The next time your doctor orders a progesterone test, ask yourself: “When is the right day to take this test?”
Forget “day 21 progesterone.” There is no reason to try progesterone until about a week before your period. That depends on how long your cycle is.
Here’s what you need to know about progesterone testing.
The short window of progesterone
You make progesterone only within ten to fourteen days following ovulation—the ten to fourteen days before your period. That’s your luteal phase. You can’t expect to see any progesterone before that.
If you have longer cycles, you will have almost no progesterone for most of your menstrual cycle, and that is 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 days to test are five to seven days after ovulation and five to seven days before menstruation.
If your cycles are regulardetermine the date of your next expected period, and then count seven days before already. Example:
- In a 21-day cycle, try progesterone on approximately day 14
- In a 28-day cycle, try progesterone on approximately day 21
- In a 35-day cycle, try progesterone at approximately day 28
👉 Tip: The first day is the first day of proper menstrual flow. The days of pre-period light flow or spotting are counted as the last days of your previous cycle.
If your cycles are irregular, it’s harder to know when to try. The best plan is detect ovulation and then count five to seven days.
How to determine 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 get a blood test.
- Examination with LH ovulation test strips. Start testing your urine a few days before you think you will ovulate. When you see the double line indicating the LH surge, count five to seven days, and then get a blood test.
👉 Precautions: You can’t rely on ovulation test strips if you have PCOS because your LH can be chronically elevated.
- Chart your basal body temperature (BBT). Using an ovulation thermometer, take your morning resting temperature. You will see it rise by 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 get a 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
Do not interpret your progesterone result until your period actually arrives. Wait for your period, and then ask: “Was the test done within 14 days before my period?”
Otherwise, it is no a valid test and cannot be used to diagnose progesterone deficiency or estrogen dominance.
👉 Tip: If you’re sure you ovulated, but your period doesn’t come for fourteen days, you could be pregnant, so take a pregnancy test!
When there is no progesterone normally
There are three situations where you can expect no progesterone, so there is no point in testing.
- You are in your follicular phase. And remember: if you have a long cycle, your follicular phase is several weeks long—most of your cycle.
- Hormonal birth control. Almost all types of hormonal birth control kill progesterone. The only exception is the hormonal IUD (Mirena or Skyla), which allows ovulation sometimes in some women (usually older women).
- Post-menopause. Unless you take body-identical progesterone, you will have no progesterone after menopause. And if you are taking body-identical progesterone (Prometrium or Utrogestan), your serum level should not exceed the baseline level of 1.8 ng/mL (5.5 nmol/L).
Interpreting your progesterone result
To confirm ovulation: Serum progesterone greater than 4 ng/mL (13 nmol/L) confirms ovulation. If it’s less than that (and the timing is right), it means you not ovulating. Instead, you had an anovulatory (non-ovulation) cycle.
Anovulatory cycles are common in polycystic ovary syndrome or PCOS. Your strategy is to correct the underlying cause of PCOS so you can start ovulating and producing progesterone again.
👉 Tip: These reference ranges are for progesterone in the blood test. I do not recommend saliva or urine to test for progesterone.
To assess optimal progesterone: The optimal progesterone range is greater than 8 ng/mL (25 nmol/L), and higher is better. But don’t worry too much if your result is on the low end of normal. Progesterone changes every ninety minutes, so a low-normal reading may simply mean that blood is drawn at a low point. It is not possible to have “too much” endogenous (made by the body) progesterone.
Ask me in the comments.
