Proov PdG tests use a reverse reading system compared to most at-home hormone tests: one line means positive, and two lines means negative. This catches many people off guard, especially if you’re used to reading ovulation predictor kits or pregnancy tests where two lines signal a positive result. Understanding this key difference, along with when to test and what your pattern of results means, is essential for getting useful information from these strips.
Why One Line Means Positive
PdG (pregnanediol glucuronide) is a marker your body releases into urine after progesterone rises following ovulation. The Proov test is designed to turn positive when PdG reaches a threshold of 5 micrograms per milliliter in your urine, a level that clinical studies have linked to confirmed ovulation roughly 82% of the time.
Here’s how the lines work. The test strip always has a control line to show the test is functioning. When PdG levels are low (meaning ovulation hasn’t been confirmed), a second test line also appears, giving you two lines. When PdG is high enough to confirm ovulation, the test line disappears, leaving only the control line. So one line equals positive, two lines equals negative. This is the opposite of what most people expect, and it’s the single most common source of confusion with these tests.
A critical detail: even a very faint second line counts as negative when you’re reading by eye. Unlike pregnancy tests where a faint line is still a positive, a faint line on a Proov PdG strip means your PdG level hasn’t crossed the threshold. Don’t squint at it and call it positive. If you can see a second line at all, the result is negative.
When to Test During Your Cycle
Proov PdG tests aren’t meant for a single day. The testing protocol calls for testing on days 7, 8, 9, and 10 after your LH surge (the “peak” day identified by a standard ovulation test). This four-day window aligns with the implantation window, the stretch of your luteal phase when sustained progesterone matters most for a fertilized egg to implant.
To pinpoint day 1 of this count, you need to track your LH surge with ovulation predictor strips first. The first day you detect your LH surge is your peak day. Count forward seven days from that peak, and that’s when PdG testing begins. You’ll test once each morning for four consecutive days.
Use your first morning urine, collected in a cup rather than tested midstream. First morning urine is the most concentrated sample of the day, and PdG accumulates overnight, so this timing gives you the most accurate reading. Drinking large amounts of water before bed or testing later in the day can dilute your sample enough to produce a false negative.
Reading Your Four-Day Pattern
A single positive test doesn’t tell you much on its own. What matters is the pattern across all four days. The goal is to see positive results (one line only) on all four testing days, which indicates that your progesterone stayed elevated throughout the implantation window. Earlier clinical research on PdG testing established that three or more consecutive positive results confirms ovulation occurred and that progesterone remained adequately sustained.
If you get a mix of positive and negative results across those four days, it may suggest that progesterone rose but didn’t stay consistently elevated. For example, testing positive on days 7 and 8 but negative on days 9 and 10 could indicate a drop in progesterone during the window when steady levels matter most. Some users refer to this as “weak” ovulation, though it’s more accurately described as suboptimal luteal phase support.
If all four days show two lines (all negative), it could mean ovulation didn’t occur that cycle, or that progesterone levels never rose high enough to push PdG past the detection threshold.
Using the Proov Insight App
If you’re using the Proov Insight app, you can scan your test strips with your phone camera instead of reading the lines by eye. The app converts your results into an ovulation score on a scale of 0 to 100, calculated from your results across the testing window. Higher scores reflect more consistently elevated PdG levels. A clinical study found that users with high ovulation scores (indicating sustained PdG elevation during the implantation window) had a 75% increase in pregnancy rates compared to those with lower scores.
One thing worth noting: the app may interpret a borderline result slightly differently than your eyes do. Proov acknowledges that computers and human eyes read faint lines differently, so you might occasionally see a discrepancy between what you’d call the result visually and what the app reports. If you’re using the app, trust its reading over your own visual interpretation for borderline strips.
Common Mistakes That Affect Accuracy
The most frequent errors aren’t about reading the test itself but about the conditions around testing. Diluted urine is the biggest culprit for unreliable results. If you drink a lot of water in the evening or wake up multiple times at night, your first morning sample may not be concentrated enough. Aim for at least a few hours of uninterrupted sleep before collecting your sample.
Timing errors are also common. Miscounting from your LH surge by even one day shifts your entire testing window. If you’re unsure which day your LH surge started, it’s better to start PdG testing a day early (day 6 post-peak) than a day late, since testing too early will simply show a negative that you can disregard.
Reading the test too early or too late after dipping the strip can also skew results. Follow the specific wait time printed on your test kit’s instructions, as reading outside that window can cause evaporation lines or color changes that don’t reflect your actual PdG level.
What Your Results Actually Tell You
Proov PdG tests confirm whether ovulation likely occurred and whether progesterone stayed elevated afterward. They do not measure your exact progesterone level the way a blood test would. Think of them as a pass/fail check at a single threshold rather than a precise measurement.
The 5 microgram per milliliter cutoff used by Proov was validated against ultrasound-confirmed ovulation and chosen because it captured a higher percentage of confirmed ovulations (82%) than a more conservative 7 microgram threshold (59%). This means the test is calibrated to be sensitive enough to catch most ovulations, but a small percentage of cycles where ovulation did occur may still produce negative PdG results if progesterone was on the lower end.
If you consistently see low or mixed results across multiple cycles, that information is worth bringing to a healthcare provider, as it may point toward luteal phase issues that can be evaluated with blood progesterone testing and potentially addressed with targeted support.