aPTT (Activated Partial Thromboplastin Time)
CoagulationNormal range
30–40 s · therapeutic on heparin: typically 1.5–2.5× control (per protocol)
Critical high: > 100 s (typical critical)
☎ When to call
aPTT above your protocol's critical threshold, any bleeding on a heparin drip, or aPTT that won't come up despite titration — call per protocol.
What you do
- Drives the heparin drip — draw on time, titrate exactly per protocol, document the change
- Supratherapeutic: assess for bleeding; per protocol may hold and rate-change
- Know protamine is the heparin antidote
Causes of HIGH aptt
Causes of LOW aptt
Source: Pagana, Mosby's Manual of Diagnostic and Laboratory Tests, 7th ed.Reference only — verify against your facility's policy.
