What is the Thrombin Time test?

The Thrombin Time (TT) test is a coagulation blood test that evaluates the final step of the clotting process—conversion of fibrinogen into fibrin. In the laboratory, thrombin is added to plasma and the time taken for a clot to form is measured.

Unlike other clotting tests, TT specifically reflects fibrinogen quantity and function and is highly sensitive to substances that interfere with fibrin formation, such as heparin. It is commonly used alongside other coagulation tests to investigate abnormal bleeding or clotting.

Why do I need a Thrombin Time test?

An abnormal Thrombin Time can indicate problems with fibrinogen or the presence of anticoagulants that affect clot formation. It is particularly helpful when other coagulation tests are abnormal or when bleeding risk needs clarification.

You may need this test if you have:

• Unexplained or excessive bleeding
• Easy bruising
• Prolonged bleeding after surgery or dental work
• Suspected fibrinogen deficiency or dysfunction
• Liver disease affecting clotting factors
• Suspected heparin contamination or exposure
• Abnormal results on other coagulation tests

The test helps narrow down the cause of clotting abnormalities and supports further haematological assessment.

Benefits of the test

1. Assesses final clot formation step
   Focuses specifically on fibrin formation.
2. Sensitive to fibrinogen disorders
   Helps identify low or abnormal fibrinogen.
3. Detects anticoagulant interference
   Highly sensitive to heparin and similar agents.
4. Supports bleeding disorder investigation
   Useful when bleeding tendency is unexplained.
5. Complements other coagulation tests
   Adds clarity alongside PT and APTT.
6. Simple and rapid analysis
   Requires only a blood sample.
7. Useful in liver disease assessment
   Liver dysfunction can affect fibrinogen levels.
8. Objective laboratory measurement
   Provides clear, time-based results.

Step-by-step: How we offer testing

Clinic-based testing (UK-wide)

• Choose your nearest UK clinic
• Attend your appointment
• A clinician draws a blood sample
• Sample is sent to the laboratory
• Results are issued once analysis is complete

Home or hotel visit (+£60, UK-wide)

• Book a mobile phlebotomist
• Blood sample taken at your home or hotel
• No need to attend a clinic
• Sample securely transported to the laboratory

Your results explained

Shortened thrombin time (uncommon)

• Clot forms faster than expected
• UK standard: Below lab reference range (typically <14 seconds)
• May occur with elevated fibrinogen levels

Normal thrombin time

• Clot forms within expected time
• UK standard: Typically 14–21 seconds
• Suggests normal fibrinogen function

Prolonged thrombin time

• Delayed clot formation
• UK standard: >21 seconds
• May indicate low or abnormal fibrinogen, heparin presence, or inhibitors affecting clotting