Serum or plasma concentration of free (unbound) progesterone
This test measures the amount of progesterone in your blood that is not attached to proteins, providing a more accurate reflection of biologically active progesterone levels.
["Free progesterone helps regulate your menstrual cycle and pregnancy."]
Key facts at a glance
- LOINC
- 39911-3
- Short code
- Deprecated Hrt RI FP+WM+EF V1 W RNC IV
- Synonyms
- Deprecated Hrt RI FP+WM+EF V1 W RNC IV
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- radnuc
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Is Free Progesterone Used For?
Free progesterone testing is often used to assess reproductive health, diagnose hormonal imbalances, or evaluate fertility. It can help identify issues like luteal phase deficiency, ovarian dysfunction, or hormonal disorders that may affect menstrual cycles or pregnancy.
When Might You Need This Test?
Your healthcare provider may recommend a free progesterone test if you have irregular periods, trouble conceiving, symptoms of hormonal imbalances (such as heavy bleeding or missed periods), or if you’re undergoing fertility treatments.
How Is the Test Performed?
A blood sample is drawn from a vein, usually in your arm. The sample is then processed to separate serum or plasma, where the free progesterone level is measured using a specialized immunoassay technique.
What Does a Low or High Level Mean?
Low free progesterone levels may suggest problems with ovulation or luteal phase insufficiency, which can affect fertility. High levels might indicate conditions like polycystic ovary syndrome (PCOS) or certain hormonal tumors, though further evaluation is needed.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical significance: Free progesterone is critical for maintaining early pregnancy and supporting the luteal phase of the menstrual cycle. Abnormal levels can point to underlying reproductive health concerns that may require medical intervention or further testing.
Short name
Free Progesterone
Frequently asked questions
Why is my free progesterone test result different from what I expected?
Does free progesterone testing hurt?
Can I eat or drink before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy