Aspirin vs. warfarin

July, 2015

The mythbuster edition

We thought we would bust a few myths around the aspirin vs. warfarin debate. In the past aspirin has been perceived as effective for stroke prevention. However, this is not the case. In fact, any patients who are at risk of a stroke due to atrial fibrillation should be considered for an oral anticoagulant, like warfarin. These days, many people are prescribed warfarin due to its effectiveness, so why are some people wary of it?

To help unravel some of the misconceptions surrounding warfarin we talked to Yorkshire-based GP, Matthew Fay:

Q: Should a patient be more nervous about warfarin than aspirin?

A: “I find that when people think about warfarin, often the first thing they have concerns about is the bleeding risk What people might not know is that aspirin also has a bleeding risk, but with aspirin the bleeding risk outweighs the benefits making it ineffective for stroke prevention.

Whilst there is a risk of bleeding with warfarin, self-testing means you’ll always be able to know your INR to help keep you informed and manage any bleeding risk.”

Q: Does the fact that warfarin is made from the same elements as rat poison mean that it is dangerous to take?

A: “Learning that warfarin is created with the same basic elements as rat poison is concerning to patients. This is why I always make this clear very early on, so there are no surprises. However, there really is no need to be worried. It’s a drug that’s been tried and tested for over 60 years and is known to significantly reduce the risk of strokes (unlike aspirin). The dosage used in rat poison is also deliberately high.”

Q: What has changed in the last few years in the debate between warfarin and aspirin?

A: “In terms of evidence, warfarin has been shown to be superior to aspirin for years. In recent times our understanding of anticoagulants has become far greater. With options like self-testing, we now have more confidence when issuing prescriptions for drugs like warfarin. Even NICE (National Institute for Health and Care Excellence) who provide national guidance on medicine usage in the UK have now removed aspirin usage from their recommendations (and in the same year recommended self-testing).

What’s more, the increase of options in anticoagulation has led to a better conversation with patients about their choices. Self-testing is also helping to take some of the strain off of the NHS and helping people to get on with their lives.”

Q: How do patients feel switching from aspirin to warfarin?

A: “I don’t ever find it to be an issue switching a patient from aspirin to warfarin. Using current medical guidelines, I discuss the treatment options with patients. If they choose warfarin, they generally end up happy with their choice. Some raise the point ‘I’ve had this condition for years and not had a stroke yet’, but I simply reiterate that this is just down to luck. An effective anticoagulant should always be used for those at risk.”

Q: What advice would you give to patients who have just switched from aspirin to warfarin?

A: “In terms of advice I’d say just live your life. We’ll build the warfarin dose around you, not the other way round. Plus don’t worry about milligrams of the medication; it’s your INR reading that is important. As a principle the more Vitamin K you eat, the more warfarin you will need to get an appropriate INR.”

Rest assured

We hope Dr Fay has helped to dispel any of the misconceptions you may have had about warfarin and aspirin. We’d like to thank him for his time. Plus if you or anyone you know is still using aspirin as a blood-thinner, remember to tell them to challenge their GP or HCP to stop using aspirin and use an effective anticoagulant.

Please note the opinions expressed here are those of Dr Matthew Fay. We would always recommend speaking to your own healthcare professional about your treatment options.

If you have any queries or concerns regarding the issues raised in this article, please do contact the CoaguChek team on the freephone care line number 0808 100 7666 or email us at

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