AFib: Long-Term Blood Thinner Use

Medically Reviewed by Jabeen Begum, MD on February 20, 2023
6 min read

If you have atrial fibrillation (AFib), your doctor may suggest long-term blood thinners, also called anticoagulants. They lower your risk for stroke caused by a blood clot, the most dangerous complication of AFib.

Your doctor will use a formula to find out how high your risk of stroke is. With AFib, your risk of stroke can be up to five times higher than people who don’t have it. The higher your stroke risk, the more blood thinners may help you.

But blood thinners also have risks. Sometimes, they can cause bleeding, though it’s usually minor. Your doctor will estimate your risk for this complication. That will help you and your doctor decide whether your risk of stroke outweighs your risk of dangerous bleeding.

For most people with AFib, the benefits of blood thinners are greater than their risks.

Your fast, out-of-sync heartbeat with AFib makes it harder for your heart to squeeze, or contract, strongly. This slows down its pumping action, which can cause blood to pool in your heart’s upper chamber and form clots.

When your heart pumps out the clots, they can move to your brain. There, they can block an artery and cause you to have a stroke. The clots also can travel to other parts of your body, such as your legs or kidneys, where they can cut off your blood flow and damage your nearby tissue. Clots are the most common cause of stroke.

Despite their name, blood thinners don’t really thin your blood. They make it harder for it to clot. And while they can’t break up clots you have already, they can stop them from growing.

On average, blood thinners reduce your risk of an AFib-related stroke by more than 50%.

Your doctor will probably use a formula called CHA2DS2-VASc to add up your stroke risk score. Your score is based on how many stroke risk factors you have. These include your age and other health conditions.

You get 1 or 2 points for each risk factor you have. The higher your score, the more likely you are to have a stroke. These risk factors include:

  • Congestive heart failure = 1 point
  • High blood pressure = 1 point
  • Age (older than 75 years) = 2 points
  • Age (65 to 74 years) = 1
  • Diabetes (type 2) = 1 point
  • Prior stroke or mini-stroke = 2
  • Vascular disease, such as a heart attack or peripheral artery disease = 1
  • Sex (female) = 1

If you score 0 and you’re a man, or 1 and you’re a woman, your stroke risk is low. Your doctor may want you to take a blood thinner for a few weeks before and after you have an AFib treatment called cardioversion.

Cardioversion delivers an electrical shock to your heart that can bring it back into a normal rhythm. If it works for you, you may not need to take a blood thinner long-term.

If you score 2 or more points and you're a man, or 3 or more points and you’re a woman, you’re at medium to high risk of stroke. Your doctor will probably suggest long-term blood thinner treatment. This is true for all types of AFib, including paroxysmal, persistent, and permanent AFib.

There are two types of blood thinners: direct oral anticoagulants (DOACs) and warfarin. Unless there's a reason you shouldn’t take them, your doctor will probably prescribe DOACs.

DOACs: These newer blood thinners block a protein that helps form blood clots. DOACs may work better than warfarin to prevent blood clots. They also cause fewer dangerous bleeding problems, such as bleeding in the brain.

Unlike warfarin, DOACs don’t interact with a lot of other drugs or with most foods. One drawback is the cost, which is higher than that of warfarin.

These drugs include:

  • Apixaban (Eliquis)
  • Dabigatran (Pradaxa)
  • Edoxaban (Savaysa)
  • Rivaroxaban (Xarelto)

Warfarin: This older blood thinner blocks vitamin K, which helps your blood clot. If you take warfarin, your doctor will check your blood regularly. This is to make sure your dose stays in a sweet spot that keeps your blood from clotting too fast or too slow.

You and your doctor may chose warfarin instead of a DOAC if:

  • You have a mechanical heart valve
  • You have severe chronic kidney disease
  • The cost of DOACs is too high

Studies show that the latest drugs work as well as warfarin. But trying to figure out how the new medicines compare to each other is a bit trickier. There isn’t any research that compares them head to head.

"We can't rank the new ones from one to four," says Richard Kovacs, MD, clinical director of the Krannert Institute of Cardiology at Indiana University. "We don't have enough data to suggest one of them over another."

Bleeding is the biggest risk of blood thinners. The risk varies from person to person. It's less likely with the newer medications. And since they wear off faster than warfarin, bleeding problems may not be as serious when they happen. Your risk of bleeding, which your doctor will estimate before you start blood thinners, may be higher if you:

  • Have liver or kidney problems
  • Have already had serious bleeding
  • Take drugs like aspirin and other NSAIDs that can raise your risk of bleeding
  • Drink a lot of alcohol

If bleeding does happen, it’s usually minor. It may take longer for you to stop bleeding if you cut yourself, for example. You may also have nosebleeds, or you might bruise more easily. Usually, your doctor can manage these kinds of bleeding.

It’s rare, but blood thinners also can cause the sorts of bleeding that can kill you. This includes bleeding in your brain, bowels, or stomach. Symptoms of a life-threatening bleed include:

  • Vomiting blood
  • Bloody, dark, or black poop
  • A sudden, severe headache

Call 911 if you take blood thinners and have any of these symptoms.

They may be more convenient because you don't need as many blood tests. With warfarin, you need testing at least once a month to make sure it's working right.

Also, with warfarin, you need to be consistent with how much vitamin K is in your diet. Vitamin K is a nutrient in a lot of leafy green vegetables, and it affects how well warfarin works. You can still enjoy those foods, but if you vary how much of them you eat, it will affect your dose. 

That's not an issue with the newer medications. Vitamin K doesn't interfere with how they work.

Some prescription and over-the-counter drugs make it harder for warfarin to work. Others make the medicine work too well and raise your risk of bleeding.

Many medications can interact with warfarin, which can be a problem if you need to treat another condition. 

The newer blood thinners don't mix well with some drugs. But that's far less likely than with warfarin.  

Stay on warfarin if you have kidney failure or if you have mechanical heart valves. The new meds may not be safe for those situations.

What's more, if the old standby works well for you, your doctor might not suggest a change.

"If you've been on warfarin, you're stable, don't have bleeding problems, and don't mind going to the laboratory," Kovacs says, "in my opinion, there's generally not a compelling reason to switch."

A left atrial appendage (LAA) device can lower your risk of stroke without the long-term use of blood thinners.

If your doctor thinks an LAA procedure is right for you, they can place a small device in your left atrial appendage. This is an area of your heart where blood tends to pool. Your doctor can place the device by making only a few small cuts, or incisions, in your body.

Weight loss may help with health risks linked to AFib if you have obesity. 

No matter what AFib treatments you’ve had,  even if you no longer have AFib symptoms, always check with your doctor before you stop taking blood thinners.