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Coumadin adjustment calculator

by Mark Morgan on January 15, 2011

Tagged as: anticoagulation, calculator, coumadin, warfarin

summary, references, & relevant links
Summary: This calculator guides a medical provider through adjustment of coumadin (warfarin) dosing.
Point-of-Care Guide and paper-based encounter form at Ebell (2005) Am Fam Physician 71: 1979-82.
University of Michigan Anticoagulation Management Service warfarin adjustment protocol.
Comprehensive article at Ansell (2001) Chest 119: 22S-38S.

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BEGIN: There are two calculators, one for goal INR of 2 to 3 and one for goal INR of 2.5 to 3.5. Click on the appropriate link below to select which calculator.

CHOOSE: Calculator for INR goal 2 to 3 or Calculator for INR goal 2.5 to 3.5

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INR goal 2 to 3

maintained at soapnote.org.
Current weekly dose (add up all days' doses)
Current INR
Number of consecutive weekly in-range INRs prior to this INR?
Bleeding?
- No significant bleeding
- Serious bleeding
- Life-threatening bleeding
INR < 1.5. Recommended increase is 10 to 20%
12.5 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may consider manually adding a dose if necessary (see below).
INR 1.5 to 1.7. Recommended increase is 5 to 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may consider adding a dose if necessary (see below).
INR 1.8 to 1.9. Recommended increase is 5 to 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. At this zone, it is often appropriate to leave the dose unchanged and simply recheck in 7 to 14 days.
INR 2 to 3. No change is recommended
INR 3.1 to 3.2. Recommended decrease is 5 to 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. At this zone, it is often appropriate to leave the dose unchanged and simply recheck in 7 to 14 days.
INR 3.3 to 3.9. Recommended decrease is 5 to 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may consider manually subtracting a dose if necessary (see below).
INR 4.0 to 4.9. Recommendation is to hold for 0 - 1 day, then decrease 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may also consider manually subtracting a dose if necessary (see below).
INR 5.0 to 8.9. Recommendation is to hold for 1 - 2 days, decrease 10 to 20%, and consider vitamin K
12.5 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may consider manually subtracting a dose if necessary (see below).
INR 9.0 or more. Recommendation is to hold warfarin therapy; give vitamin K1 5.0 to 10 mg orally; monitor frequently. Resume at lower dose when INR is therapeutic
Manual override: Add or subtract a 2.5 mg dose to new weekly total?
- No
- Add 2.5 mg dose
- Subtract 2.5 mg dose
At lower weekly doses and/or at zones close to the goal INR, occasionally the new recommended weekly dosage will be unchanged. Often this indicates that a dosage change is not warranted and retesting should be performed at the recommended interval. You can, however, manually change the recommended dose by adding or subtracting a dose. You may do so by making a selection above.

Result - Paste this into your EHR:

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INR goal 2.5 to 3.5

maintained at soapnote.org.
Current weekly dose (add up all days' doses)
Current INR
Number of consecutive weekly in-range INRs prior to this INR?
Bleeding?
- No significant bleeding
- Serious bleeding
- Life-threatening bleeding
INR < 1.5. Recommended increase is 10 to 20%
12.5 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may consider manually adding a dose if necessary (see below).
INR 1.5 to 2.2. Recommended increase is 5 to 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may consider adding a dose if necessary (see below).
INR 2.3 to 2.4. Recommended increase is 5 to 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. At this zone, it is often appropriate to leave the dose unchanged and simply recheck in 7 to 14 days.
INR 2.5 to 3.5. No change is recommended
INR 3.6 to 3.7. Recommended decrease is 5 to 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. At this zone, it is often appropriate to leave the dose unchanged and simply recheck in 7 to 14 days.
INR 3.8 to 4.4. Recommended decrease is 5 to 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may consider manually subtracting a dose if necessary (see below).
INR 4.5 to 5.9. Recommendation is to hold for 1 - 2 days, then decrease 10%
25 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may also consider manually subtracting a dose if necessary (see below).
INR 6.0 to 8.9. Recommendation is to hold for 1 - 2 days, decrease 10 to 20%, and consider vitamin K
12.5 mg is the minimum weekly dose threshold to make a significant dosage change for this INR zone. You may consider manually subtracting a dose if necessary (see below).
INR 9.0 or more. Recommendation is to hold warfarin therapy; give vitamin K1 5.0 to 10 mg orally; monitor frequently. Resume at lower dose when INR is therapeutic
Manual override: Add or subtract a 2.5 mg dose to new weekly total?
- No
- Add 2.5 mg dose
- Subtract 2.5 mg dose
At lower weekly doses and/or at zones close to the goal INR, occasionally the new recommended weekly dosage will be unchanged. Often this indicates that a dosage change is not warranted and retesting should be performed at the recommended interval. You can, however, manually change the recommended dose by adding or subtracting a dose. You may do so by making a selection above.

Result - Paste this into your EHR:

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{ 5 comments… read them below or add one }

Mark Morgan April 16, 2011 at 8:22 am

I updated the calculators. They now have a recommendation for follow-up INR testing.

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rmerrill November 19, 2011 at 1:26 pm

Thanks for the nice calculator. Is it possible to modify it to actually quote the dose adjustment…such as “reduce/ increase weekly dose to…” I am looking for tools to use on my iPhone/ iPad.

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Mark Morgan November 29, 2011 at 6:13 am: I added the words “NEW DOSE” just after “Recommended adjustment” so that users can compare the “Current weekly dose” to the “NEW DOSE”. If you’ve only selected a small percentage increase or decrease, it’s possible they would be the same. I didn’t want to make any dramatic changes because a lot of people rely on this calculator. Thank you for your suggestion. I hope this helps!

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Marv December 18, 2011 at 1:05 am

Is there an iPhone app for the warfarin calculators?

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Mark Morgan December 18, 2011 at 2:01 pm

Hi. No iPhone app yet, but in the next few days I’ll be releasing changes which should make it easier to use and view on all mobile devices.

Thanks for using soapnote!

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Coumadin adjustment calculator

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