Skip to content

Thrombin Time (with Thrombin Addition) – Plasma

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

This test measures how long it takes for blood plasma to clot after adding a specific substance called thrombin. It helps assess blood clotting function, particularly the activity of clotting factors like fibrinogen.

Quick summary

["Checks how efficiently your blood can form clots under controlled conditions."]

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

Key facts at a glance

LOINC
86997-4
Short code
Guided Throm inf add day W throm in cath
Synonyms
Guided Throm inf add day W throm in cath
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
imaging-modality
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

Thrombin Time (TT) with Thrombin Addition evaluates the time it takes for plasma to clot after thrombin is added. Thrombin is an enzyme that converts fibrinogen (a protein in blood) into fibrin, which forms the structural framework of clots. This test is primarily used to screen for abnormalities in the intrinsic and common pathways of coagulation, including potential deficiencies in fibrinogen or other clotting factors.

Why It’s Done

This test may be ordered if you have symptoms of bleeding disorders (e.g., excessive bruising, prolonged bleeding from cuts) or if you’re undergoing treatment that affects blood clotting, such as anticoagulant medications. It can also help diagnose conditions like liver disease (which affects clotting factor production) or inherited clotting disorders.

How the Test Works

A small sample of your blood is collected and separated into plasma (the liquid part without clotting factors). Thrombin is then added to the plasma, and the time until a visible clot forms is measured. A longer clotting time may indicate reduced fibrinogen or other clotting factor activity, while a shorter time may suggest clotting factor overactivity or interference.

Preparation and Sample Collection

No special preparation is needed, but inform your healthcare provider about any medications (e.g., blood thinners) or medical conditions you have. Blood is drawn from a vein in your arm, and the plasma is analyzed immediately or stored for testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Thrombin Time (TT) with Thrombin Addition

Frequently asked questions

What does a prolonged thrombin time mean?
A prolonged thrombin time may suggest a deficiency in fibrinogen or other clotting factors, liver disease, or certain medications that interfere with clotting. It can also be seen in conditions like disseminated intravascular coagulation (DIC), where clotting and bleeding occur simultaneously.
What does a normal thrombin time indicate?
A normal thrombin time typically means your blood clotting mechanism is functioning as expected, though it doesn’t rule out other clotting disorders. It’s often used as a baseline or follow-up test alongside other coagulation studies.
Can this test be affected by diet or lifestyle?
No specific diet or lifestyle changes are required for this test, as it focuses on clotting factors present in your blood. However, avoid strenuous activity or excessive hydration 24 hours before testing to ensure accurate results.
  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