Reference — Hematology
Coagulation Labs Reference
The coag panel answers two questions: is this patient anticoagulated to target, and can they clot when they need to? Ranges below are common adult conventions — your laboratory’s ranges govern.
Educational use only. Anticoagulant titration and holds follow provider orders and facility protocols — report critical values per policy with read-back. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
The Panel
| Lab | Typical Range / Target | What It Monitors | Nursing Notes |
|---|---|---|---|
| PT (prothrombin time) | ≈11–12.5 sec | Extrinsic pathway; basis of the INR | Usually interpreted through INR rather than alone |
| INR | 0.8–1.1 (no anticoagulant) · warfarin therapeutic commonly 2–3 (2.5–3.5 mechanical valves) | Warfarin | High INR + bleeding signs → hold per order and notify; vitamin K is the reversal agent |
| aPTT | ≈30–40 sec · heparin therapeutic commonly ~1.5–2.5× control (often ~46–70 sec) | Unfractionated heparin (intrinsic pathway) | Drawn on a schedule during heparin infusions; protamine sulfate is the reversal agent |
| Anti-Xa | Per indication and assay (facility-specific targets) | Heparin or LMWH where used; increasingly preferred for heparin titration | Follow the protocol’s titration table — targets differ by drug and indication |
| Platelets | 150,000–400,000/µL | Quantity, not function — bleeding risk rises as counts fall | <50k: bleeding precautions and procedure risk; a rapid drop on heparin raises the HIT question |
| Fibrinogen | ≈200–400 mg/dL | Clotting substrate — consumed in DIC and massive hemorrhage | Low fibrinogen with bleeding points to cryoprecipitate per order |
| D-dimer | Negative/low (assay-specific cutoff) | Clot breakdown product — sensitive, not specific | Useful to rule out VTE in low-risk patients; elevated by surgery, infection, pregnancy — interpret in context |
The Pairings to Memorize
• Warfarin → PT/INR → vitamin K reverses it
• Heparin → aPTT (or anti-Xa) → protamine sulfate reverses it
• LMWH (enoxaparin) — routine monitoring usually unnecessary; anti-Xa where needed (renal impairment, pregnancy, extremes of weight)
• DOACs — no routine coag monitoring; specific reversal agents exist (e.g., idarucizumab for dabigatran, andexanet alfa for Xa inhibitors)
When Values Run High
A supratherapeutic INR or aPTT is a bleeding assessment, not just a phone call: gums, puncture sites, urine, stool, neuro status (the bleed that kills is intracranial), and vitals. Hold or adjust per order, anticipate reversal discussion at the extremes, and institute bleeding precautions while the number is high.
A falling platelet count on heparin (commonly >50% drop, typically days 5–10) raises heparin-induced thrombocytopenia — the paradox is clotting, not bleeding, and the response is stopping all heparin exposure per provider, including flushes.
Related Resources
Standards & sources
Fact-checked Jun 21, 2026This page is written to align with AABB (transfusion standards) · American Society of Hematology (ASH). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →