Is my aPTT result normal?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

Does the prolongation indicate bleeding risk?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

Could lupus anticoagulant be a factor?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

What factors may be affecting my result?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

How often should I be retested?

For evidence-based information about aPTT (Activated Partial Thromboplastin Time) Test, visit this page.

Home → Tests → aPTT

aPTT (Activated Partial Thromboplastin Time) Test

✅ Up to date🔬 Evidence: ModerateHematology

Diğer adları: APTT test, Partial thromboplastin time, PTT

⚠️

Discuss your test results with your doctor. This page is for informational purposes only and does not provide a diagnosis.

⚡ Key Facts

• Measures clotting time via the intrinsic and common pathways • Normal: approximately 25–40 seconds • Used for heparin monitoring and bleeding disorder investigation • Lupus anticoagulant may cause prolongation without bleeding risk

🧪 What Does This Test Measure?

The aPTT test measures clotting time through the intrinsic and common pathways, used for heparin monitoring and bleeding disorder investigation.

📋 Why Is It Ordered?

Ordered for bleeding disorder investigation, unfractionated heparin monitoring, and preoperative clotting assessment.

🔧 Preparation

Fasting is generally not required. Blood is collected in a citrated tube. Sample handling and timing are important for accuracy.

📊 Reference Ranges

Normal: approximately 25–40 seconds (varies by laboratory) UFH therapeutic range: typically 1.5–2.5× the control value ⚠️ Ranges vary by laboratory and reagent.

⬆️ High Values

Prolonged aPTT may be associated with heparin therapy, factor deficiencies, lupus anticoagulant, or DIC.

⬇️ Low Values

Shortened aPTT is rarely evaluated clinically. It may be seen with acute phase response or elevated factor VIII.

⚙️ What Can Affect Results?

Medications, sample collection technique, reagent type, elevated CRP or hematocrit, and delayed processing may affect aPTT results.

🔬 Evidence Summary

Moderate evidence: 4 guidelines and 3 reviews.

✅ Key Takeaways

💡

What you learned: aPTT evaluates the intrinsic clotting pathway. It is essential for heparin monitoring and bleeding disorder investigation.

⛔

An aPTT result alone cannot diagnose a bleeding or clotting disorder. Clinical context and additional tests are needed.

🔬 Sources Used on This Page

7 sources · Most recent publication: 2024

📋

Guideline

Expert society and guideline recommendations

sources

📖

Review

Comprehensive topic evaluation

sources

Overall assessment: Evidence level for this topic is moderate. This page is supported by 4 guidelines, 3 reviews.

📝 Questions to Ask Your Doctor

Be prepared for your appointment. Add questions to your list.

Last reviewed: 4/2/2026

Next review: 7/2/2026

⚖️ Comparisons

PT/INR vs aPTT→

🔗 Related Topics

🧪 PT/INR (protrombin zamanı)🧪 D-dimer🧪 Fibrinojen🧪 Hemogram (trombosit sayısı)

⚖️ This page does not replace medical advice. Make treatment decisions with your doctor.
Content is based on scientific studies indexed in PubMed and current clinical guidelines.