Next time your doctor orders a progesterone test, please stop for a minute, and ask yourself: “When is the right day to do this test?”
Of course, you’d hope your doctor would ask herself the same question, and then guide you to the correct day. But if your doctor is like other family doctors, she has surprisingly little knowledge of the female hormone cycle. She may not know when to test.
Your brief window of progesterone
You make progesterone for just a brief 10-14 days after ovulation, which is the 10-14 before your period. That’s your luteal phase. It doesn’t matter how long your cycle turns out to be. Your luteal phase is the final 10-14 days leading up to your period. You cannot expect to see any progesterone before then.
Test progesterone when it’s highest, which is about halfway through your luteal phase. It’s when you are 5-7 days after ovulation, and 5-7 days before your period.
If your cycles are regular, it’s pretty easy to figure out. Simply identify the date of your next expected period, and then count 7 days before. For example:
- 21-day cycle: Test progesterone on approximately day 14
- 28-day cycle: Test progesterone on approximately day 21
- 35-day cycle: Test progesterone on approximately day 28
⚠️ Tip: Day 1 of your cycle is the first day of real, heavy menstrual flow. Days of pre-period light flow or “spotting” are counted as the final days of your previous cycle.
If your cycles are not regular, it’s a bit trickier. The best plan is to try to detect ovulation and then count 7 days after. There are three ways to it:
- Watch for fertile mucus and twinges in your pelvis. When you see these physical signs of possible ovulation, count 5-7 days later, and then have the blood test. (Physical signs suggest ovulation, but they do not confirm it.)
- 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 5-7 days later, and then have the blood test.
- 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 4-6 days later, and then have the blood test. BBT charting is a way to confirm ovulation, and also a great way to assess progesterone all on its own! (Without a blood test.)
⚠️ Caution: If you suffer PCOS, you may have chronically elevated LH, and so cannot rely on ovulation test strips.
A final “accuracy 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 luteal phase test, and it cannot be used to diagnose progesterone deficiency or estrogen dominance (Read: Why I Don’t Use the Term Estrogen Dominance).
⚠️ Tip: If you’re certain you ovulated, but your period does not come within 14 days — do a pregnancy test!
The “no-progesterone zone”
There are three situations in which there’s no point testing progesterone because you can be certain you have none.
- Pre-ovulation (follicular phase). And remember: if you have long cycles, your follicular phase is many weeks long—the majority 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 some ovulation (but not regular ovulation).
- Post-menopause. Unless you take bioidentical progesterone, you will have almost no progesterone after menopause.
Interpreting your progesterone result
To confirm ovulation: If your serum mid-luteal progesterone is less than 1.8 ng/mL (5.5 nmol/L), then you did not ovulate. Instead, you had what is called an anovulatory (non-ovulation) cycle, which is a problem. Anovulatory cycles are common with polycystic ovarian syndrome or PCOS. Your strategy is to correct the underlying reason for PCOS, and therefore start to ovulate again. That’s how you’ll make progesterone.
⚠️ Tip: These reference ranges are for progesterone serum or blood tests. I don’t use saliva testing to assess mid-luteal progesterone.
To assess optimal progesterone: You want your serum mid-luteal progesterone to be greater than 8 ng/mL or 25 nmol/L, and the higher the better. (Read: The 7 Superpowers of Progesterone.) But don’t panic if your result is at the low end of normal. Progesterone fluctuates widely over the course of ninety minutes, so a low-normal reading may simply mean the blood was drawn at a low point.
⚠️ Tip: The best way to assess “optimal progesterone” is to chart basal body temperature (see above).
To check the safety of bioidentical progesterone: In general, the only reason to test progesterone during supplementation is to check if you’re getting too much. Take a few days off the cream or capsules before you test. If you’re post-menopausal, your serum reading should stay at the follicular phase level (less than 1.8 ng/mL or 5.5 nmol/L). You’re certainly not aiming for luteal phase levels! If you’re using a progesterone cream, your salivary reading could go quite high, but that’s usually transient. We can discuss post-replacement testing more in the comments.
What is your experience with progesterone testing? Please comment.