Uses, Types, Side Effects, Interactions


Blood thinners are a class of medications that help prevent blot clots from forming in an artery (a type of blood vessel). Healthcare providers prescribe these medications to lower the risk of developing blood clots and treat a wide range of cardiovascular diseases including, heart attacks and strokes. If your healthcare provider recommends a blood thinner for you, you may take it orally as a pill or inject it into your body.

You might think that blood thinners make your blood thinner—but that’s not exactly the case. Instead, they work by managing blood coagulation, a natural body process that prevents excessive bleeding when you get injured.

During normal blood coagulation, blood cells like platelets and other proteins work to create blood clots over an injured area to stop the bleeding. These blood clots then dissolve after your injury heals. But sometimes, blood clots can form inside of your blood vessels and do not dissolve naturally. These abnormal clots are a significant health concern because they can disrupt proper blood flow and are often the main cause of several heart diseases.

Blood thinners prevent blood clots by stopping the activity of proteins that regulate blood clot formation. Additionally, some blood thinners prevent blood clot formation by preventing the accumulation of platelets, which are important blood cells that play a role in blood clotting.

It’s worth noting that blood thinners aren’t meant to completely stop the blood coagulation process because this process is required to heal wounds properly. Instead, these medications are meant to slow the coagulating process enough to prevent abnormal blood clots from forming.

Your healthcare provider may prescribe blood thinners to treat these conditions:

In some cases, your provider may also recommend taking blood thinners after a heart attack or stroke to prevent another one from occurring. Keep in mind: blood thinners can interact with many other medications and some diets. When taking blood thinners, it is important to follow your prescription directions very carefully. Your provider may also perform regular blood tests to monitor how well your blood is clotting while you’re taking these medications.

There are several types of blood thinners, and each is categorized by how they prevent blood clots from forming.

Vitamin K Antagonists

Vitamin K antagonists are some of the most commonly prescribed blood thinner medications. They prevent blood clots from forming by blocking the activity of blood clot proteins in the liver from interacting and producing vitamin K. This vitamin is an essential component for blood coagulation. The reduction of vitamin K in the bloodstream slows down the coagulation process, preventing blood clots from forming.

Usually, it takes vitamin K antagonists about two to four days to take effect. These medications are often most helpful in preventing strokes and atrial fibrillation (a type of irregular heartbeat). Common vitamin K antagonists include Jantoven (warfarin) and Marcumar (phenprocoumon).

Direct Oral Anticoagulants

Direct oral anticoagulants are newer anticoagulation medications that can treat and prevent stroke, atrial fibrillation, deep vein thrombosis, and other cardiovascular (heart-related) conditions. These medications work by inhibiting factor Xa, a protein that plays a major role in blood-controlling coagulation. Some of the commonly prescribed direct oral anticoagulants are Eliquis (apixaban), Xarelto (rivaroxaban), and Savaysa (edoxaban).

These types of blood thinners act fast. In fact, their anticoagulating effects happen within four hours of taking the medication. Direct oral anticoagulants require less blood monitoring than traditional blood thinner medications and they do not cause potential dietary changes. These medications have also been shown to have fewer harmful drug interactions with other medications as compared to other blood thinners.


Heparins are anticoagulants that can help treat and prevent deep vein thrombosis, pulmonary embolism, and atrial fibrillation. These medications work by binding to antithrombin (a protein that is essential to the coagulating process) and slow down the blood clotting process. Some examples of heparins include Lovenox (enoxaparin) and Fragmin (dalteparin).

Keep in mind: heparins can also help prevent excessive blood clotting during medical procedures like cardiac surgeries and dialysis. Because heparins can work faster than other blood thinners, healthcare providers use these during medical procedures to prevent or stop any serious symptoms if a blood clot occurs.


Antiplatelet drugs are anticoagulants that work by making platelets less likely to stick to each other in your blood vessels. Preventing platelets from sticking to each other helps lower the risk of developing blood clots in your arteries. These medications are sometimes also known as platelet aggregation inhibitors.

Healthcare providers prescribe antiplatelets to people who are at a higher risk of getting a heart attack or have previously experienced a heart attack or stroke. These medications can help reduce the likelihood of having another cardiovascular event. Aspirin (acetylsalicylic acid) is the most common antiplatelet drug. Other common medications include Plavix (clopidogrel), Effient (prasugrel), and Persantine (dipyridamole).

You can take blood thinners orally as tablets or pills. They can also be administered via injection subdermally (under the skin), subcutaneously (in the fatty tissue layer between the skin and the muscle), or intravenously (in the vein). Vitamin K antagonists, direct oral anticoagulants, and antiplatelets are prescribed as tablets, while heparins are only given via an injection.

The most common side effect of blood thinners is experiencing excessive bleeding. Because blood thinners affect the body’s ability to coagulate blood, it’ll take your body longer to stop bleeding and heal wounds after injuries like a cut or a scrape.

Other side effects include:

Blood thinners are medications that require close monitoring, so it’s important to follow the directions of your medication properly. When you take blood thinners, you may have regularly scheduled blood tests to monitor how well your blood is clotting.

During these appointments, you should keep your healthcare provider updated on other medications you’re taking. Blood thinners can have interactions with other medications which can potentially be dangerous. Some medications that have been shown to have harmful drug interactions when taken alongside blood thinners include:

People who are pregnant or are planning to become pregnant need to discuss this with their healthcare provider taking blood thinners. Vitamin K antagonists may negatively affect the child during pregnancy if the medication crosses the placenta. Vitamin K antagonists should also be avoided during breastfeeding to prevent the medication from passing on to the child through breast milk and affecting the child’s blood.

Diet can also affect how some blood thinners work. Because vitamin K antagonists work by reducing vitamin K in the bloodstream, the amount of vitamin K you consume in your diet may affect your medication. Your healthcare provider should discuss some potential diet changes that you might need to consider while taking a vitamin K antagonist blood thinner.

Finally, your medical history also affects if blood thinners are right for you. Some of the medical conditions or situations that might prevent you from taking blood thinners are recent surgery or a history of intracranial hemorrhage (brain bleed).

It’s important to take blood thinners as prescribed. If you are taking blood thinners, keep in contact with your healthcare provider to regularly review your dosage, medication schedule, and any side effects you’re experiencing. You should contact your healthcare provider immediately if you have any signs of serious bleeding or experience any of the following symptoms:

  • Abnormal menstrual bleeding
  • Red or brown-colored urine or vomit
  • Black-colored stools
  • Nosebleeds
  • Bleeding in your gums
  • Injuries like cuts or scrapes that do not heal
  • Coughing up blood
  • Unusual bruising
  • Dizziness

Blood thinners are a class of medications that help prevent blot clots from forming and are used to treat a variety of cardiovascular (heart) diseases including heart attacks, strokes, and deep vein thrombosis. Blood thinners work by slowing down your blood clotting process. There are several types of blood thinner medications and it’s important to follow your treatment plan as described. If you experience any side effects (like changes in urine color), contact your healthcare provider for support—as they may change your dosage or medication to better suit your needs.


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