What Are the Types of Anticoagulants?

Medically Reviewed by Jennifer Robinson, MD on March 21, 2024
3 min read

Anticoagulants are medications that help stop your blood from thickening or “clotting.” Your body does need to be able to clot to help seal wounds inside and outside your body. But unnecessary clots can cause problems that can be life-threatening. Those that travel to the brain can cause a stroke; to the heart, cardiac arrest; and to the lungs, a pulmonary embolism.

Though sometimes called “blood thinners,” anticoagulants don’t actually thin your blood. They simply interrupt your body’s natural clotting process. Different drugs act on different parts of this clotting process.

There are three main types of anticoagulant medications:

  • Vitamin K antagonists
  • Direct Oral Anticoagulants (DOACs)
  • Low molecular weight heparins (LMWH)

Each type works in a different way to prevent unneeded blood clots.

Vitamin K helps your blood clot. You get it from green leafy vegetables like broccoli and spinach and from the action of bacteria in your gut. Vitamin K “antagonists” like warfarin stop your liver from processing vitamin K into “factors” that normally help clot your blood. This curbs blood clotting.

If you take this type of medication, it’s important to keep the amount of vitamin K in your diet fairly consistent so that your doctor can estimate the right dose of warfarin from day to day and week to week. You’ll get blood tests so your doctor can track the effects of your dose and your diet. Your doctor will likely use the international ratio test, or INR, to check on how well your blood can clot.

One of the potential advantages of this type of anticoagulant is that it’s easier than others to reverse in case you have sudden bleeding from trauma or emergency surgery.

DOACs work more quickly than vitamin K antagonists, which have been around longer. DOACs can also be more predictable. So you may not need to take blood tests and be careful about how much vitamin K you eat and drink. On the other hand, these drugs tend to work for shorter periods, so you may need to take them twice a day, compared to once daily for other anticoagulants.

DOACs include:

Direct thrombin inhibitors: These drugs interfere with your body’s use of thrombin, a key enzyme that helps clot your blood. Though it's typically injected in a vein, you can take it in pill form as dabigatran (Pradaxa).

Direct factor Xa inhibitors: This type of anticoagulant stops the Xa factor in the clotting process from working as it should. These medications, which come in pill form, include apixaban (Eliquis), dabigatran (Pradaxa), edoxaban  (Savaysa), and rivaroxaban (Xarelto).

You might know these drugs as dalteparin (Fragmin) or enoxaparin (Lovenox).

Compared to regular unfractionated heparin (UFH), which is typically used in hospitals, LMWH is more predictable and longer-lasting, which means your doctor doesn’t need to track its effects as closely as with other anticoagulants like warfarin and UFH.

Doctors prescribe a fixed dose based on your body weight. You inject this medication under your skin.

LMWH is often used as a bridge to long-term use of oral anticoagulants such as warfarin. You might take both for a while as your doctor closely follows how you’re doing on these medications. Then, once your blood levels of warfarin are high enough, you stop the shots of LMWH.

Tell your doctor about any nonsteroidal anti-inflammatories (NSAIDs) that you take, as these can raise your risk of bleeding if you also take heparin. NSAIDs are pain relievers that include aspirin, ibuprofen, and naproxen.