Blood Thinners And Drawing Blood

Experts say a daily dose of blood thinners and aspirin can increase the risk of bleeding. Pixels Effect/Getty Images

Researchers say people who use blood thinners probably shouldn't also take a daily aspirin.
They say the double dose of medication can increase the risk of bleeding and hospitalization.
Experts say a daily, low-dose aspirin can be beneficial to some people, although three times a week might be better than once a day.

More isn't always better, especially in medicine.

If you take blood thinners, adding aspirin to your daily regimen can be risky.

A new study published in JAMA Internal Medicine finds that treatment with certain blood thinners plus daily aspirin is associated with increased bleeding and hospitalizations.

The research involved adults taking direct oral anticoagulants (DOACs), including apixaban, dabigatran, edoxaban, and rivaroxaban. Some participants were transitioning to a DOAC from warfarin, another type of anticoagulant.

All participants were undergoing treatment for atrial fibrillation or venous thromboembolic disease.

Of the 3,280 study participants, 1,107 took daily low-dose aspirin with their DOAC even though there was no clear indication for doing so. Another 2,173 participants took their DOAC alone.

After a minimum of 3 months follow-up, the researchers found an association between DOACs plus low-dose aspirin and increased bleeding events as well as hospital admissions related to bleeding.

Blood thinners are typically prescribed to help prevent blood clots. But researchers observed no clear benefit to taking daily aspirin with a DOAC. Clotting events between the two groups were similar.

This was an observational study limited to people in Michigan. Study authors caution there are different subgroups and clinical scenarios where this has not been sufficiently studied.

A 2019 study published in JAMA Internal Medicine suggests that the combination of daily aspirin and warfarin is also associated with excess bleeding.

Dr. Michael Chan is an interventional cardiologist with Providence St. Joseph Hospital in Orange County, California.

He noted that one-third of participants in the study were taking aspirin "without a well-defined therapeutic indication."

"In those patients, they are likely increasing risk of bleeding without associated benefit," Chan told Healthline.

Aspirin is a nonsteroidal anti-inflammatory drug (NSAID). You can get it without a prescription, but that doesn't mean it can't cause problems.

Taking aspirin to help reduce inflammation, pain, and fever is one thing. Taking it every day is another. Aspirin is also a blood thinner, so it reduces the blood's ability to clot.

For some people, that's a good thing.

"Low-dose aspirin is currently recommended to prevent new cardiovascular events in patients with known atherosclerotic vascular disease," Chan said.

"This includes people with recent or prior heart attacks, history of acute occlusive strokes, peripheral artery disease, or chronic ischemic heart disease, such as those with prior coronary stents or coronary artery bypass surgery," he added.

Doctors may recommend low-dose aspirin in addition to a blood thinner if there's sufficient benefit to do so, Chan noted.

"The typical reasons that may occur is in patients with known coronary artery disease, such as those with a history of heart attacks, coronary stents, or coronary artery bypass surgery," Chan said.

"In appropriately selected patients, low-dose aspirin reduces the risk for heart attack or stroke. In patients with recent coronary artery stents, it reduces the risk of the stent abruptly clotting and is widely recommended in this setting," he continued.

For other people, taking two blood thinners is not a good idea.

"For my patients, I often reduce the aspirin dosing to 81 milligrams every other day, or three times a week (such as every Monday, Wednesday, and Friday) when used with full anticoagulation such as warfarin or the NOACs (novel oral anticoagulants) such as Eliquis, Xarelto, or Pradaxa to help reduce the bleeding risk," Chan said.

He advises people to follow their doctor's recommendations.

"They will help find the most suitable medical regimen that maximizes benefits while minimizing risks," he said.

People concerned about COVID-19 vaccines and blood clots, a rare adverse event, should speak with their doctor rather than start taking aspirin.

"There is no good clinical evidence to recommend starting low-dose aspirin to prevent what has been reported to be very rare blood clots associated with some COVID vaccines," Chan said.

"For those patients whose doctors have recommended they stay on low-dose aspirin, it is not recommended to stop it for a COVID vaccine. Patients may experience increased bruising at the site of injection but, in general, this should be mild," he added.