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People take blood thinners to prevent the formation of blood clots and reduce their risk of heart attack, stroke, and pulmonary embolism.

Blood clots can cause different types of heart disease. People can also develop heart disease if they have atherosclerosis, which is a buildup of fatty deposits in the arteries.

Blood clots can partially or completely block a blood vessel. They can form anywhere in the body but are more common in certain areas. The area where they develop will determine the severity of the risk that they pose.

If a person has a blood clot in the blood vessels leading to the brain, they can have a stroke, while a blood clot in the blood vessels around the heart can result in a heart attack. People with atrial fibrillation are also at risk of stroke due to blood clots developing in the heart.

Doctors use the term pulmonary embolism to refer to a blood clot in a major blood vessel in the lungs. They call a blood clot in the legs a deep vein thrombosis (DVT). A DVT can dislodge and move up to the lungs, causing a pulmonary embolism.

Blood thinners act on different parts of the clotting pathway that can lead to blood clots. Doctors use specific blood thinners that block factors that cause blood clots.

People with clots in their arteries due to a platelet plug — the stage before a thrombosis forms — may require a different type of blood thinner that acts on particular blood cells, such as platelets.

Below, we cover the different types of blood thinners for heart disease.

Today, doctors can choose from many different blood thinners. They will select the most appropriate blood thinner depending on their evaluation of the person, which is likely to take into account:

• the person’s family and personal medical history
• their risk factors for developing blood clots
• the location of the blood clot
• whether it is the person’s first blood clot
• the severity of the blockage

There are two categories of blood thinners: antiplatelets and anticoagulants.

Antiplatelets

A person may receive injectable, intravenous, or oral antiplatelet medications. Antiplatelet medications that people take orally include:

• aspirin
• clopidogrel (Plavix)
• ticagrelor (Brilinta)
• prasugrel (Effient)
• pentoxifylline (Trental)
• cilostazol (Pletal)
• dipyridamole (Persantine)

The injectable or intravenous antiplatelet drugs include:

• tirofiban (Aggrastat)
• eptifibatide (Integrilin)

Anticoagulants

In some situations, doctors will prescribe anticoagulants. There are three classes of anticoagulants:

• heparin and low molecular weight heparin
• vitamin K antagonists, such as warfarin
• newer direct oral anticoagulants

The following table lists the drugs in these categories.

Blood clotting is a complex process that depends on many factors. Warfarin works by preventing vitamin K-dependent clotting factors from forming.

Newer direct oral anticoagulants inhibit other factors, such as factor Xa or an enzyme called thrombin, both in the blood and in existing clots.

Heparins also inactivate thrombin, which helps treat clots and prevent new ones from forming.

People who take blood thinners are at an increased risk of excessive bleeding. If they cut themselves, it may take longer for the bleeding to stop. Sometimes, bleeding may require medical attention.

The most common side effects of antiplatelet medications include:

• easy bruising
• nosebleeds
• blood in the urine
• hemorrhage or large bleeds
• bleeding in the stomach
• breathing difficulty due to ticagrelor
• low blood platelet count
• aspirin-induced asthma
• nasal polyps

Warfarin can also cause bleeding, which can occasionally be severe. Some people can experience major bleeds in the brain, eyes, and digestive tract.

Other side effects of warfarin include:

• nausea
• vomiting
• stomach pain
• bloating
• flatulence (gas)
• change in the sense of taste

If a person experiences dangerous bleeding from warfarin, doctors can reverse the drug’s action by giving them intravenous vitamin K and fresh frozen plasma or prothrombin complex concentrate.

Newer direct oral anticoagulants have an association with lower rates of major bleeds, including life threatening bleeding and bleeding into the brain.

The newer direct oral anticoagulants also have commercially available medicines to reverse their actions.

If people experience heavy bleeding or hemorrhage, doctors will stop giving them the drug and provide protamine sulfate, which inactivates heparin.

Other side effects that may occur when using heparin are:

• low blood platelet count
• osteoporosis
• fractures
• low levels of aldosterone, a hormone that regulates salt and water in the body
• allergic reactions

People taking blood thinners should let their doctors know about any other medications that they are taking. Some blood thinners also interact with certain foods.

In general, combining blood thinners with other drugs that cause bleeding further increases a person’s risk of bleeding.

Antiplatelet medications

Other substances that may interact with aspirin or antiplatelet medications include:

• diuretics
• nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen (Advil)
• steroid drugs
• alcohol

As well as interacting with other drugs that thin the blood, Plavix and Effient may interact with opioids. Plavix also interacts with omeprazole (Prilosec), which reduces stomach acid.

Brilinta can interact with digoxin (Lanoxin) and with high doses of simvastatin (Zocor) and lovastatin (Altoprev).

A doctor will closely monitor people who take blood thinners.

Warfarin

Doctors who prescribe warfarin must warn the person about the many drug and food interactions that occur with this anticoagulant.

Some substances that interact with warfarin include:

• antibiotics
• antifungals
• botanical or herbal products
• other anticoagulants and antiplatelet agents
• foods containing vitamin K

People need to do frequent blood tests when taking warfarin. Doctors will use the blood test to check a person’s International Normalized Ratio (INR).

The INR test provides important information to help doctors determine the appropriate dosage of warfarin. Drug and food interactions can cause changes in a person’s INR.

An INR reading that is too low puts people at risk of clotting, whereas a reading that is too high indicates an increased risk of bleeding. The correct reading for someone on anticoagulants is 2–3.

Doctors may also tell people taking warfarin to pay attention to the vitamin K content in the foods that they eat. People taking warfarin should not avoid vitamin K altogether, but they may need to limit their intake of it.

Learn more about vitamin K, diet, and warfarin in this article.

Heparin

Anyone who takes heparin or low molecular weight heparin should avoid any drugs that increase the risk of major bleeding.

If someone requires other blood thinners while taking heparin, doctors will need to monitor the person closely for signs of bleeding.

Newer direct oral anticoagulants

Compared with warfarin, newer direct oral anticoagulants have fewer drug interactions and may be safer options, although more, long-term clinical use is necessary to confirm this.

These drugs also do not require people to make dietary changes or have INR monitoring. Researchers note, however, that newer direct oral anticoagulants may be more expensive than warfarin for many people.

Some foods and supplements have blood-thinning effects. People who need to take prescription blood-thinning medications should limit or avoid these foods and supplements, which may increase their risk of bleeding.

The following supplements and foods may thin the blood:

Blood thinners include antiplatelet and anticoagulant medications. People who have a blood clot or a higher risk of developing one may need to take one or more blood thinners to prevent problems, which can include:

• a heart attack
• a stroke
• pulmonary embolism

Doctors and pharmacists must explain the risks of taking blood thinners, including the possible drug and food interactions, to prevent excessive bleeding.

Many natural and over-the-counter products can thin the blood and increase a person’s risk of bleeding.

Newer oral direct anticoagulants may be safer alternatives to warfarin as they have fewer drug interactions. Some people find that they also cause fewer side effects.