High Activated Partial Thromboplastin Time (aPTT): what it means
A Activated Partial Thromboplastin Time (aPTT) result above the normal range is considered high. Here is what a raised Activated Partial Thromboplastin Time (aPTT) can point to, and when it is worth discussing with a doctor.
Reference range: 25–35 seconds (assay-dependent)
Understand your full resultWhat a high Activated Partial Thromboplastin Time (aPTT) can mean
- Unfractionated heparin therapy — expected and therapeutic.
- Haemophilia A (factor VIII deficiency) or B (factor IX deficiency) — congenital; usually known by adulthood but mild cases present late.
- Von Willebrand disease — commonest inherited bleeding disorder; mucocutaneous bleeding pattern.
- Lupus anticoagulant — paradoxically prolongs aPTT in vitro but causes thrombosis in vivo.
- Severe liver disease — failing factor synthesis affects both PT and aPTT.
- Vitamin K deficiency — late finding; PT/INR usually prolongs first.
- Disseminated intravascular coagulation (DIC) — consumed factors.
When to discuss with a doctor
aPTT is rarely a stand-alone test for patients to interpret. In the bleeding-disorder context, a prolonged aPTT with normal PT and normal platelets warrants haematology evaluation for von Willebrand disease, haemophilia or lupus anticoagulant. In a heparinised patient the value belongs to the medical team adjusting the infusion rate. Mediora.AI shows aPTT alongside INR, platelets and fibrinogen for the full coagulation picture.
Conditions this can relate to
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Upload your test - freeMediora.AI is informational - interpretation, not a diagnosis. A single out-of-range value is common and often benign; always discuss decisions with your doctor.