# Warfarin Dose Adjustment Calculator (INR Nomogram)

Adjust warfarin maintenance dose from the current INR using the standard nomogram for a target INR of 2.0–3.0. No-bleed ladder: INR<1.5 → +10–20% weekly dose; 1.5–1.9 → +5–15%; 2.0–3.0 → no change; 3.1–3.5 → −5–15%; 3.6–4.0 → −10–20%; 4.1–4.4 → hold 0–1 dose, ~−20%; 4.5–10 → hold + oral vitamin K₁ 1–2.5 mg; >10 → hold + oral vitamin K₁ 2.5–5 mg. Serious/life-threatening bleed at any INR → hold warfarin, vitamin K₁ 5–10 mg IV (slow, 20–30 min) + 4-factor PCC (FFP if unavailable). Optional current weekly dose computes the concrete new weekly and daily dose. Derived from the 9th-edition ACCP Guidelines (Holbrook et al., Chest 2012) and the UW Anticoagulation Clinic nomogram. Valid for adult maintenance therapy at steady state; not for initial induction, DOAC/heparin overlap, or perioperative bridging. Not medical advice.

> Canonical page: https://elysiatools.com/en/tools/warfarin-dose-adjustment

- **Category:** Health

- **Keywords:** warfarin, coumadin, INR, nomogram, dose adjustment, vitamin K, phytonadione, PCC, anticoagulation, reversal, bleeding, prothrombin time, ACCP

## Overview

The Warfarin Dose Adjustment Calculator uses the current INR and optional weekly warfarin dose to apply a standard nomogram for an INR target of 2.0–3.0. It returns an adjustment range, possible vitamin K recommendations, and follow-up timing for adult maintenance therapy at steady state; it is not medical advice.

## Inputs

- **Current INR** (number): Current INR (prothrombin time ratio). Must be positive.
- **Current weekly dose (mg, optional)** (number): Optional current total weekly warfarin dose in mg. Used to compute the new concrete weekly/daily dose.
- **Serious / life-threatening bleeding?** (checkbox): If checked, the tool switches to the full-reversal pathway (hold + IV vitamin K₁ + PCC) regardless of INR.
- **Decimal Places** (number)

## When to use

- Estimate a maintenance-dose adjustment after entering a current INR.
- Convert a recommended percentage change into an approximate weekly and daily dose by entering the current weekly dose.
- Review the nomogram pathway for a high INR or serious bleeding, including hold, vitamin K, and PCC recommendations.

## How it works

- Enter the current positive INR.
- Optionally enter the current total weekly warfarin dose to calculate a concrete new weekly and daily dose range.
- Select the serious or life-threatening bleeding option when applicable; this switches to the full-reversal pathway regardless of INR.
- The calculator returns the INR category, recommended action, dose-change range, vitamin K guidance, and suggested recheck interval as JSON.

## Use cases

- Anticoagulation clinic review of an out-of-range maintenance INR.
- Estimating weekly and daily dose ranges from a known current weekly warfarin dose.
- Checking the appropriate nomogram pathway for elevated INR or serious bleeding before clinical action.

## Frequently asked questions

### What INR target does this calculator use?

It uses the standard maintenance target range of 2.0–3.0.

### Can I calculate a new weekly warfarin dose?

Yes. Enter the optional current weekly dose to calculate the recommended weekly and daily dose range.

### What happens if serious bleeding is selected?

The calculator recommends holding warfarin, IV vitamin K1 5–10 mg, and 4-factor PCC, with FFP if PCC is unavailable, regardless of INR.

### Does the calculator cover high INR without bleeding?

Yes. It provides hold and oral vitamin K1 guidance for INR ranges from 4.5 to above 10.

### Who is this calculator intended for?

It is intended for adult maintenance therapy at steady state, not initial induction, DOAC or heparin overlap, or perioperative bridging.

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