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Day 21 progesterone test – what does your level mean?

October 26, 2021, by Juliette Millar (BSc)

Day 21 Progesterone Blood Test Levels

[VIDEO]  So, you’ve been to see your doctor and you’ve had a Day 21 progesterone test done – to find out if you’re ovulating or not and perhaps to also see if your progesterone levels are high enough for getting pregnant.  

And now you’ve got your results back, and you’re wondering what they mean.  Is your progesterone too low?  Is it too high?  And what does it mean for your chances of pregnancy?  

In this article, I’m going to help you understand what YOUR progesterone levels mean, both for ovulation and for getting pregnant.  

But before we jump in, let’s do a quick Progesterone 101.  Why is progesterone so important and why would you get your levels of this hormone tested? 

Progesterone 101

Progesterone is one of the key female reproductive hormones.   It’s made mostly by your ovaries, but a small amount is also made by your adrenal glands and nervous system.

Progesterone is a wonderful hormone that does a number of very beneficial things in your body.  But its primary role is to prepare the lining of your uterus to receive and nurture an embryo and then to help maintain an ongoing pregnancy.  

Now the really important thing to know here is that your progesterone levels change significantly throughout your menstrual cycle.  And this change is completely dependent on ovulation.

Pregnant Belly 2

During the first part of your menstrual cycle, before you ovulate, you only have a tiny amount of progesterone in your bloodstream.  But after ovulation, your ovaries start making relatively LARGE amounts of this hormone.  And this increased level of progesterone can be detected in your blood.

Day 21 Progesterone Levels

So doing a Day 21 progesterone test (serum progesterone) can help your doctor figure out if you’re ovulating or not.  If your progesterone level stays low throughout your cycle, this indicates that you haven’t ovulated.  But if your progesterone level increases, beyond a certain threshold, this indicates that you have ovulated.  

In some cases, the test might also be used to get an idea if your progesterone level is high enough for successful implantation and pregnancy.

Beware – Important!

Blood test to check if woman ovulating

Now before I go any further, I want to make it really clear that’s it’s imperative you get your blood drawn on the CORRECT day of your menstrual cycle.  

If you get the test done on the WRONG day of your cycle, the results can end up being inconclusive or even worse, suggest you have a problem, even when you don’t!  

To find out how to do your Day 21 progesterone test the RIGHT way to ensure you get a meaningful result, check out the blog article below.

Day 21 Progesterone Test – Beware!

So, what do YOUR Day 21 progesterone test results mean?

What progesterone level confirms ovulation? 

Let’s start off with the progesterone level you’re looking for to confirm that you ARE ovulating.  
 
Now unfortunately, different laboratories often have different values for this, which can make things really confusing.  And this is partly because often the test isn’t timed well. 
 
But IF you HAVE timed your Day 21 progesterone test correctly, you can be confident you’ve ovulated if your progesterone level is 3 ng/ml (9.54 nmol/l) or above (depending on the units your particular lab uses).  If your level is below 3 ng/ml (9.54 nmol/L) this indicates that you probably haven’t ovulated, at least not in THAT particular menstrual cycle. 


Progesterone level for ovulation

≥ 3 ng/ml (9.54 nmol/l):   You have ovulated
< 3 ng/ml (9.54 nmol/l):   You probably haven’t ovulated (in that cycle)

But again, if your result suggests you haven’t ovulated, do make sure that you’ve timed your test correctly by checking out the blog article I mentioned earlier.  

What about the progesterone level needed for pregnancy?

OK, what about the level of progesterone that’s needed to support implantation and allow you to get pregnant.  How high does this need to be? 

You might have heard, that for successful implantation of an embryo and for pregnancy to occur, you need to have a progesterone level of at least 10 ng/ml (30 nmol/L).  This figure is mentioned a lot online and you might have even heard it from your doctor.

But if you know me, you’ll know it’s a goal of mine to give you the best, evidence-based information possible.  And when I looked into the scientific research on this, I wasn’t convinced that this figure is actually correct.  

Instead the true progesterone level needed for pregnancy is probably lower.

This value of 10 ng/ml (30 nmol/l) seems to have come from a study of women who were given a particular kind of fertility medication called hMG (human menopausal gonadotropin).  hMG can have the effect of increasing progesterone levels.  So if you’re NOT using hMG to conceive, the minimum value of progesterone identified in this particular study may NOT actually be appropriate.  

And another more recent study backs this up.  This 2018 study was carried out in women who WEREN’T using hMG, including some who were trying to conceive naturally.  And this study concluded that the minimum amount of progesterone that’s needed to get pregnant is actually only 5.6 ng/ml or around 18 nmol/l


Progesterone level required for pregnancy:

≥ 5.6 ng/ml (18 nmol/l):   According to a recent scientific study

But probably, the higher your progesterone levels, the better.   Some research suggests that progesterone levels do tend to be higher in pregnancy cycles compared to non-pregnancy cycles, and that a nice high progesterone level in the days following implantation is less likely to result in an early miscarriage. 

Basically though, no progesterone level can guarantee that you’ll get pregnant or guarantee that you won’t miscarry.  But a good, high level, a week or more after you’ve ovulated IS a good sign.

Progesterone levels fluctuate

Vials of blood for Day 21 progesterone test levels
 Now having said all of that, it’s REALLY important to keep in mind that progesterone levels fluctuate a HUGE amount over the course of a day.  In fact, they can fluctuate 8-fold in just 90 minutes!
 
So one single, lowish reading does NOT automatically mean there’s a problem.  It could just be that your blood was taken at a time when your progesterone was at a low point – and if you got it tested a second time there’s a good chance the next result could be much higher. 

What does a REALLY high progesterone level mean?

Finally, what does it mean if a Day 21 progesterone test comes back really REALLY high!?  In my experience, this can sometimes be an early sign of successful implantation and pregnancy.  

But it can ALSO mean, that you’ve released two eggs in that cycle rather than just one.  This is called a multiple ovulation. And if you’d like to know more about this, check out my blog article on this topic below.

Can you ovulate twice in a menstrual cycle?

Take home message

The Day 21 progesterone test can be very useful in helping you and your doctor figure out if you’re ovulating or not.  But it’s IMPERATIVE that the test is done the right way.

If the test is done at the correct time in your menstrual cycle, you can be confident you’re ovulating if your result is above 3 ng/ml (9.54 nmol/L).  And if the result is at least 5.6 ng/ml (18 nmol/l) and you’re not using hMG fertility medication to conceive, this is likely to be high enough for you to get pregnant.

But as always, if you’re concerned about your progesterone levels or you need more clarification, your doctor is the best person to talk to.

 

Related posts:

  1. Is a thyroid problem causing your infertility?
  2. Ovulation Calculator vs Fertility Charting – which is best?
  3. Best time to get pregnant – you might be surprised!
  4. How to tell if you’re ovulating – 2 easy ways to find out for sure!

Filed Under: Fertility Tests, General Fertility Info

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