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Free Prothrombin Fragment 1+2 (F1+2) in Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures the presence of small peptide fragments (F1+2) produced during blood clotting, which can help assess the activity of the coagulation system.

Quick summary

["F1+2 helps evaluate bleeding or clotting disorders by tracking early steps in blood clotting."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
59237-8
Short code
PSA Free MFr Plr
Synonyms
PSA Free MFr Plr
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Ref low
0
Ref high
4
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84153
SNOMED
39392002
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test if you have symptoms of bleeding disorders, such as excessive bruising, prolonged bleeding from cuts, or unexplained nosebleeds. It may also be used to monitor certain blood clotting conditions, like liver disease or anticoagulant therapy, or to check for inherited bleeding disorders like hemophilia.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into a vein in your arm to draw blood. If you’re on blood thinners, let your doctor know before the test.

How the Test Results Are Interpreted

Results are typically reported as a ratio or percentage compared to a standard. Higher levels may suggest abnormal clotting activation, while lower levels could indicate bleeding risks or liver issues.

Common Conditions Monitored

This test is often used to monitor patients with liver disease (e.g., cirrhosis), those on anticoagulants (like warfarin), or those with suspected inherited bleeding disorders.

Reference range

Normal: <4.0 ng/mLN/A

Specimen: fluid

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

F1+2 fragments are generated during the initial steps of blood clotting. Elevated levels may indicate hypercoagulable states (e.g., early clotting disorders), while decreased levels can signal bleeding risks or impaired liver function. It’s a useful marker for diagnosing or managing conditions affecting coagulation pathways.

Short name

F1+2 Test

Frequently asked questions

What does an abnormal F1+2 result mean?
An abnormal result doesn’t have a single interpretation—it depends on your symptoms, medical history, and other test results. For example, high levels might suggest an early clotting event, while low levels could indicate bleeding tendencies or liver problems. Your doctor will discuss this with you.
Can lifestyle changes affect F1+2 test results?
Generally, lifestyle factors like diet or exercise don’t directly impact F1+2 levels. However, conditions like liver disease or certain medications (e.g., blood thinners) can influence results. Always follow your doctor’s advice for test timing.
Is F1+2 the same as other clotting tests like PT/INR?
No, F1+2 measures specific peptide fragments in the clotting process, while PT/INR assesses overall clotting time using standardized reagents. Both are complementary—F1+2 gives insight into early clotting events, while PT/INR evaluates broader coagulation function.
  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 16, 2026. · Read our editorial policy