Does Alcohol Thin Your Blood?

Effects of Moderate Drinking on Your Health

Mature woman at desk reading book by glass of red wine
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Moderate drinking is a two-edged sword. It may have some beneficial effects, but at the same time, those very same effects could be negative in other areas of your health.

Moderate drinking is also a balancing act, of sorts. If you drink exactly the right amount to be "moderate" it may be better in some health effects than not drinking at all, but if you drink just a tad over the guidelines for moderate, it is much more dangerous than not drinking at all.

It's called the J-curve.

Take blood coagulation, for example. If you drink a moderate amount of alcohol—defined in one large study as three to six drinks per week—it may have the benefit of acting as a blood thinner and be protective against clotting in clogged arteries, like aspirin does. At the same time, thinning the blood can hasten bleeding from injured arteries, increasing the risk of bleeding strokes.

Precautions Against Drinking Alcohol While Taking Blood Thinners

You should abstain from alcohol while taking anticoagulant blood thinners such as Coumadin (warfarin) as the blood-thinning effects of alcohol can interact with those of the prescribed drugs. It will be more difficult for your healthcare providers to determine the correct dosage for the prescribed blood thinner if you also drink alcohol. As you will be placed on blood thinners to prevent a significant health threat, such as a deep venous thrombosis, it's best not to take the risk and have an alcoholic beverage.

Also, consider the other prescriptions that you take. Sometimes they interact with blood thinners and alcohol. Follow the precautions and refrain from drinking if that is recommended.

Don't Substitute Alcohol for Prescription Blood Thinners

Likewise, if you need anticoagulation to reduce a health risk, it is unwise to think that drinking alcohol is a substitute for prescribed blood thinners.

When your doctor prescribes an anticoagulant such as Coumadin, you will also have your blood tested regularly to ensure you are getting just the right amount of blood thinning. Too little and you aren't protected. Too much and you risk bleeding.

Contrasting Effects of Alcohol on Coagulation

Some studies have shown that moderate drinkers tend to have lower rates of heart disease, but higher rates of bleeding-type strokes than abstainers. However, some researchers believe that the ability of moderate drinking to make blood platelets less "sticky" may mediate the negative effects of moderate drinking.

"The contrasting effects of alcohol are similar to the effects of blood thinners like aspirin, which clearly prevent heart attacks but at the expense of some additional bleeding strokes," said Kenneth J. Mukamal, corresponding author for a study on effects of moderate drinking on blood coagulation. "Acting as a blood thinner makes sense, because heart attacks are caused by blood clots that form in clogged arteries, and blood thinners can hasten bleeding from injured arteries. Based on these findings, we speculated that moderate drinking would also act as a blood thinner."

Mukamal said previous research had shown that moderate drinkers tend to have "less sticky" platelets than abstainers, meaning that fewer blood elements cluster to form blood clots.

He studied 5,124 men and women enrolled in the Framingham Offspring Study of risk factors for cardiovascular disease.

"We found that among both men and women, an intake of three to six drinks per week or more was linked to lower levels of stickiness measured by aggregability," said Mukamal. "Among the men, we also found that alcohol intake was linked to lower levels of platelet activation. Together, these findings identify moderate drinking as a potential blood thinner."

No Reason to Start Drinking

"Our findings add to a large body of evidence showing that moderate drinking has effects on blood coagulation, which may have both good and bad effects, but now identify a new avenue by which this effect may occur," said Mukamal.

"By themselves, these findings have more importance for understanding risk factors for vascular disease than any clinical relevance, and should not be used by people as any reason to begin drinking."

Meanwhile, there is increasing skepticism among researchers that moderate drinking has protective health effects for heart disease, according to the CDC. The bottom line is, although moderate drinking may have some health benefits, there is risk involved, too. If you don't drink, the risks of developing other problems associated with alcohol may be too great to begin drinking for its limited benefits.


Fact Sheets - Moderate Drinking. CDC.

Mukamal, KJ, et al. " Alcohol Consumption and Platelet Activation and Aggregation Among Women and Men: The Framingham Offspring Study." Alcoholism: Clinical & Experimental Research October 2005

Taking Warfarin (Coumadin) NIH MedlinePlus.

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