Coagulation
aPTT
LOINC 14979-9 · s
Ranges
Reference range: 25–35 s
What it is
aPTT (activated partial thromboplastin time) measures how long part of your blood-clotting process takes to form a clot.
Why it matters
It helps check for bleeding or clotting problems and is used to monitor the blood thinner heparin.
What high values can mean
A higher value (longer time) can mean slower clotting, from clotting-factor deficiencies, some medications or heparin.
What low values can mean
A lower value is less common and is usually interpreted in context.
How to improve it
aPTT reflects clotting function or medication; it is managed medically, not by lifestyle.
Food & lifestyle
No specific food targets aPTT; if you take blood thinners, keep your clinician informed of major diet changes.
Preparing for the test
A blood test; fasting is not required — follow your lab's instructions.
When to talk to a doctor
An abnormal aPTT is interpreted by a doctor with PT/INR and your bleeding or clotting history.
Related markers
Sources
- MedlinePlus (NIH)
- Testing.com (AACC)
Content reviewed on June 26, 2026
Medical disclaimer
This content is for educational purposes only. It is not medical advice and does not diagnose, treat, or prevent any condition. Reference ranges vary between laboratories — always use the range printed on your report and discuss your results with a healthcare professional.
See your own values in context
Bllod turns your lab report PDFs into clear, tracked results — every marker organized, explained, and charted over time.