Progesterone: A Woman's Hormone Guide

What is progesterone

Progesterone is a steroid hormone produced mainly by the ovarian corpus luteum after ovulation. It prepares the uterine lining for embryo implantation and supports pregnancy. In men, the adrenal glands and testes produce small amounts of progesterone, but it is clinically tested far less often.

Blood progesterone levels vary depending on the phase of the menstrual cycle, so a result can only be interpreted when the day of the cycle on which blood was drawn is known.

Reference ranges

Progesterone norms depend strongly on the cycle phase and the laboratory method used. Indicative ranges (ng/mL):

• Follicular phase (cycle days 1–14): 0.1–0.9 ng/mL
• Luteal phase (cycle days 15–28): 2–25 ng/mL
• Ovulation confirmation: progesterone above 3 ng/mL in the luteal phase indicates ovulation occurred
• Pregnancy (1st trimester): 11–44 ng/mL
• Postmenopause: below 0.2 ng/mL

The laboratory's own reference range is always most important — the ranges listed depend on the method used.

Why progesterone may be low

Low progesterone in the luteal phase may indicate anovulation (ovulation did not occur) or a luteal phase defect. This is a common cause of infertility or early miscarriage. Other possible causes include polycystic ovary syndrome (PCOS), stress-related amenorrhea (due to intense exercise, high stress, or low body weight), hyperprolactinemia, and the perimenopause period.

Hormonal contraception suppresses natural progesterone production, so it is important to inform your doctor about any medications being taken at the time of testing.

Why progesterone may be high

High progesterone most commonly indicates pregnancy or the luteal phase of the cycle — this is a physiological norm. Pathologically elevated progesterone may be associated with congenital adrenal hyperplasia, ovarian cysts, or rare progesterone-producing tumors.

If progesterone is high in the follicular phase, this may indicate an early cycle ovulation disorder or a laboratory error.

What to do next

When investigating infertility or menstrual cycle disorders, a doctor often recommends a progesterone test on day 21 of the cycle (or 7 days after expected ovulation). A single low progesterone result does not always require treatment — sometimes it is sufficient to repeat the test in the next cycle.

If you are planning a pregnancy and progesterone is consistently low, your doctor may discuss progesterone supplementation.

Monitoring over time

Tracking progesterone changes over several cycles helps to better understand ovulation regularity. QbiLabs allows you to mark the cycle day and monitor how progesterone changes — this is useful both when planning a pregnancy and when assessing hormonal balance during perimenopause.

Questions for your doctor

1. Does my progesterone level indicate that ovulation occurred? 2. Should the test be repeated in the next cycle for a more accurate assessment? 3. Could my menstrual cycle disorders be related to a progesterone deficiency? 4. Should I also test other hormones (LH, FSH, estradiol) alongside progesterone?

*This is not medical advice. Consult a doctor for any health-related decisions.*