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Finasteride-Induced Platelet Immunoglobulin G (IgG) Antibody, Serum/Plasma — Qualitative

Published: August 9, 2026Updated: August 17, 2026

A qualitative test for finasteride-associated IgG antibodies on platelets, used when a drug-related immune platelet reaction is suspected.

Quick summary

["A positive result may support finasteride-related immune thrombocytopenia, but it must be interpreted with your blood count and medication history."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
73379-0
Short code
Finasteride ind plt IgG SerPl Ql FC
Synonyms
Finasteride ind plt IgG 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 is a specialized antibody test that checks for IgG attached to platelets in association with finasteride, a medicine used to treat an enlarged prostate and male pattern hair loss.

Why might I need this test?

Your clinician may order it if you develop a low platelet count, unusual bruising, or bleeding after starting finasteride and an immune-related drug reaction is suspected.

How is the test performed?

A blood sample is collected, and serum or plasma is separated for laboratory testing. The laboratory looks for finasteride-dependent platelet IgG using a validated antibody-detection method.

How do I prepare for the test?

No special preparation is usually required. Tell your clinician when you started or stopped finasteride and about all medicines and supplements you take; do not stop prescribed medication without medical advice.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Finasteride-induced platelet IgG antibody

Frequently asked questions

What does a positive result mean?
It means the laboratory detected IgG associated with platelets in a finasteride-dependent pattern. This can support an immune reaction to finasteride that affects platelet function or platelet count.
Does this test diagnose thrombocytopenia?
No. The test helps identify a possible immune cause; a complete blood count and other laboratory findings are needed to confirm thrombocytopenia.
Should I stop finasteride if the result is positive?
Contact the clinician who prescribed it before making any changes. The result should be reviewed in the context of your symptoms, platelet count, and overall health.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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