What INR ranges does this calculator support?

The calculator supports the three most common target ranges: 1.5–2.0 (low-intensity), 2.0–3.0 (standard), and 2.5–3.5 (high-intensity, e.g., mechanical heart valves). You can also enter a custom range.

How are the adjustment percentages determined?

Adjustments follow standard anticoagulation clinic protocols: no change when INR is on target; 5–10% change for minor deviations; 10–20% for moderate deviations; and larger adjustments (with a hold recommendation) when INR is critically high (above 4.0) or critically low.

Does this tool replace advice from my anticoagulation clinic?

No. This calculator is for educational reference only. Always follow guidance from your prescribing clinician or anticoagulation service. Individual factors like drug interactions, diet, and illness affect INR and are not captured here.

What if my INR is above 4.0?

An INR above 4.0 may indicate supratherapeutic anticoagulation with bleeding risk. The calculator will recommend holding one or more doses and rechecking INR, but you should contact your healthcare provider promptly.

Can I use this for pediatric patients?

No. Pediatric warfarin dosing uses weight-based protocols and differs significantly from adult protocols. This tool is designed for adult patients only.

Warfarin Dosing Calculator

Name: Warfarin Dosing Calculator
Availability: InStock
Author: Nham Vu

Adjust warfarin weekly dose based on current INR vs. target INR range using standard clinical dose-adjustment protocols.

Medical disclaimer: This tool is for educational reference only. Warfarin dosing must be supervised by a licensed clinician or anticoagulation service. Do not alter your dose without professional guidance.

INR & Dose Inputs

Current INR

Target INR Range

Current Weekly Dose (mg)

Total milligrams taken across the entire week (e.g. 5 mg/day × 7 = 35 mg/week)

Summary

Adjust warfarin weekly dose based on current INR vs. target INR range using standard clinical dose-adjustment protocols.

How it works

Enter your most recent INR (International Normalized Ratio) value.
Select or enter your target INR range (e.g., 2.0–3.0 for most indications).
Enter your current total weekly warfarin dose in milligrams.
Click "Calculate" to see the recommended dose adjustment percentage and new weekly dose.
Review the dose recommendation and medical disclaimer before making any changes.

Use cases

Verify a dose-adjustment recommendation from a clinical protocol chart.
Estimate the new weekly dose after an INR result comes back out of range.
Cross-check a pharmacist or anticoagulation clinic recommendation.
Understand whether a minor INR deviation warrants a dose change.

Frequently Asked Questions

Last updated: 2026-07-26 · Reviewed by Nham Vu