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Trying to understand fertility can feel like a guessing game. But what if you had information that could help you confirm ovulation?
There are two different ways to confirm ovulation– a blood test or a urine test.
Think of these tests as different ways to get the same info. They are both accurate, but the results look different.
A blood test measures the amount of progesterone in your blood before it is metabolized by the liver. A urine test measures the amount of PdG (urine metabolite of progesterone).
Let’s dive into each type to help understand blood progesterone vs. PdG tests.
First, let’s look at what progesterone does and why you need it for a healthy pregnancy.
What is progesterone?
Progesterone is the dominant hormone in the second half of your menstrual cycle. Progesterone levels rise during this time to prepare your body for pregnancy.
After ovulation, the follicle that releases the egg forms a structure called the corpus luteum.
The corpus luteum is in charge of secreting progesterone so that the uterine lining can thicken and an embryo can attach (a.k.a. implantation).
If fertilization occurs and an embryo attaches to the uterine lining, progesterone stays elevated to support a healthy pregnancy.
But if fertilization does not occur, progesterone levels decrease and the uterine lining sheds, causing your period.
The up and down of progesterone levels feels a bit like a rollercoaster! But the importance of progesterone cannot be understated.
Here are some key roles of progesterone:
- Thickens uterine lining to prepare for implantation
- Prevents uterine contractions
- Prevents the mother’s immune system from rejecting the fetus
- Prevents ovulation so you can’t become pregnant again
- Stimulates breast tissue development so you can produce milk and breastfeed
Progesterone is one heck of a fertility hormone. So what is PdG and how does it compare?
What is PdG?
PdG (pregnanediol glucuronide) is the urine metabolite of progesterone. But what exactly does that mean?
Well, when progesterone is produced by the corpus luteum it is released into the bloodstream to circulate throughout the body. From here it exerts its effects like thickening the uterine lining.
After this, progesterone passes through the liver where it is metabolized to then be excreted through the urine. This metabolization process turns progesterone to PdG
Consider it a little chemical transformation – from progesterone to PdG.
Now that we understand the difference between progesterone and PdG, let’s look at how their tests differ.
Progesterone test vs PdG test
A progesterone test measures how much progesterone is in your blood. And a PdG test measures how much PdG is in your urine.
These tests are performed differently and often for different reasons.
One of the main reasons your doctor may order a progesterone test is to confirm ovulation. Progesterone tests are also used for the following:
- Monitoring your pregnancy
- Identifying the causes” of fertility issues
Doctors typically order serum progesterone tests for day 21 of your cycle.
Why is 21 the lucky number?
If you have regular 28-day cycles, ovulation should typically happen around day 14. This is when your ovaries release an egg. So, a week later (day 21), your progesterone levels should peak, hence day 21 for the blood test.
However, if you have a longer or shorter cycle length, day 21 testing may be inaccurate.
For instance, if you have a 32-day cycle, you’ll ovulate around day 18. Your progesterone levels should peak about 7 days later which would be day 25. So a progesterone test on day 21 won’t be accurate.
Know More: Day 21 Progesterone Testing: What it is & Why it’s Important
Ultimately, your doctor will order the right progesterone test for you if you’re struggling with ovulation due to a hormonal imbalance, PCOS, or irregular cycles.
Now how about PdG tests?
The best use for PdG tests is to confirm ovulation. A surge in PdG levels is a reliable marker to confirm ovulation. So if you are looking to conceive, PdG tests may be your new best friend!
Know More: PdG Test: Key Things To Know About Progesterone Tests
Urine vs. blood test
As you can imagine, a blood test and a urine test require different methods.
Take a look at this chart that illustrates the differences between the two tests:
Now that we have covered the differences between the blood and urine tests, let’s look at how to interpret your results!
How do you read progesterone and PdG test results?
Remember – your progesterone levels increase after ovulation. When you use these tests, look for an increase in your progesterone levels to confirm ovulation.
Note: Progesterone and PdG tests use different units and ranges. Blood progesterone is measured in ng/mL, while PdG is measured in ug/mL.
Here’s a look at how their values change based on your cycle:
Before ovulation
Blood progesterone levels: 0.1 – 0.7 ng/mL
Urine progesterone PdG levels: 0 – 3 ug/mL
After ovulation
1-6 DPO
You won’t see much change in your progesterone levels at this point. That’s because your progesterone is just beginning to slowly rise.
Blood progesterone levels: 0.1 – 0.7 ng/mL
Urine progesterone PdG levels: >5 ug/mL
7-10 DPO
If you’ve ovulated, your levels should increase during this time.
Blood progesterone: 2 – 25 ng/mL
Urine progesterone PdG: 6 – 40 ug/mL
If your levels are lower than these thresholds, then it’s likely that you haven’t ovulated.
11+ DPO
If you’re pregnant, you’ll see the biggest increase here. If you’re not pregnant, then your progesterone levels will drop.
Blood progesterone: >25 ng/mL if you’re pregnant.
Urine progesterone PdG: >40 ng/mL if you’re pregnant.
*Note: These ranges are probable; it’s possible to ovulate outside of the ranges provided.
Can I compare my serum progesterone levels with my PdG levels?
Blood progesterone tests are considered the gold standard and are the top choice for doctors. However, studies show a strong connection between the values of blood progesterone and PdG.
You can see in the following chart that blood progesterone levels and PdG levels correlate closely and reflect the same trend:
So, keep this in mind: Though the exact measurements vary, there is a strong correlation between PdG and blood progesterone.
This means you can rest assured that measuring your urine PdG levels is accurate for confirming ovulation!
Now that you’ve got that info, let’s look at the advantages of urine tests.
What are the advantages of urine hormone testing?
- Convenient
Urine tests can be done from the comfort of your own home on as many days as you want, which is great for convenience.
Blood tests require more time since you have to make an appointment with your doctor or a lab.
- Affordable
Urine tests are relatively cheap and easy to access.
Blood tests are more expensive because they require a healthcare provider or a nurse to administer the test, and then the lab to read the test. However, the price may vary according to your insurance plan. Reach out to your insurance provider to know the exact amount you’ll owe.
- Pain-free
Urine tests are pain-free. Just dip your strip into your urine and voila!
Blood tests aren’t extremely painful, but you do have to get a needle stick for a blood draw.
- Accurate
As mentioned above, studies show that urine progesterone tests are just as accurate as blood ones at confirming ovulation.
PdG testing with Inito
Now that we’ve covered the advantages of urine hormone testing, you might be wondering how you can test your levels.
That’s where the Inito Fertility Monitor comes in!
With Inito you can track PdG levels at home.? You’ll also get a chart of the actual values of your hormone that you can share with your doctor.
But that’s not all.
The Inito Fertility Monitor also tests FSH, LH, and estrogen to flag your fertile window and notify you when you’re about to ovulate. And, it tests the actual numerical values of all four hormones on a single test strip. Talk about convenience!
TL;DR
- Progesterone plays a key role in your menstrual cycle and pregnancy. It helps you confirm ovulation, preps the uterine lining for implantation, and supports pregnancy.
- PdG (pregnanediol glucuronide) is a urine metabolite of progesterone.
- Progesterone tests measure progesterone levels in the blood.
- PdG tests measure PdG levels in the urine.
- There is a close correlation between progesterone and PdG levels throughout your menstrual cycle. If your blood progesterone levels rise, so do PdG levels. Similarly, if your blood progesterone levels fall, you can see a similar trend in your PdG levels.
- Both serum progesterone tests and urine PdG tests can accurately confirm ovulation.
- PdG urine tests have advantages that blood tests don’t, including convenience, cost, and freedom from pain.
FAQs
A progesterone test shows your blood progesterone levels. The levels of this hormone need to be elevated (rises to 2 – 25 ng/mL) to confirm ovulation.
Progesterone is the hormone that shows up in your blood and PdG is the metabolite that shows up in your urine after progesterone has been processed in your body.
Yes! Studies show that PdG rises after ovulation and closely correlates with blood progesterone levels. That’s why it can be used to confirm ovulation.
It is pain-free, affordable, accurate, and doesn’t require going to the lab. You can do PdG tests at home!
No, they are different. A progesterone blood test measures the levels of progesterone in your blood, while a PdG urine test measures the level of PdG (a urine metabolite of progesterone).
Blood tests are typically used by doctors. But urine tests have proven to be equally as accurate in confirming ovulation and come with some great advantages, including:
-Convenience
-Affordability
-Freedom from pain
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- Physiology, Progesterone | NIH
- Progesterone | University of Rochester Medical Center
- Progesterone – Health Encyclopedia – University of Rochester Medical Center
- Neuroendocrine regulation of the corpus luteum in the human. Evidence for pulsatile progesterone secretion | NIH
- Monitoring the menstrual cycle: Comparison of urinary and serum reproductive hormones referenced to true ovulation | Green-ivf
