Warfarin Dose Adjustment for INR 1.7 (Target 2.0)
Increase your weekly warfarin dose by 10-20% and recheck the INR in 3-7 days. 1, 2
Specific Dose Calculation
- Current regimen: 4 mg daily = 28 mg per week
- Recommended increase: 10-20% of weekly dose = 2.8-5.6 mg additional per week
- New weekly total: 30.8-33.6 mg per week 1
Practical dosing options:
- Conservative approach (10% increase): 31 mg/week
- Example: 4.5 mg daily (using combination of 5 mg and 4 mg tablets on alternating days) 2
- Moderate approach (15% increase): 32 mg/week
- Example: 4.5 mg on 4 days, 4 mg on 3 days per week 1
Follow-Up Monitoring
- Recheck INR in 3-7 days after dose adjustment to assess response 1, 2
- Once therapeutic INR (2.0-3.0) is achieved and sustained for 2 consecutive days, reduce monitoring frequency to 2-3 times weekly for 1-2 weeks 3, 2
- After stability is confirmed, monitor weekly for 1 month, then every 2-4 weeks 2
Investigation of Underlying Causes
Before simply increasing the dose, identify reversible factors that may have caused the INR drop: 2
- Dietary changes: Increased vitamin K intake from leafy greens, liver, or nutritional supplements 3, 2
- Medication compliance: Missed doses or irregular timing 2
- Drug interactions: Newly started medications (antibiotics, NSAIDs, herbal supplements) that may reduce warfarin effect 1, 2
- Intercurrent illness: Conditions affecting absorption or metabolism 2
Bridging Anticoagulation Consideration
Do not routinely bridge with heparin for a single subtherapeutic INR. 3, 1
The American College of Chest Physicians found no significant difference in thromboembolic events between bridged and non-bridged patients with single subtherapeutic INR values (Grade 2C). 3
Exceptions requiring bridging consideration:
- Mechanical mitral valve 1
- Recent thromboembolism within 3 months 1
- History of thromboembolism while anticoagulated 1
For these very high-risk patients, consider enoxaparin 1 mg/kg subcutaneously twice daily or 1.5 mg/kg once daily until INR reaches therapeutic range. 2
Common Pitfalls to Avoid
- Do not administer vitamin K for subtherapeutic INR—vitamin K is only indicated for elevated INR values with or without bleeding 1
- Avoid dramatic daily dose changes—increase the total weekly dose by 10-20% rather than making large single-day adjustments, as this provides more stable anticoagulation 2
- Do not over-monitor—excessive INR testing without clinical indication raises costs and patient burden without improving outcomes 2