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Also known as: Fragment D-dimer; fibrin degradation fragment
Formal name: D-dimer

At a Glance

Why Get Tested?

To help diagnose or rule out thrombotic (blood clot-producing) diseases and conditions

When to Get Tested?

When you have symptoms of a disease or condition that causes acute and/or chronic inappropriate blood clot formation such as: DVT (deep vein thrombosis), PE (pulmonary embolism), or DIC (disseminated intravascular coagulation), and to monitor the progress and treatment of DIC and other thrombotic conditions

Sample Required?

A blood sample drawn from a vein in your arm or sometimes from a finger stick (a blood sample drawn from the fingertip)

The Test Sample

What is being tested?

When a vein or artery is injured and begins to leak blood, a sequence of clotting steps and factors (called the coagulation cascade) is activated by the body to limit the bleeding and create a blood clot to plug the hole. During this process, threads of a protein called fibrin are produced. These threads are crosslinked (glued together) to form a fibrin net that catches platelets and helps hold the forming blood clot together at the site of the injury.

Once the area has had time to heal, the body uses a protein called plasmin to break the clot (thrombus) into small pieces so that it can be removed. The fragments of the disintegrating fibrin in the clot are called fibrin degradation products (FDP). One of the FDPs produced is D-dimer, which consists of variously sized pieces of crosslinked fibrin. D-dimer is normally undetectable in the blood and is produced only after a clot has formed and is in the process of being broken down. Measurement of D-dimer can tell your doctor that something has increased the body's clotting mechanisms above its normal limits.

How is the sample collected for testing?

Typically, a blood sample is drawn from a vein in your arm. As an alternative, particularly in pediatric care, the blood sample is drawn from the fingertip.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.