PdG (Pregnanediol Glucuronide)

What PdG Measures

PdG isn't a hormone. It's what's left after the body is done with one. Once progesterone has circulated, the body inactivates it by reducing it to pregnanediol and attaching a glucuronic acid group, which makes the molecule water-soluble enough to exit in urine.^[1] So a PdG reading is an indirect look at recent progesterone activity. And since progesterone comes mainly from the corpus luteum, the structure that forms after an egg releases, PdG follows the same shape in urine that progesterone traces in blood. It stays low through the follicular phase and rises through the luteal phase.^[2]

How It's Measured

Labs can measure PdG quantitatively with immunoassays, an approach researchers have used for decades to study cycles without blood draws.^[1] At home, PdG shows up as lateral-flow strip tests and digital monitors that read a urine sample, usually first-morning urine, and report whether PdG has risen.^[4] That's the appeal over a serum progesterone test. Blood testing is invasive and can mean repeated needle sticks, while urine collection is easy to repeat day after day.^[1]

Why People Track PdG

Mostly to answer one question: did ovulation actually happen this cycle? An LH surge on an OPK points at ovulation ahead of time, but LH rises before the egg releases, so it can't confirm the release itself. PdG works from the other side. Its rise comes after ovulation, so it confirms the event looking backward, the same way a basal body temperature shift does.^[2] That makes it a staple in fertility awareness methods, and people trying to conceive use home PdG strips as an add-on to mucus and LH observations.^[4]

For how PdG strips compare with the other tests in the at-home hormone aisle, see our guide to at-home hormone tests.

How Go Go Gaia Tracks PdG

Go Go Gaia gives you a 1-click log for PdG test results, and you can bring in readings from at-home hormone monitors too. The app charts each result against your cycle day, right next to your BBT and LH logs, so your predictive signals and your confirming signal sit on one timeline instead of in three separate apps.

What the Research Shows

In a study that followed 40 normally menstruating women through a full cycle with daily urine samples, blood draws, and ultrasound, serum and urinary hormone profiles showed excellent agreement, and the rise in progesterone and PdG above baseline was a consistent marker that ovulation had occurred.^[2] A 2023 study of a home-use fertility monitor found the same relationship at the device level, with urinary PdG readings correlating strongly with same-day serum progesterone.^[3]

Home strip tests have early evidence behind them too. A 2019 pilot study of a home lateral-flow PdG test used alongside fertility awareness methods reported high specificity for confirming ovulation, and its authors recommended a larger trial as the next step.^[4] A review of ovulation-detection methods likewise lists sustained urinary PdG elevation as an accepted way to confirm that ovulation took place.^[5]

Related Terms

Frequently Asked Questions

Educational information based on published sources. Not medical advice. For personal concerns, please consult your doctor.

What's the difference between a PdG test and an ovulation test (OPK)?

They sit on opposite sides of ovulation. An OPK detects the LH surge, which comes before an egg releases, so it points at ovulation ahead of time. A PdG test detects the metabolite of progesterone, which rises only after ovulation, so it looks back and confirms the event. Many people use both together.^[2]

Can a PdG test predict ovulation?

No. Progesterone stays low until the corpus luteum forms after ovulation, so its metabolite can't rise in urine until the event has already happened. PdG works like basal body temperature in that sense. Both are retrospective signals that confirm ovulation rather than forecast it.^[2]

Is a PdG test the same as a progesterone blood test?

No. A blood test measures progesterone itself from a serum sample. A PdG test measures the leftover metabolite from a urine sample. Research comparing the two routes across full cycles found the profiles agree well at the population level, but they're different molecules measured through different routes.^[2][3]