Progesterone is a blood test that measures progesterone levels in the blood. Normal range: Progesterone swings with the cycle: it is low in the follicular phase (under ~3 nmol/L) and rises after ovulation. A mid-luteal (day 21) level above ~30 nmol/L confirms that ovulation has occurred. Levels are very high in pregnancy. Because of this, the day of the cycle must be recorded.. It is commonly used to evaluates ovulatory function, reproductive health, and hormone balance in females..
What is Progesterone?
A hormone produced mainly by the ovaries that prepares the uterus for pregnancy.
Why is it measured?
Evaluates ovulatory function, reproductive health, and hormone balance in females.
Normal Reference Range
Progesterone swings with the cycle: it is low in the follicular phase (under ~3 nmol/L) and rises after ovulation. A mid-luteal (day 21) level above ~30 nmol/L confirms that ovulation has occurred. Levels are very high in pregnancy. Because of this, the day of the cycle must be recorded.
Note: Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation.
What Causes High PROGESTERONE?
High progesterone is normal in the luteal phase (after ovulation) and during pregnancy, where it rises progressively. Outside these, raised levels can be caused by an ovarian cyst, congenital adrenal hyperplasia, or, rarely, an ovarian or adrenal tumour. In fertility monitoring, an appropriately high day-21 progesterone is the desired result confirming ovulation.
What Causes Low PROGESTERONE?
Low progesterone in the luteal phase suggests ovulation did not occur (anovulation) or a luteal phase defect, both relevant causes of irregular cycles and difficulty conceiving. It is also naturally low after menopause and can be lowered by stress, significant weight changes, thyroid dysfunction and high prolactin. In early pregnancy, a low level may indicate a non-viable pregnancy.
How Often Should PROGESTERONE Be Tested?
For ovulation confirmation, progesterone is measured in the mid-luteal phase — about day 21 of a 28-day cycle, or 7 days before the expected period in longer cycles. It may be repeated over several cycles when investigating subfertility. In early pregnancy it is sometimes tracked alongside hCG.
Related Blood Markers
Progesterone is interpreted with oestradiol, LH and FSH across the cycle, and with hCG in early pregnancy. When cycles are irregular, prolactin, TSH and androgens (testosterone, DHEAS) are often checked too.
Key Facts
- •Category: Hormone Health
- •Unit of Measurement: nmol/L
- •Test Code: PROGESTERONE
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