Multi-Hormone and PdG Testing, Explained (Not Just Reviewed)
PdG (pregnanediol glucuronide) is what your body turns progesterone into before flushing it out in urine, and testing for it is a genuinely accurate way to confirm ovulation happened -- three days over the 5 microgram/mL threshold has shown 92% sensitivity and 100% specificity in research. A basic LH-only OPK, by contrast, can misclassify anywhere from roughly 3% to nearly 19% of cycles as ovulatory when they weren't.
You've probably seen "PdG" thrown around in ovulation-testing marketing without much explanation of what it actually is or why it matters. So let's back up and actually explain the science, rather than just reviewing which brand's app has the nicest interface.
What PdG actually is
PdG stands for pregnanediol glucuronide. When your body breaks down progesterone, PdG is one of the metabolites it produces on the way out, and it shows up reliably in urine -- which is what makes an at-home test for it possible at all. Progesterone itself is tricky to measure accurately outside a blood draw, but PdG tracks it closely enough that measuring the metabolite works nearly as well as measuring the hormone directly, and does it non-invasively.
After you ovulate, progesterone rises to help prepare and maintain the uterine lining. PdG follows that rise, typically showing up in urine about 24-36 hours after ovulation and continuing to climb through the early luteal phase. That's the biological reason a rise in PdG is treated as solid confirmation that an egg was actually released -- not just that your body geared up to release one, which is all an LH surge alone can tell you.
Why this matters: LH surges alone are not proof of ovulation
Here's the part a lot of ovulation-testing marketing glosses over: a positive OPK means your LH surged. It does not, on its own, guarantee that the follicle actually ruptured and released an egg. Research looking at urinary hormone algorithms found that LH-surge-based methods (the kind used in most over-the-counter OPKs and monitors) classified anywhere from about 3.4% to 18.6% of cycles as anovulatory depending on which algorithm was used -- and in general, LH-surge-only methods tended to flag more cycles as anovulatory (or miss confirming ovulation) compared to methods that also incorporated a luteal-phase progesterone or PdG measurement. In other words: if you're only using an LH strip, there's a real chance you're missing the full picture in a meaningful share of cycles, especially if your surges are unusual in timing, duration, or strength -- something that's more common than people assume.
PdG testing closes that specific gap. It's not "more advanced" so much as it's answering a genuinely different question: not "is my body about to ovulate," but "did ovulation actually happen."
How accurate is PdG testing, really?
Pretty accurate, as home testing goes. Research on the standard protocol -- three consecutive days of PdG readings over the 5 μg/mL threshold -- found 92.2% sensitivity and 100% specificity for confirming ovulation, when checked against the reference standard of serial ultrasound. A separate lab comparison found that PdG's rise after ovulation is dramatically larger and more consistent than what you see with automated blood-progesterone immunoassays: a median 427% increase for urinary PdG, versus 146-278% for two different automated blood progesterone tests. That bigger, cleaner signal is part of why PdG translates so well into a simple at-home strip: the difference between "before" and "after" is large enough that you don't need lab-grade precision to see it clearly.
How to actually use this
If you're already tracking with a basic LH strip, the cheapest way to add PdG confirmation is a standalone PdG test: once you get your LH peak, start testing about a week later and look for the line to fade over the disappearance threshold on three consecutive days. If you'd rather track everything -- LH, estrogen, and PdG -- on one device instead of stacking separate tests, that's exactly the gap that multi-hormone monitors like Inito, Mira, Proov, and Oova are built to fill; we've broken down how those four compare if you're trying to decide whether the convenience is worth the extra cost.
Either way, the takeaway is the same: predicting and confirming ovulation are genuinely two different jobs, and if you've been relying on an LH strip alone and wondering why your cycle still feels like a mystery, PdG is the piece that's been missing.
References
- Ecochard, R., Leiva, R., Bouchard, T., et al. (2013). Use of urinary pregnanediol 3-glucuronide to confirm ovulation. Steroids, 78(10), 1035-1040.
- Direito, A., et al. Confirmation of ovulation from urinary progesterone analysis: assessment of two automated assay platforms. Scientific Reports.
- FACTS About Fertility. (2025). Urinary pregnanediol-3-glucuronide to confirm ovulation: A review.
Common questions
Is PdG testing more accurate than a regular OPK?
They're not really measuring the same thing, so 'more accurate' isn't quite the right frame -- an OPK predicts a coming LH surge, while PdG confirms afterward that ovulation actually happened. Used alone, LH-based monitors have been shown to misclassify some genuinely anovulatory cycles as ovulatory; PdG testing closes that specific gap.
How soon after ovulation does PdG show up?
PdG typically rises about 24-36 hours after ovulation, then keeps climbing through the early luteal phase, which is why the standard protocol is to test starting a few days after your suspected ovulation date.
What's a 'multi-hormone monitor' vs. a plain PdG test?
A multi-hormone monitor (like Inito, Mira, Proov, or Oova) tracks several hormones -- often LH, estrogen, and PdG together -- on one device or app. A standalone PdG test just checks the one thing: whether progesterone rose enough to confirm ovulation. See our comparison of the actual monitor brands if you're deciding between them.