will be more concentrated in your pee.
Keep in mind that these tips will not change the fact that you’re getting a false positive due to the problems mentioned above.
However, testing correctly can give you peace of mind that a false positive isn’t due to faulty testing.
Use a digital test
Reading ovulation test strips can be confusing. You may be unable to tell whether the test line is dark enough to indicate a positive result.
One easy way to avoid this is to choose a digital test.
Digital tests are way easier to read. Instead of wracking your brain analyzing the dark test line, you get clear-cut results (like a happy face or the word ‘fertile’). That said, cross-reactivity is still risky if your digital test measures alpha LH.
Track PdG along with LH
It’s possible for LH to surge and still not ovulate. Remember, the rise in LH predicts ovulation. But it doesn’t guarantee it.
To confirm ovulation, you’ll want to track PdG. This is a metabolite of progesterone, which rises just after an egg is released. If you see PdG shoot up after LH surges, you can rest easy that ovulation occurred.
Know more about different scenarios of anovulation.
What should I do if I get a false positive?
The best way to know when you’re ovulating is to track your hormones. The better you understand your cycle, the better your chances of getting pregnant.
FSH, estrogen, and LH all help predict your 6-day fertile window. And progesterone’s rise is what confirms ovulation.
Try using the Inito Fertility Monitor, which measures your LH, FSH, estrogen, and PdG (urine metabolite of progesterone) all in a single test strip. Tracking this foursome gives you a clearer picture of your entire fertility window. But it also confirms ovulation really happened. Inito also tests beta LH, so there’s less risk of cross-reactions.
Read more about ovulation symptoms.
Common questions (answered) on ovulation tests
Ovulation tests can bring up a lot of unanswered questions. So, let’s clear some of them up:
How long will an ovulation test stay positive?
That depends on the length of your LH surge. Women with short surges may get a positive result one day and a negative result the next. But if you have a gradual surge, you may get a positive test result for up to 6 days.
Can sperm cause a false positive?
No. Ovulation tests base their results on your hormone levels. So, sperm will not affect your results. However, semen may probably cause a false positive since it has some amount of LH. Although there is no evidence for this.
What are my chances of getting pregnant after a positive ovulation test?
It depends on which day you have sex in your fertile window. According to one study from Fertility and Sterility, the day before ovulation occurs is your best bet, with a 41% chance of conceiving.
FAQs
Yes, this is a definitely a possibility for a few reasons. The first has to do with how ovulation tests work. Most urine LH tests give you a positive result if your LH levels go above 25 mIU/mL. But for some women, their natural baseline levels of LH may already be that high even without a surge. This would result in a false positive ovulation test. The opposite is also true – if your natural baseline levels are low, you will get a false negative result.
Second, some women have more than one LH surge in the same cycle, but only one of those surges leads to ovulation. This means that they could get a positive ovulation test when they’re experiencing an LH surge that doesn’t result in ovulation.
Thirdly, if you are pregnant, have PCOS, or take certain fertility medications, you could get incorrect ovulation test results.
This could happen if your natural baseline LH levels are on the higher side. Ovulation tests function on threshold levels of LH. This average threshold is usually around 25-30 mIU/mL. This means any amount of LH above this threshold will show a positive result. So if your baseline LH levels are already 25 mIU/mL or above, you’ll get a positive ovulation test even if you’re not having a surge.
Yes, you can get a positive ovulation test but not get a period. One reason this can happen is if you have irregular menstrual periods. It could also happen if you are pregnant, if you have PCOS, or if your ovulation test was inaccurate.
This could mean that you have a rapid LH surge pattern. With this pattern, your LH levels surge and then drop back down within a couple of hours. So if you test in the evening after getting a positive, it means that your surge may have ended already. There are several different LH surge patterns that are normal, and this is one of them. So it’s nothing to be worried about. It just means that in order to capture your surge, you’ll need to be on top of testing twice a day.
Yes, false positive ovulation tests are possible. You can get a false positive test if you have higher baseline LH levels or if you have a different LH surge type (double peak, multiple peaks, or plateau LH surge).
False positive ovulation tests can also happen if you’re on certain medications if you have PCOS, or if you’re already pregnant. In some cases, an ovulation test may even give faulty results due to the cross-reaction of LH and hCG. This is because alpha LH and alpha hCG are identical in structure and the test confuses which hormone it’s detecting.
Yes, women with PCOS have irregular LH patterns. Their LH levels are likely to peak several times throughout their cycle. And often, they have anovulatory cycles (which means they’re not ovulating). So if you have PCOS and you use an OPK, your LH test strip may give you a high fertility reading when in fact you’re not actually ovulating. This would be a false positive ovulation test.
Yes, an ovulation test can be wrong. It is possible to get false positive and false negative results on an ovulation test due to hormonal imbalances, lifestyle factors, improper testing, medications and any underlying conditions.
Was this article helpful?
- Urinary Luteinizing Hormone Tests: Which Concentration Threshold Best Predicts Ovulation? – PMC
- Breaking Research Reveals That Not All Home Ovulation Tests Are Equally Reliable | AACC.org
- Detection of ovulation, a review of currently available methods – PMC
- Characteristics of the urinary luteinizing hormone surge in young ovulatory women – Fertility and Sterility
- Structure–Function Relationships of Glycoprotein Hormones and Their Subunits’ Ancestors – PMC
- How to Use Ovulation Kits & Fertility Monitors
- Onset of the preovulatory luteinizing hormone surge: diurnal timing and critical follicular prerequisites – Fertility and Sterility
+2K others have already subscribed
