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Warfarin Dosing

Warfarin Dosing: calculated with the published clinical method, with result interpretation. A reference tool that does not replace a doctor's advice.

ℹ Reference calculation based on the published method. It does not replace a clinical examination or a doctor's decision.

Warfarin Dosing

Ageyears
Heightcm
Body weightkg
Race (0 White, 1 Asian, 2 Black, 3 mixed or unspecified)
Carbamazepine, phenytoin or rifampicin (1 = yes)
Amiodarone (1 = yes)
VKORC1 −1639 (0 unknown, 1 G/G, 2 G/A, 3 A/A)
CYP2C9 (0 unknown, 1 *1/*1, 2 *1/*2, 3 *1/*3, 4 *2/*2, 5 *2/*3, 6 *3/*3)
Warfarin maintenance dose
4.25mg/day
Estimate of stable dose; titrate by INRVerify the dose against the product labelWarfarin Dosing: calculated with the published clinical method, with result interpretation. A reference tool that does not replace a doctor's advice.
Weekly dose
29.7mg/week
Algorithm
IWPC clinical

More about: Warfarin Dosing

What it calculates

The “Warfarin Dosing” calculator computes Warfarin maintenance dose in mg/day from 8 parameters: age (years), height (cm), body weight (kg), race (0 white, 1 asian, 2 black, 3 mixed or unspecified), carbamazepine, phenytoin or rifampicin (1 = yes), amiodarone (1 = yes), vkorc1 −1639 (0 unknown, 1 g/g, 2 g/a, 3 a/a), cyp2c9 (0 unknown, 1 *1/*1, 2 *1/*2, 3 *1/*3, 4 *2/*2, 5 *2/*3, 6 *3/*3).

Used by professionals and patients to assess health metrics, dosages, and risks.

Example calculation

With parameters Age = 65 years, Height = 170 cm, Body weight = 70 kg, Race (0 White, 1 Asian, 2 Black, 3 mixed or unspecified) = 0, Carbamazepine, phenytoin or rifampicin (1 = yes) = 0, Amiodarone (1 = yes) = 0, VKORC1 −1639 (0 unknown, 1 G/G, 2 G/A, 3 A/A) = 0, CYP2C9 (0 unknown, 1 *1/*1, 2 *1/*2, 3 *1/*3, 4 *2/*2, 5 *2/*3, 6 *3/*3) = 0 the result is 4.25 mg/day (Estimate of stable dose; titrate by INR).

How to use

  1. Enter age, height, body weight, race (0 white, 1 asian, 2 black, 3 mixed or unspecified), carbamazepine, phenytoin or rifampicin (1 = yes), amiodarone (1 = yes), vkorc1 −1639 (0 unknown, 1 g/g, 2 g/a, 3 a/a) and cyp2c9 (0 unknown, 1 *1/*1, 2 *1/*2, 3 *1/*3, 4 *2/*2, 5 *2/*3, 6 *3/*3) — each field above is adjustable with a slider.
  2. Warfarin maintenance dose (mg/day) is calculated automatically as you type.
  3. Check the worked example below to see the formula applied to real numbers.
  4. Copy the result or bookmark this calculator.

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FAQ

How is BMI calculated?
BMI = weight (kg) / height (m)². Example: 70 kg / (1.75 m)² = 22.9. The WHO normal range is 18.5–24.9; below that is underweight, 25–29.9 is overweight, and 30+ is obese.
Is BMI accurate for everyone?
No. BMI does not distinguish muscle from fat, so athletes may show a high BMI with low body fat. It is also less reliable for teenagers, pregnant people, older adults, and very tall or short individuals.
What are the BMI categories?
Underweight: below 18.5. Normal: 18.5–24.9. Overweight: 25–29.9. Obese class I: 30–34.9; class II: 35–39.9; class III: 40+.
What is a better measure than BMI?
Body fat percentage, waist-to-height ratio (aim for under 0.5), and waist circumference give a clearer picture of health than BMI alone.

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