What Are the Risks of Combining Warfarin and Alcohol?

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  • Last Modified Date: 06 October 2019
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The risk of combining warfarin and alcohol is principally that they increase the likelihood of excessive bleeding. This may lead to a secondary risk that is dependent on the first. Injuries obtained during alcohol-related accidents, such as falls or car accidents during drunken driving, could be more dangerous. The relationship between these two substances is complex, though, and minimal ingestion of alcohol is not likely to significantly impact health. Usually, greater problems arise when people consume more than two to three drinks a day, and especially if warfarin use isn’t accompanied by regular blood testing.

Warfarin helps prevent blood clot formation by inhibiting the action of vitamin K. Alcohol has a slightly different mechanism but it also can prevent blood clots from forming or help break them up when they occur. To a certain degree, the action produced by these substances is desirable. It can prevent strokes or other emboli. On the other hand, prevention of clotting can be a bad thing when injury with bleeding occurs.

As warfarin’s action on the blood is greater than alcohol’s, it ordinarily requires certain precautions. Patients on the drug will take blood tests like the International Normalized Ratio (INR) or Prothrombin Time (PT) quite often to make sure that they are taking the drug at a safe dosage. Warfarin is so reactive with other foods, drugs and infections that most people require frequent tests and experience regular changes to their dose.


Due to the regularity of blood testing, using warfarin and alcohol together in reasonable amounts simply requires slight dosage modifications, as the INR or PT will reflect a longer clotting time. If alcohol is used in excess, tests may be unstable, and it may be difficult to prescribe an appropriate warfarin amount that doesn’t place patients at risk for perilously low clotting times. Also, occasionally, patients don’t get the tests they require and may not realize that they are in danger.

What this means is that most doctors allow their patients to use warfarin and alcohol together. This recommendation frequently depends on the individual’s agreement to get regular blood tests. Consumption above two to three drinks daily isn’t advised because no amount of warfarin may be safely administered with this much alcohol.

The combination of warfarin and alcohol in excess can create an indirect effect. Intoxicated people are more prone to accidents in vehicles or to simple falls, slips, or trips. If warfarin and alcohol are used together, there may be a greater chance of excess bleeding from injuries, which might prove fatal. The combination of blood monitoring, never operating a vehicle after drinking, and keeping alcohol consumption to safe and moderate levels largely eliminates this secondary risk.


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Post 3

I'm on warfarin therapy and my doctor told me not to drink. She said that alcohol increases the effects of alcohol. So in a way, it's like taking more warfarin, except that alcohol comes with its own side effects. Alcohol is not very good for the body anyway. It depresses the central nervous system. It can affect motor control and vital functions. It can cause anxiety and depression, and it can harm the stomach.

Post 2

@SarahGen-- I'm not sure, I'm not an expert on this topic.

I suppose the warfarin and alcohol interaction would strain certain organs like the kidneys or the liver. But I'm sure it depends on the dose. The bigger risk with high doses of warfarin and large amounts alcohol would be internal bleeding, since both have an effect of thinning the blood. The combination could also cause upset stomach or other stomach complications.

It's best to avoid alcohol while on warfarin. I know that most people would like to have a drink now and then on special occasions. If the doctor is okay with this, then obviously it's fine. But regular drinking or drinking large amounts of alcohol can be very dangerous. I personally avoid alcohol altogether because I already experience side effects from warfarin and I don't want to experience more.

Post 1

Can the combination of alcohol and warfarin harm internal organs?

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