Finasteride, Serum/Plasma — Qualitative Detection
This blood test detects whether finasteride, a prescription medicine for prostate enlargement and hair loss, is present in serum or plasma.
["The test can show whether finasteride is detectable in your blood."]
Key facts at a glance
- LOINC
- 73378-2
- Short code
- Finasteride ind plt IgM SerPl Ql FC
- Synonyms
- Finasteride ind plt IgM SerPl Ql FC
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- flow-cytometry
- CPT
- 84484
- SNOMED
- 302774002
- 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 this test?
This test looks for finasteride in a blood sample. Finasteride is a prescription medicine that blocks the production of dihydrotestosterone, a hormone involved in prostate enlargement and male-pattern hair loss. A qualitative result generally indicates whether finasteride was detected.
Why might I need this test?
A clinician may order this test to confirm recent exposure to finasteride, investigate an unexpected response to treatment, or assess medication use when adherence is uncertain. It may also be relevant when a drug interaction or an unintended exposure is suspected.
How is the test performed?
A blood sample is collected by venipuncture and separated into serum or plasma. A laboratory method then checks the sample for finasteride and reports whether the medicine was detected.
How do I prepare for the test?
Special preparation is usually not required, and fasting is generally unnecessary unless your clinician or laboratory gives different instructions. Continue taking finasteride as prescribed unless your clinician tells you otherwise, and be ready to provide the time and dose of your last dose.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A detected result indicates that finasteride was present in the sample at the time of testing, but it does not by itself show whether the dose or treatment schedule was correct. A result that is not detected does not necessarily mean the medicine was never taken because its presence depends on when the sample was collected and how long it remains detectable. Results should be interpreted alongside dose timing, symptoms, and other medications.
Short name
Finasteride blood test
Frequently asked questions
Does this test measure the effectiveness of finasteride?
Will I need to stop finasteride before the test?
How soon after taking finasteride can it be detected?
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 17, 2026. · Read our editorial policy