Warfarin is the most widely prescribed anticoagulant in the UK. It works by decreasing the clotting ability of your blood which lowers the likelihood of blood clots. It is known be highly effective in reducing the risk of stroke for people with an irregular abnormal heart rhythm called atrial fibrillation (AF). It’s estimated that 60% of people taking warfarin have AF.
It is also commonly prescribed for people who have had a mechanical heart valve replacement, to stop clots forming on the valve. Warfarin can also prevent the mechanical valve from failing. If the valve were to become covered in blood clots it wouldn’t work properly.
You will continue to keep taking warfarin for as long as you are at high risk of developing a blood clot. For people with AF or a mechanical valve this is likely to be lifelong.
If you are prescribed warfarin you will need regular blood tests called international normalised ratio (INR). These measure how long it takes your blood to clot. The higher your INR the longer it takes for your blood to clot. However, if this becomes too high there is an increased risk of bleeding whereas a low INR will not provide enough protection against clotting. The target INR is 2.5, after tests your dose is adjusted to get as close to this target as possible. If you’ve just started taking warfarin you may need these tests done weekly. As your INR becomes stable you may only need an INR test every 8 weeks.
Side Effects:
Despite the benefits of warfarin, the risk of bleeding is increased. Serious bleed risk is roughly 1-2 % each year. Keeping your INR on target reduces this risk. Everyday bleeds aren’t a cause for concern you may just bleed for a longer period of time. It is recommended to avoid contact sports to reduce the risk of getting an injury which can cause bleeding. For any head injuries, it is advised to seek medical help immediately to rule out any internal bleeding which is not always obvious.