Coagulation Panel: what is included

In shortA coagulation panel is a set of tests about blood clotting: INR reflects the extrinsic pathway and steers warfarin dosing (typically 0.8–1.1 without anticoagulants), APTT times the intrinsic pathway (usually 25–35 seconds), fibrinogen is the clot's raw material (2.0–4.0 g/L (200–400 mg/dL)), and D-dimer is the trace of a dissolved clot. Blood is drawn from a vein into a citrate tube. The panel is ordered before surgery, for unexplained bleeding, and during anticoagulant therapy.

What this panel covers

The coagulation panel gathers the key links of the clotting system into one report. INR — the recalculated prothrombin time — gauges the extrinsic pathway and is the world standard for warfarin control. APTT measures the intrinsic pathway in seconds and uncovers factor deficiencies, including haemophilia.

Fibrinogen is the protein a clot is built from and an inflammation marker at the same time: it rises after surgery, with infections, and in pregnancy. D-dimer is a fibrin breakdown product: a negative result at low clinical probability lets the doctor rule out thrombosis without imaging. The platelet count from the CBC completes the picture with the first link of clotting.

Markers on the panel

INR aPTT Fibrinogen D-dimer Platelets (PLT)Antithrombin III Prothrombin time Thrombin time Lupus anticoagulant

Why it is ordered

The panel is ordered before planned operations and deliveries, for unexplained bruising or bleeding, after thrombosis, and to dose anticoagulants. People on warfarin test INR regularly — the dose depends on the result. Testing "blood thickness" without an indication is pointless: isolated numbers without a clinical question say almost nothing.

How to prepare

Morning, fasting, from a vein into a citrate tube filled exactly to the mark — an underfilled tube distorts the result. Tell the laboratory about every medication: anticoagulants change INR and APTT by design. For trend monitoring, use one laboratory — reagents differ.

How to read the report

Read the panel only as a whole: a prolonged APTT with a normal INR points toward intrinsic-pathway factors, while both rising together suggests liver trouble or vitamin K deficiency. A moderately high fibrinogen during inflammation is an expected finding, and a D-dimer above the reference without symptoms is nonspecific. Below, each marker is covered individually: ranges, causes of deviation, and preparation.

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Frequently asked questions

What does a coagulation panel include?

The minimum is INR (prothrombin time), APTT, and fibrinogen; D-dimer and platelets are often added. The set depends on the task: preoperative screening and warfarin control use different combinations.

Can the panel show whether blood is "too thick"?

Loosely, yes, though doctors avoid that phrasing. A clotting tendency shows as a pattern: short APTT, high fibrinogen, raised D-dimer plus clinical signs. A single number proves nothing.

Why is INR tested so often on warfarin?

Because the warfarin dose is chosen by INR: below target the clot risk grows, above it the bleeding risk. Early in therapy control is weekly; once stable, every few weeks on the doctor's schedule.

Sources

PT and INR: MedlinePlus Medical Encyclopedia — MedlinePlus, National Library of Medicine. Accessed: August 31, 2026.
Partial Thromboplastin Time (PTT): MedlinePlus Medical Encyclopedia — MedlinePlus, National Library of Medicine. Accessed: August 31, 2026.
Fibrinogen Blood Test: MedlinePlus Medical Encyclopedia — MedlinePlus, National Library of Medicine. Accessed: August 31, 2026.