Warfarin scheme – reference ranges

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These reference ranges are to help with interpreting results for patients on a Warfarin scheme.

Day APTT (9-10am) target Heparin dose IF INR Warfarin dose given at 5pm
1 Start 2-3 ratio As per APTT < 1.4 10 mg
2

As per APTT

< 1.8

1.8

> 1.8

10 mg

1 mg

0.5 mg

3

2-3 ratio

As per APTT

< 2.0

2.0-2.3

2.4-2.7

2.8-3.1

3.2-3.4

3.5-4.0

> 4.0

10 mg

5 mg

4 mg

3 mg

2 mg

1 mg

NIL

4

Stop Heparin

<1.4

1.4

1.5

1.6-1.7

1.8

1.9

2.0-2.1

2.2-2.3

2.4-2.6

2.7-3.0

3.1-3.5

3.6-4.0

4.1-4.5

>4.5

Predicted Maintenance

>8 mg

8 mg

7.5.mg

7 mg

6.5 mg

6 mg

5.5 mg

5 mg

4.5 mg

4 mg

3.5 mg

3 mg

Nil then 2mg

 

Nil for two days and then 1 mg

(Last reviewed October 2018)