Starting Warfarin
| Day | International Normalized Ratio (INR), best checked 09.00–10.00h | Dose of wafarin (mg) to be given that evening (17.00–18.00h) |
|---|---|---|
| 1 | 1.4 or above | Establish cause of coagulation disorder |
| Do not start warfarin before discussion with a haematologist | ||
| <1.4 | 10 | |
| 2 | <1.8 | 10 |
| 1.8 | 10 | |
| <1.8 | 5 | |
| 3 | <2.0 | 10 |
| 2.0–2.1 | 5 | |
| 2.2–2.3 | 4.5 | |
| 2.4–2.5 | 4 | |
| 2.6–2.7 | 3.5 | |
| 2.8–2.9 | 3 | |
| 3.0–3.1 | 2.5 | |
| 3.2–3.3 | 2 | |
| 3.4 | 1.5 | |
| 3.5 | 1 | |
| 3.6–4.0 | 0.5 | |
| >4.0 | Give none | |
| 4 | <1.4 | Ask advice from a haematologist |
| 1.4 | 8 | |
| 1.5 | 7.5 | |
| 1.6–1.7 | 7 | |
| 1.8 | 6.5 | |
| 1.9 | 6 | |
| 2.0–2.1 | 5.5 | |
| 2.2–2.3 | 5 | |
| 2.4–2.6 | 4.5 | |
| 2.7–3.0 | 4 | |
| 3.1–3.5 | 3.5 | |
| 3.6–4.0 | 3 | |
| 4.1–4.5 | Miss 1 day, then give 2 mg | |
| >4.5 | Miss 2 days, then give 1 mg |
Source: Fennerty A, Campbell IA, Routledge PA, et al. (1988) Anticoagulants in venous thromboembolism. British Medical Journal 297, 1285–8. Reproduced with permission of BMJ Publishing Group Ltd.