Warfarin Dose Adjustment for INR 1.7 with Target 2.5–3.5
Increase your weekly warfarin dose by 10–15% from the current 26 mg/week, bringing the new weekly total to approximately 29–30 mg per week. 1
Dose Calculation and Rationale
The European Heart Association recommends a 10–15% increase in total weekly dose for patients with an INR of 1.9 targeting 2.5–3.5; your INR of 1.7 is even further below target and warrants at least a 10% increase. 1
Current weekly dose: 26 mg (6 mg Friday + 4 mg × 4 days + 2 mg × 2 days = 26 mg/week)
10% increase: 26 mg × 1.10 = 28.6 mg/week (round to 29 mg)
15% increase: 26 mg × 1.15 = 29.9 mg/week (round to 30 mg)
Given your INR is 1.7 (substantially subtherapeutic for a 2.5–3.5 target), I recommend the higher end: 30 mg/week. 1
Practical Weekly Schedule Options
Option 1 (simplest):
- 4 mg daily Monday through Saturday (24 mg)
- 6 mg on Sunday (6 mg)
- Total: 30 mg/week
Option 2 (maintains your Friday pattern):
- 6 mg on Friday
- 4 mg on Monday, Wednesday, Saturday, Sunday (16 mg)
- 3 mg on Tuesday and Thursday (6 mg)
- Total: 30 mg/week
Option 3 (alternate-day dosing with single tablet size):
- 5 mg on Monday, Wednesday, Friday, Sunday (20 mg)
- 2.5 mg on Tuesday, Thursday, Saturday (7.5 mg)
- Total: 27.5 mg/week (closer to 10% increase)
Immediate Dosing Consideration
The European Society of Cardiology states that today's dose should be 2.5–3 mg to begin correcting the subtherapeutic level, then resume your adjusted maintenance schedule starting tomorrow. 1
This single higher dose helps bridge the gap while the increased maintenance dose takes effect over the next several days. 1
Why This Target Range (2.5–3.5) Matters
An INR target of 2.5–3.5 is recommended for high-risk thrombosis patients, such as those with mechanical mitral valves or history of thromboembolism despite standard anticoagulation. 1
Each day below therapeutic range increases thrombotic risk by approximately 0.03–0.05% in high-risk patients with mechanical valves. 1
Your current INR of 1.7 leaves you significantly underprotected against thrombosis. 1
Critical Error to Correct
The European Society of Cardiology emphasizes that dose reduction over the past 3 days was inappropriate and caused the INR to drift downward. 1
Given your target range of 2.5–3.5, you require dose escalation, not reduction. 1
Avoid making the same mistake of reducing doses when INR appears "high" relative to the standard 2.0–3.0 range—your target is different. 1
Monitoring Strategy
Recheck INR in 3–5 days after implementing the dose adjustment to assess response. 1
Once INR stabilizes within the therapeutic range (2.5–3.5), extend monitoring to weekly, then every 2–4 weeks. 1
The American College of Cardiology recommends checking INR 2–3 times weekly for 1–2 weeks after achieving therapeutic range to confirm stability. 2
Common Pitfalls to Avoid
Do not make excessive dose changes for single INR deviations, but your patient has a consistent downward trend requiring intervention. 1
Do not overreact to the recent dose reduction—simply return to a higher stable dose plus the 10–15% increase, rather than making dramatic changes that cause INR instability. 1
Ensure consistent vitamin K intake, as fluctuations affect warfarin response and can explain unexpected INR changes. 1
Review for drug interactions, particularly NSAIDs, antibiotics, or new medications that may have contributed to INR changes. 1
Factors to Investigate Before Next Dose
New medications or antibiotics are the most common cause of unexpected INR changes. 2
Dietary changes affecting vitamin K intake (increased green vegetables or supplements can lower INR). 2
Intercurrent illness, poor oral intake, or gastrointestinal symptoms can alter warfarin absorption. 2
Medication adherence—confirm the patient is taking warfarin as prescribed. 2