Clearblue is a home diagnostics brand that makes pregnancy tests, ovulation tests, and fertility monitors. Owned by Unilever, the brand launched the world’s first one-step pregnancy test in 1988 and has since expanded into a range of products designed to help people detect pregnancy early and identify their most fertile days each cycle.
How Clearblue Pregnancy Tests Work
All Clearblue pregnancy tests detect a hormone called hCG (human chorionic gonadotropin) in urine. Your body starts producing hCG shortly after a fertilized egg implants in the uterus, and levels roughly double every two to three days in early pregnancy. Clearblue’s manual and digital pregnancy tests can detect hCG at concentrations as low as 22 mIU/mL, which is sensitive enough to pick up a pregnancy around the time of a missed period or, in some cases, a few days before.
The brand sells several versions. The basic line tests show results as colored lines, similar to most home pregnancy tests. The digital versions display the words “Pregnant” or “Not Pregnant” on a small screen, which eliminates the guesswork of interpreting faint lines. In a study comparing how accurately women read different home pregnancy tests, Clearblue’s digital test had over 95% agreement between what volunteers reported and the actual result. Some competing line-based tests scored as low as 33% to 39% agreement, meaning users frequently misread them.
The Weeks Indicator Feature
One of Clearblue’s more distinctive products is the Digital Pregnancy Test with Weeks Indicator. Beyond telling you whether you’re pregnant, it estimates how far along you are by measuring your hCG concentration against a set of thresholds. If your hCG level is above the detection threshold but below 153 mIU/mL, it displays “1-2 weeks.” Between 153 and 2,750 mIU/mL, it shows “2-3 weeks.” Above 2,750 mIU/mL, it reads “3+ weeks.” These timeframes refer to weeks since conception, not weeks since your last period, so they’ll typically read about two weeks less than what a doctor would tell you.
A study published in Fertility and Sterility found that the weeks estimate agreed with the time since ovulation 93% of the time when normal measurement variability was accounted for. When compared against ultrasound dating, agreement reached 99%. That makes it a reasonably reliable early snapshot, though your doctor will still use ultrasound to confirm gestational age at your first prenatal visit.
Clearblue Ovulation Tests
Clearblue also makes ovulation tests designed to help you pinpoint your fertile window each month. The most basic version detects a surge in luteinizing hormone (LH), which typically spikes 24 to 36 hours before ovulation. When it detects the surge, you see a “Peak Fertility” result, meaning ovulation is imminent.
The Advanced Digital Ovulation Test goes a step further by tracking two hormones instead of one. In addition to LH, it monitors a form of estrogen that rises in the days leading up to ovulation. This gives you a wider fertile window. When estrogen levels begin climbing above your personal baseline, the test displays “High Fertility,” alerting you that your fertile days have started. When the LH surge hits on top of that, the result switches to “Peak Fertility.” This dual-hormone approach can identify up to four or more fertile days per cycle, compared to the two days a standard LH-only test typically catches.
The Clearblue Fertility Monitor
For people who want the most detailed tracking, Clearblue offers a standalone fertility monitor. It’s a handheld device with a touchscreen that reads disposable test sticks. Like the advanced ovulation test, it tracks both LH and estrogen, but it stores your data across multiple cycles so it can learn your personal hormone patterns over time. The monitor tells you each morning whether you’re at low, high, or peak fertility, making it useful both for trying to conceive and for understanding your cycle in general.
A study published in the journal Fertility and Sterility found that couples using the Clearblue Fertility Monitor had higher pregnancy rates compared to couples who did not use a monitor, largely because it helped them time intercourse more precisely within the fertile window.
What Can Cause Inaccurate Results
Clearblue tests are generally reliable, but certain situations can throw off results. False positives on pregnancy tests, where the test says pregnant when you’re not, can happen if you’re taking fertility medications that contain hCG. Some antipsychotic medications, certain anti-seizure drugs, and specific anti-nausea medications have also been associated with false-positive results on home pregnancy tests.
False negatives are more common and usually happen for simpler reasons: testing too early before hCG has built up enough, using a test that’s expired, or not following the instructions precisely (like not holding the test in the urine stream long enough). An early miscarriage can also produce a brief positive result followed by a negative one, since hCG levels drop quickly after a pregnancy ends.
For ovulation tests, results can be less reliable if you have a condition that affects your hormone patterns, such as polycystic ovary syndrome (PCOS), because LH levels may be elevated at times outside of ovulation. If your cycles are very irregular, ovulation tests of any brand become harder to time correctly.
Choosing Between Clearblue Products
Which Clearblue product makes sense depends on what you’re trying to do. If you just need to know whether you’re pregnant, the basic line test is the most affordable option and uses the same detection technology as the digital versions. If you find line tests stressful to read, the digital version removes ambiguity with a clear word-based result. The weeks indicator adds an early estimate of how far along you are, which some people find reassuring while waiting for a first doctor’s appointment.
For ovulation tracking, the standard test works well if your cycles are fairly regular and you just need to confirm your LH surge. The advanced digital version is more helpful if you want extra lead time before ovulation or if you’ve had trouble catching your surge with basic tests. The fertility monitor is the most comprehensive (and most expensive) option, best suited for people who plan to track over several months and want cycle-to-cycle data.
All of these products are available over the counter at most pharmacies and major retailers. No prescription is needed, and results from any of the tests are available within a few minutes.