What is progesterone?
Progesterone is a steroid hormone initially secreted after ovulation by the corpus luteum, an area in the ovary which develops after ovulation. Prior to ovulation, progesterone levels are very low. They increase right after ovulation and reach levels above 10 ng/ml usually by 5-7 days after ovulation takes place. If you are not pregnant, progesterone levels usually decrease around the time of the next menstrual period bleeding.
What is a normal progesterone level?
Before ovulation, progesterone is well below 10ng/ml and after ovulation, it is well above 10ng/ml. The time right after ovulation until the next menstrual period is called the “corpus luteum phase” or the “luteal phase.” During the luteal phase, the fertilized egg travels through the fallopian tube into the uterus where it implants usually 6-12 days after fertilization. The normal luteal phase lasts on average 14 days, and it can be anywhere from 12 to 17 days long.
Pregnancy cannot be diagnosed by testing progesterone levels. Only the presence of the pregnancy hormone hCG diagnoses a pregnancy.
What does progesterone do?
Progesterone prepares the endometrium, the lining of the uterus, for implantation and a possible pregnancy. It prevents contractions of the uterus and the development of a new follicle, and during pregnancy, it is produced by the placenta and maintains the pregnancy until birth.
Can pregnancy be diagnosed from a progesterone level alone?
Progesterone levels normally rise during the first 36-38 weeks of the pregnancy, then fall towards the due date. Pregnancy cannot be diagnosed by testing progesterone levels. Only the presence of hCG the pregnancy hormone hCG diagnoses a pregnancy.
Can progesterone levels signal ovulation?
Progesterone levels are usually drawn about a week after presumed ovulation because they reach peak levels at that time. Drawing the blood too early may give false negative test results. A false negative progesterone level result means that you did ovulate but the blood was drawn too early and the progesterone level was falsely low. After ovulation, progesterone is produced increasingly from the corpus luteum and the progesterone levels gradually rise from a baseline of 1.5 to 3 ng/mL by the first day after ovulation. Levels then continue to rise until it reaches a peak 7 days after ovulation reaching levels of approximately 10-20 ng/mL. Progesterone levels can vary depending on the timing of the blood draw, and even on the same day can be very different.
What are normal progesterone levels test results before and during pregnancy?
Progesterone levels are only averages and they can change based on many variables. For example, the timing of the cycle, whether you ovulate or not, which lab tested them, whether blood is taken after you eat or before, and whether it's in the morning or afternoon, can all affect the outcome of a progesterone level test.
- Women at the beginning of their menstrual cycle: 1 ng/mL or under
- Before you ovulate, progesterone levels are usually below 10 ng/ml
- In the middle of the second half of the cycle, midcycle, about 7-10 days after ovulation, progesterone levels are usually above 8-10 ng/ml.
- Women in the middle of their menstrual cycle: 5 to 20 ng/mL
- First-trimester pregnancy: 11.2 to 90 ng/mL
- Second trimester pregnancy: 25.6 to 89.4 ng/mL
- Third-trimester pregnancy: 48.4 to 42.5 ng/mL
- Progesterone levels are usually higher when you are pregnant, but even in a non-pregnant patient, they can reach 20 ng/ml. In a pregnancy cycle, they should be greater than 10 to 12 ng/ml to have a better chance of a good pregnancy outcome.
What can you do for low progesterone levels?
A low progesterone level especially a level below 10 ng/ml may mean that you did not ovulate. If you did ovulate, there are many different opinions as to what to do if the levels are low. Some doctors give progesterone (pills, shots, suppositories) and others don't treat unless there has been some proof of a pre-existing low progesterone in non-pregnancy cycles.
Can a low progesterone level predict an ectopic pregnancy?
According to a study done by Buckley and colleagues (Ann Emerg Med 2000 Aug;36(2):95-100), all patients with an ectopic pregnancy had a progesterone level below 22 ng/ml. Of the patients with a progesterone level below 22 ng/ml, 10% had an ectopic pregnancy, but none of the patients with progesterone over 22 had an ectopic pregnancy. Of the patients who did not have an ectopic pregnancy, 73% had a progesterone level below 22 ng/ml. This means that if your progesterone level is above 22 ng/ml, your chances of having an ectopic pregnancy according to this study was 2% or less. But even if your progesterone level is below 22 ng/ml, your chances of NOT having an ectopic is above 88%.
What is a false positive progesterone level?
The two main reasons for an elevated progesterone level are ovulation and pregnancy. Other than after ovulation or pregnancy, progesterone levels can also be elevated by the following:
- Laboratory error due to cross-reactivity with other hormones
- Taking progesterone pills or suppositories
- Ovarian cancer
- Adrenal cancer
- Congenital adrenal hyperplasia, a group of disorders that affect your adrenal gland