The next time your doctor orders a progesterone test, ask yourself: “When is the right day to do this test?”
Forget “day 21 progesterone.” There’s no reason to test progesterone until you are approximately one week before your period. That will depend on how long your cycle actually is.
Here’s what you need to know about progesterone testing.
The brief window of progesterone
You make progesterone only during the ten to fourteen days following ovulation—the ten to fourteen days before your period. That’s your luteal phase. You cannot expect to see any progesterone before then.
If you have a longer cycle, you will have almost no progesterone for most of your menstrual cycle, and that’s normal.
You want to try to test progesterone at its highest point, which is about halfway through the luteal phase. In other words, the best testing day is five to seven days after ovulation and five to seven days before the period.
If your cycles are regular, identify the date of your next expected period, and then count seven days before that. For example:
- With a 21-day cycle, test progesterone on approximately day 14
- With a 28-day cycle, test progesterone on approximately day 21
- With a 35-day cycle, test progesterone on approximately day 28
👉 Tip: Day 1 is the first day of proper menstrual flow. Days of pre-period light flow or spotting count as the final days of your previous cycle.
If your cycles are irregular, it’s harder to know when to test. The best plan is to detect ovulation and then count five to seven days.
How to detect ovulation
- Watch for fertile mucus and twinges in your pelvis. When you see these physical signs of possible ovulation, count five to seven days, and then have the blood test.
- Test with LH ovulation test strips. Start testing your urine a few days before you think you’ll ovulate. When you see the double line indicating LH surge, count five to seven days, and then have the blood test.
👉 Caution: You cannot rely on ovulation test strips if you have PCOS because your LH could be chronically elevated.
- Chart your basal body temperature (BBT). Using an ovulation thermometer, take your early morning resting temperature. You will see it rise 0.5℃ (0.9℉) after ovulation. When you see your temperature rise, count five to seven days from the start of the rise, and then have the blood test.
👉 Tip: BBT charting is a great way to confirm ovulation and progesterone, even without a blood test.
Check in with your actual period
Don’t interpret your progesterone result until your period has actually arrived. Wait for your period, and then ask: “Was the test done within 14 days before my period?”
If not, then it is not a valid test and cannot be used to diagnose progesterone deficiency or estrogen dominance.
👉 Tip: If you’re certain you ovulated, but your period does not come within fourteen days, you could be pregnant, so do a pregnancy test!
When it’s normal to have no progesterone
There are three situations in which you can expect no progesterone, so there’s no point in testing.
- You’re in your follicular phase. And remember: if you have long cycles, your follicular phase is many weeks long—most of your cycle.
- Hormonal birth control. Almost all types of hormonal birth control switch off progesterone. The only exception is the hormonal IUD (Mirena or Skyla), which permits ovulation some of the time in some women (usually older women).
- Post-menopause. Unless you take body-identical progesterone, you will have no progesterone after menopause. And if you take body-identical progesterone (Prometrium or Utrogestan), your serum levels should not exceed the baseline level of 1.8 ng/mL (5.5 nmol/L).
Interpreting your progesterone result
To confirm ovulation: Serum progesterone above 4 ng/mL (13 nmol/L) confirms ovulation. If it’s less than that (and the timing was correct), it means you did not ovulate. Instead, you had an anovulatory (non-ovulation) cycle.
Anovulatory cycles are common with polycystic ovary syndrome or PCOS. Your strategy is to correct the underlying reason for PCOS so you can start to ovulate again and make progesterone.
👉 Tip: These reference ranges are for progesterone on a blood test. I don’t recommend saliva or urine to assess progesterone.
To assess optimal progesterone: The optimal range of progesterone is greater than 8 ng/mL (25 nmol/L), and the higher the better. But don’t worry too much if your result is at the low end of normal. Progesterone fluctuates every ninety minutes, so a low-normal reading may simply mean the blood was drawn at a low point. It’s not possible to have “too much” endogenous (made by the body) progesterone.
Ask me in the comments.
