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Free Prothrombin Fragment 1+2 (F1+2)

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

This test measures the presence of small peptide fragments released during blood clotting, which can help assess how well your blood is forming clots.

Quick summary

["Helps evaluate bleeding disorders and anticoagulant therapy effectiveness."]

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

Key facts at a glance

LOINC
59236-0
Short code
PSA Free MFr Prt
Synonyms
PSA Free MFr Prt
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
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
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 This Test Measures

Free prothrombin fragments (F1+2) are byproducts of the coagulation process. Normally, these fragments are present in small amounts, but elevated levels may indicate abnormal clotting activity or anticoagulant medication use.

Why It’s Ordered

Your healthcare provider may order this test if you have symptoms of bleeding disorders (like excessive bruising or nosebleeds), if you’re on blood thinners (like warfarin), or if you have conditions affecting blood clotting.

Common Conditions Monitored

High levels of F1+2 can suggest overactivation of clotting (thrombosis) or improper anticoagulant dosing. Low levels may indicate bleeding risks or clotting disorders.

How the Test Works

Blood is drawn and analyzed using a sensitive immunoassay method to detect the specific fragments. This helps track clotting processes without relying on traditional clotting times.

Reference range

Normal: <4.0 ng/mLN/A

Specimen: serum

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.

Elevated F1+2 levels may indicate hypercoagulability (increased clot formation), which can occur in conditions like disseminated intravascular coagulation (DIC) or after trauma. Conversely, low levels may signal bleeding tendencies or anticoagulant overdose. This test supports monitoring of anticoagulant therapy and diagnosing clotting disorders.

Short name

Free Prothrombin Fragments 1+2

Frequently asked questions

What does a high or low result mean?
A high result may suggest your body is producing too many clots or that your blood thinner is not working as intended. A low result could indicate bleeding risks or an issue with how your blood clots normally.
Does this test require fasting?
No fasting is required for this test. You can eat and drink normally before your blood draw.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time.
  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