Anticoagulants and antiplatelet drugs are commonly called blood thinners. These powerful medicines reduce the blood's ability to form clots. Some people with conditions such as atrial fibrillation, heart failure, or heart valve problems may take them because of their increased risk of blood clots.
A blood clot that forms on the outside of the body over a wound is a good thing. It stops the bleeding if you cut yourself. But a blood clot that forms inside a blood vessel can cut off blood flow to vital organs like the brain or heart. This results in a stroke or heart attack. A clot can also block circulation in the legs or lungs.
If taken properly, blood thinners can help prevent dangerous clots but still allow normal clotting to take place and stop blood flow from an injury.
Examples of blood thinners are:
A newer drug called Pradaxa (dabigatran etexilate) may also be an option to prevent stroke in some people with atrial fibrillation. Regular blood test monitoring is not required with Pradaxa as it is with warfarin.
To make sure your blood thinner medication is both safe and effective, follow these steps.
1. Timing is important
- Take your blood thinner at the same time each day.
- Never skip a dose or take more than your prescribed dose.
- If you miss a dose, take the medicine as soon as you remember.
- If you don't remember until the next day, call your doctor for instructions before taking that day's dose.
You may find it easier to take your medicine if you use a pill organizer with compartments for each day of the week.
A head injury can result in bleeding within the brain. This can cause a severe headache or other signs of a stroke.
Call 9-1-1 if you are on a blood thinner and you have:
- A severe headache
- A fall or injury to the head
- Confusion, numbness, weakness
- Coughed up large amounts of bright red blood
- Vomited blood
- Passed a lot of blood in the stool
Bleeding from the digestive track can occur gradually over time and may not cause pain. Seek immediate medical help if you have any of the following:
- Bright red blood in the stool
- Very dark or black stool
- Blood in the urine
- Bleeding that does not stop
- Bleeding in the mouth after a dental procedure
3. Use caution
Be careful with:
- New prescription medicine. Any doctor you see should know that you are taking a blood thinner. Coumadin and other blood thinners can interact with many types of medicine.
- Over-the-counter products. Check with your doctor or pharmacist before taking any non-prescription product, including aspirin, herbal medicine, or vitamins.
- Alcohol. Alcohol increases the effect of blood thinners and raises the risk of bleeding.
- Foods containing vitamin K. Foods that contain vitamin K can interfere with blood thinners. They make warfarin less effective and raise the risk of a blood clot. Vitamin K is found in green and leafy vegetables such as broccoli, lettuce, and spinach. You don't have to avoid these foods, but keep the amount of vitamin K you eat consistent from day to day.
- Dental visits. Tell your dentist that you are taking a blood-thinning medicine as well as about all your other medicines. He or she may modify certain dental procedures to limit bleeding. Avoid eating hard foods or foods with sharp surfaces for 2 days after a dental procedure.
4. Keep your lab appointments
Doctor visits for blood tests or lab visits are important when you are on certain blood thinners such as warfarin. Frequent testing is often needed to make adjustments to this medicine.
While taking warfarin, a blood test is used to measure the time it takes blood to clot. It's called the prothombin time, or "protime." The result is reported as the INR, which stands for the International Normalized Ratio. The INR is what your doctor uses to monitor the effects of the drug. The goal is to take enough blood thinner to keep the INR in the therapeutic range, which is higher than normal so that clotting is delayed but not prevented.
- When the INR is too low, the risk of a dangerous blood clot is increased.
- When it is too high, the risk of bleeding is increased.
It often takes some time to get the INR into the therapeutic range. INR monitoring may be necessary twice a week or more at first, and then less frequently.
- American Academy of Oral Medicine. Patient information sheet: blood thinners and dental care. Accessed: 03/22/2011
- American Heart Association. What are anticoagulants and antiplatelet agents? Accessed: 03/22/2011
- Agency for Healthcare Research and Quality. Blood thinner pills: your guide to using them safely. Accessed: 03/22/2011
- U.S. Food and Drug Administration. FDA approves Pradaxa to prevent stroke in people with atrial fibrillation. Accessed: 03/22/2011
- National Institutes of Health. Important information to know when you are taking: Coumadin and vitamin K. Accessed: 03/22/2011
- Fiumara K, Goldhaber SZ. A patient's guide to taking Coumadin/warfarin. Circulation. 2009;119:e220-e222.