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Activated Partial Thromboplastin Time
Abbreviation: aPTT
Panel: Blood Clotting (Coagulation) · All clotting tests
Typical adult reference range
| Conventional units | 25–35 sec |
| SI units | 25–35 sec |
Ranges vary between laboratories and methods — compare your result with the range printed on your own report.
What a high or low result can mean
High activated partial thromboplastin time: prolonged values can be seen with heparin use, factor deficiencies, and lupus anticoagulant.
Low activated partial thromboplastin time: short values are not usually clinically significant.
These are associations, not a diagnosis: the same result can have several causes, and your clinician interprets it with the rest of your results and history.
Good to know
Normal ranges vary between laboratories and reagents.
Related tests — Blood Clotting (Coagulation)
Please note: Reference ranges vary between laboratories, and between the methods and instruments they use — the range printed on your own report is the one your result should be compared with. A result outside the range is not by itself a diagnosis, and a result inside it does not rule out illness. These pages are an educational summary, not medical advice: always discuss your results with the clinician who ordered them, who can interpret them in the context of your health and history.