Lab marker · High

High Antithrombin III: what it means

A Antithrombin III result above the normal range is considered high. Here is what a raised Antithrombin III can point to, and when it is worth discussing with a doctor.

Reference range: ~80–120% of normal activity; a natural anticoagulant that keeps clotting in check — a LOW level (deficiency) is a thrombophilia, raising the risk of abnormal blood clots (thrombosis)

Understand your full result

What a high Antithrombin III can mean

  • A normal or high antithrombin level is reassuring — it does not indicate a clotting problem.
  • A high level has no adverse clinical significance.

When to discuss with a doctor

Antithrombin is a specialist test, part of a thrombophilia work-up rather than a routine check. It is measured mainly when someone has had a blood clot that is unexplained, unusually severe, recurrent, in an unusual site, or at a young age, or when there is a strong family history — to look for an inherited tendency to clot. A confirmed antithrombin deficiency influences how a clot is treated and prevented, decisions about longer-term anticoagulation, and guidance for family members. Because an acute clot and blood thinners themselves lower the level, timing and interpretation are important and best handled by a haematologist. Mediora.AI shows antithrombin alongside protein C, protein S and D-dimer so the thrombophilia pattern is read together; confirming and acting on a deficiency belongs with your doctor or haematologist.

Conditions this can relate to

Keep reading

One value is a snapshot. Upload the full test to see every marker explained together.

Upload your test - free

Mediora.AI is informational - interpretation, not a diagnosis. A single out-of-range value is common and often benign; always discuss decisions with your doctor.