Warfarin Dose Adjustment for INR 1.9
Increase your weekly warfarin dose by 15-20%, which translates to approximately 10 mg daily (or alternating 10 mg and 9 mg) for the next 5-7 days, then recheck INR in 3-5 days. 1
Rationale for Dose Increase
Your current INR of 1.9 is below the therapeutic target of 2.0-3.0, placing you at increased risk for thromboembolic events. 1 The American College of Chest Physicians specifically recommends increasing the weekly warfarin dose by 10-20% when the INR remains substantially below target. 1
Specific Dosing Calculation
- Current weekly dose: 8.5 mg × 7 days = 59.5 mg/week 1
- Target weekly dose (15-20% increase): 68-71 mg/week 1
- Practical dosing strategy: Take 10 mg daily for 5-7 days, which provides approximately 70 mg/week 1
- Alternative approach: Alternate between 10 mg and 9 mg daily to fine-tune the dose 1
Monitoring Strategy
Recheck your INR in 3-5 days, not 1-2 weeks. 1 When the INR is significantly subtherapeutic like yours, waiting the standard 1-2 weeks is inappropriate and delays achieving therapeutic anticoagulation. 1
Critical Pitfalls to Avoid
- Do not give vitamin K when the INR is subtherapeutic—this is only for elevated INR situations 1
- Do not hold warfarin doses when below therapeutic range 1
- Bridging with heparin is not routinely needed for a single low INR reading 1
- Avoid making only small adjustments (5-10%) when the INR is substantially below target, as this prolongs the time to reach therapeutic levels 1
Factors to Investigate
Before finalizing your dose adjustment, review these potential causes of subtherapeutic INR:
- Drug interactions: Check for new medications that may decrease warfarin effect 1
- Dietary vitamin K intake: Increased consumption of vitamin K-rich foods (leafy greens) can lower INR 1
- Medication adherence: Confirm you're taking warfarin consistently 1
- Consider pharmacogenetic testing if INR remains refractory after appropriate dose escalation 1
Why This Matters
The risk of thromboembolism is significantly greater when INR falls below 2.0. 2 Studies demonstrate that maximum efficacy for stroke prevention requires an INR >2.0, though some benefit remains at 1.5-1.9. 2 Your current INR of 1.9 provides suboptimal protection against clot formation.