Blood thinners may be taken via mouth, vein, or skin to prevent blot clots, which might cause a heart attack or stroke. But, they may have serious side effects, especially if taken with other medications.

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Blood clots can stop blood flow to the heart, lungs, or brain. To prevent this, you may need to take blood-thinning medications.

It’s important to take them exactly as directed. When you don’t take enough, the medication won’t be as effective. Taking too much can lead to severe bleeding.

Read on to learn about how they work, who should take them, what side effects may occur, and any natural remedies you can also use.

Some medications work by thinning the blood to keep blood cells from sticking together in the veins and arteries. Others prevent blood clots by increasing the amount of time it takes for blood clots to form. These are known as anticoagulant and antiplatelet drugs, respectively.

Doctors often prescribe anticoagulants to people who have been diagnosed with some form of heart disease. “Coagulate” is a medical term that means “to clot.” These blood thinners prevent blood clots by increasing the amount of time it takes your blood to clot.

Anticoagulants prevent clots from forming. Common anticoagulant blood thinners include:

Newer anticoagulants with less chance of bleeding complications include:

On the other hand, antiplatelet drugs prevent blood cells (called platelets) from clumping together and forming clots. Examples of antiplatelet drugs are:

  • aspirin
  • clopidogrel (Plavix)
  • dipyridamole (Persantine)
  • ticlopidine (Ticlid)

Note, however, that you should not mix antiplatelet and anticoagulant drugs together. Particularly, you should avoid taking aspirin if taking an anticoagulant drug.

Your doctor will determine what blood-thinning medication is best for you. They will carefully monitor your dosage and may occasionally run a prothrombin time (PT) test. This blood test measures your international normalized ratio (INR).

INR is the rate at which your blood clots. An appropriate INR rate varies from person to person according to their medical history. Staying within your INR range can prevent you from bleeding excessively or clotting too easily.

Both anticoagulant and anti-platelet drugs are used to prevent a blood clot from forming. Another class of medications called thrombolytics may be used to dissolve a blood clot that has already formed, such as in the case of deep vein thrombosis (DVT) or pulmonary embolism, for example. The way these drugs work is also referred to as fibrinolytic therapy.

Blood thinners may cause side effects in some people. Excessive bleeding is the most common reaction. It can occur in a variety of ways, including:

  • heavy periods
  • bloody or discolored urine or feces
  • nosebleeds
  • bleeding gums
  • prolonged bleeding from a cut

Other side effects can include:

  • dizziness
  • muscle weakness
  • hair loss
  • rashes

The presence of blood thinners in your system can increase your chance of internal bleeding after an injury. Go to the hospital immediately if you experience any of these side effects after falling or bumping your head — even if you don’t have external bleeding.

Your doctor may tell you to limit your participation in contact sports to reduce the chance of bleeding. However, this doesn’t mean you can’t exercise or live your day-to-day life. Swimming, walking, and jogging are excellent forms of exercise and are safe for most people taking anticoagulants. Discuss with your doctor which types of exercise may be best for you.

Tell your dentist you’re taking blood thinners to avoid excessive bleeding during regular teeth cleanings. It’s also important to protect yourself when using knives, scissors, or yard equipment.

Thrombolytics can also cause excessive bleeding from the administration site or the area where the clot is sitting. Potential complications can include:

  • blood in the urine or stool
  • nosebleed
  • abnormally heavy or unusual vaginal bleeding
  • stroke

The blood clot may also break into pieces. The pieces may then travel to other body parts and cause more problems.

Various foods, herbs, and medications can interfere with blood thinners. These substances can make the drug more or less effective than your dosage would suggest.

However, not all blood thinners are affected by the same substances. It’s important to speak with your doctor or cardiologist about your diet and how it may impact the effectiveness of your medication.

Vitamin K

Vitamin K can lessen the effectiveness of some anticoagulants, such as warfarin. Depending on the particular medication you’re taking, you may still be able to eat foods with low-to-moderate levels of vitamin K. However, you should avoid eating certain foods that contain moderate-to-high levels of vitamin K. These include:

  • cabbage
  • brussels sprouts
  • broccoli
  • asparagus
  • endive
  • kale
  • lettuce
  • spinach
  • mustard greens
  • turnip greens
  • collard greens


People who take anticoagulant medications should use herbal supplements and teas with caution. Several herbs interfere with the anticlotting abilities of blood thinners. They can also increase your risk of bleeding and the amount of time you bleed.

Talk with your doctor before using any herbal supplement or tea, especially the following:

Alcoholic beverages and cranberry juice can contribute to the development of side effects when using blood thinners. Avoid these items as much as possible.


Take prescription and over-the-counter medications with caution when you’re using blood thinners. Many medications can increase your chance of bleeding excessively if you take them with blood thinning medications.

Several antibiotics, antifungal drugs, blood pressure medications, and antidepressants can increase your chance of bleeding. This also includes nonsteroidal anti-inflammatory drugs (NSAIDs) such as Ibuprofen (Advil, Motrin) or Naproxen (Aleve). Make sure to tell your doctor about all the medications you’re taking.

Taking over-the-counter bismuth subsalicylate (Pepto Bismol and others) can also increase bleeding with blood thinners because it falls into the same medication category as aspirin.

In addition, taking certain thrombolytic medications with ACE inhibitors may increase your chance of developing angioedema. Combining these drugs with antiplatelet or anticoagulant drugs may also increase your bleeding chance.

Many of the herbs that may interact with blood-thinning medications do so because they, too, have either antiplatelet or anticoagulant properties.

Check with your doctor before eating these foods if you’re taking a blood-thinning medication because they could thin your blood too much.

In addition, foods rich in vitamin E are natural blood thinners. Several oils contain vitamin E, such as olive, corn, soybean, and wheat germ. Other food sources of vitamin E include:

  • spinach
  • tomatoes
  • mangoes
  • kiwis
  • peanut butter
  • almonds
  • sunflower seeds
  • broccoli

Natural anticoagulants can benefit your heart health, but consume them with caution.

Blood clots can be dangerous because they interfere with blood flow to your vital organs. If you have issues with your heart, you may have a greater chance of developing blood clots and may need to take blood-thinning medications.

These drugs work by either thinning your blood or raising the time it takes for blood clots to form. However, they may have some side effects.

It’s important to take them exactly as your doctor instructs and avoid certain foods or other medications that can make them less effective.