Blood Thinner Pills: Your Guide to Using Them Safely

The Agency for Healthcare Research and Quality offers a free booklet and a video about blood thinner medicines. Staying Active and Healthy with Blood Thinners, a 10-minute video, features easy-to-understand explanations of how blood thinners work and why it's important to take them correctly. Blood Thinner Pills: Your Guide to Using Them Safely, a 24-page booklet, explains how these pills can help prevent dangerous blood clots from forming and what to expect when taking these medicines.

Video—Staying Active and Healthy with Blood Thinners

People often worry about how routine medicines like blood thinner pills will affect their lifestyles. With a few simple steps, taking a blood thinner can be safe and easy. In fact, more than 2 million people take blood thinners every day to keep them from developing dangerous blood clots. Staying Active and Healthy with Blood Thinners is a 10-minute video that shows how small changes in daily routines can help people take blood thinners safely.

What is a blood thinner? What does it do? Why it is helpful? These questions are answered in this video, which features easy-to-understand explanations of how blood thinners work and why it's important to take them correctly. It also introduces BEST, an easy way to remember how to fit blood thinner medication into daily life.

Be Careful
Eat Right
Stick to a Routine
Test Regularly

How to Order a Copy of the Video

Copies of this video on DVD can be ordered from the AHRQ Publication Clearinghouse by calling 800-358-9295 or sending an E-mail to
Ask for AHRQ Publication Number 09-0086-DVD.

Booklet—Blood Thinner Pills: Your Guide to Using Them Safely

Blood Thinner Pills: Your Guide to Using Them Safely is an easy-to-read booklet that educates people about blood thinners. It offers basic information about the medication, including reasons why a clinician might prescribe it. It also includes tips on diet, medicines and foods to avoid, important precautions for some daily activities, and when to seek help.

Select to download print version of the guide [ PDF file PDF version - 2.43 MB ].

This guide is also available in Spanish [PDF file PDF version - 3.15 MB]. 


About Your Blood Thinner
How to Take Your Blood Thinner
Check Your Medicine
Using Other Medicines
Talk to Your Other Doctors
Possible Side Effects
Stay Safe While Taking Your Blood Thinner
Food and Your Blood Thinner
Blood Tests



About Your Blood Thinner

Your doctor has prescribed a medicine called a blood thinner to prevent blood clots. Blood clots can put you at risk for heart attack, stroke, and other serious medical problems. A blood thinner is a kind of drug called an anticoagulant (an-te-ko-AG-u-lent). "Anti" means against and "coagulant" means to thicken into a gel or solid.

Blood thinner drugs work well when they are used correctly. To help you learn about your medicine, your doctor has given you this booklet to read.

Depending on where you receive care, you may be seen by a doctor, nurse, physician’s assistant, nurse practitioner, pharmacist, or other health care professional. The term "doctor" is used in this booklet to refer to the person who helps you manage your blood thinner medicine.

You and your doctor will work together as a team to make sure that taking your blood thinner does not stop you from living well and safely. The information in this booklet will help you understand why you are taking a blood thinner and how to keep yourself healthy. Please take time to read all of the information in this booklet.

There are different types of blood thinners. The most common blood thinner that doctors prescribe is warfarin (Coumadin®, COU-mad-din). Your doctor may also discuss using one of the newer blood thinners depending on your individual situation.


Tell your doctor if you are pregnant or plan to get pregnant. Many blood thinners can cause birth defects or bleeding that may harm your unborn child.

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How to Take Your Blood Thinner

Always take your blood thinner as directed. For example, some blood thinners need to be taken at the same time of day, every day.

Never skip a dose, and never take a double dose.

If you miss a dose, take it as soon as you remember. If you don’t remember until the next day, call your doctor for instructions. If this happens when your doctor is not available, skip the missed dose and start again the next day. Mark the missed dose in a diary or on a calendar.

A pillbox with a slot for each day may help you keep track of your medicines.

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Check Your Medicine

Check your medicine when you get it from the pharmacy.

  • Does the medicine seem different from what your doctor prescribed or look different from what you expected?
  • Does your pill look different from what you used before?
  • Are the color, shape, and markings on the pill the same as what you were given before?

If something seems different, ask the pharmacist to double check it. Many medication errors are found by patients.

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Using Other Medicines

Tell your doctor about every medicine you take. The doctor needs to know about all your medicines, including medicines you used before you started taking a blood thinner.

Other medicines can change the way your blood thinner works. Your blood thinner can also change how other medicines work.

It is very important to talk with your doctor about all the medicines you take, including other prescription medicines, over-the-counter medicines, vitamins, and herbal products.

Products that contain aspirin may lessen the blood’s ability to form clots and may increase your risk of bleeding when you also are taking a blood thinner. If you are taking a blood thinner, talk to your doctor before taking any medication that has aspirin in it.

Medicines you get over the counter may also interact with your blood thinner. Following is a list of some common medicines that you should talk with your doctor or pharmacist about before using.

Pain relievers, cold medicines, or stomach remedies, such as:

  • Advil®
  • Aleve®
  • Alka-Seltzer®
  • Excedrin®
  • ex-lax®
  • Midol®
  • Motrin®
  • Nuprin®
  • Pamprin HB®
  • Pepto Bismol®
  • Sine-Off®
  • Tagamet HB®
  • Tylenol®

Vitamins and herbal products, such as:

  • Centrum®, One a Day®, or other multivitamins.
  • Garlic.
  • Ginkgo biloba.
  • Green tea.

Talk to your doctor about every medication and over-the-counter product that you take.

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Talk to Your Other Doctors

Because you take a blood thinner, you will be seen regularly by the doctor who prescribed the medicine. You may also see other doctors for different problems. When you see other doctors, it is very important that you tell them you are taking a blood thinner. You should also tell your dentist and the person who cleans your teeth.

If you use different pharmacies, make sure each pharmacist knows that you take a blood thinner.

Blood thinners can interact with medicines and treatments that other doctors might prescribe for you. If another doctor orders a new medicine for you, tell the doctor who ordered your blood thinner because dose changes for your blood thinner may be needed.

Tell all your doctors about every medication and over-the-counter product that you take.

Tell your doctor about all your medicines.

Always tell your doctor about all the medicines you are taking. Tell your doctor when you start taking new medicine, when you stop taking a medicine, and if the amount of medicine you are taking changes. When you visit your doctor, bring a list of current medicines, over-the-counter drugs—such as aspirin—and any vitamins and herbal products you take. A personal, medication wallet card can help you keep track of this list. Go to to download a printable wallet card that you can use to record the medicine and other products that you take.

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Possible Side Effects

When taking a blood thinner it is important to be aware of its possible side effects. Bleeding is the most common side effect.

Call your doctor immediately if you have any of the following signs of serious bleeding:

  • Menstrual bleeding that is much heavier than normal.
  • Red or brown urine.
  • Bowel movements that are red or look like tar.
  • Bleeding from the gums or nose that does not stop quickly.
  • Vomit that is brown or bright red.
  • Anything red in color that you cough up.
  • Severe pain, such as a headache or stomachache.
  • Unusual bruising.
  • A cut that does not stop bleeding.
  • A serious fall or bump on the head.
  • Dizziness or weakness.

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Stay Safe While Taking Your Blood Thinner

Call your doctor and go to the hospital immediately if you have had a fall or hit your head, even if you are not bleeding. You can be bleeding but not see any blood. For example, if you fall and hit your head, bleeding can occur inside your skull. Or, if you hurt your arm during a fall and then notice a large purple bruise, this means you are bleeding under your skin.

Because you are taking a blood thinner, you should try not to hurt yourself and cause bleeding. You need to be careful when you use knives, scissors, razors, or any sharp object that can make you bleed.

You also need to avoid activities and sports that could cause injury. Swimming and walking are safe activities.  If you would like to start a new activity that will increase the amount of exercise you get every day, talk to your doctor.

You can still do many things that you enjoy. If you like to work in the yard, you still can. Just be sure to wear sturdy shoes and gloves to protect yourself. If you like to ride your bike, be sure you wear a helmet.

Tell others.

Keep a current list of all the medicines you take. Ask your doctor about whether you should wear a medical alert bracelet or necklace. If you are badly injured and unable to speak, the bracelet lets health care workers know that you are taking a blood thinner.

To prevent injury indoors:

  • Be very careful using knives and scissors.
  • Use an electric razor.
  • Use a soft toothbrush.
  • Use waxed dental floss.
  • Do not use toothpicks.
  • Wear shoes or non-skid slippers in the house.
  • Be careful when you trim your toenails.
  • Do not trim corns or calluses yourself.

To prevent injury outdoors:

  • Always wear shoes.
  • Wear gloves when using sharp tools.
  • Avoid activities and sports that can easily hurt you.
  • Wear gardening gloves when doing yard work.

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Food and Your Blood Thinner

If your doctor has prescribed warfarin, the foods you eat can affect how well your blood thinner works for you. High amounts of vitamin K can work against warfarin. Other blood thinners are not affected by vitamin K. Ask your doctor if your diet can affect how well your blood thinner works.

For a list of foods that contain vitamin K, go to and search for vitamin K.

If you are taking a blood thinner, you should avoid drinking alcohol.

Call your doctor if you are unable to eat for several days, for whatever reason. Also call if you have stomach problems, vomiting, or diarrhea that lasts more than 1 day. These problems could affect your blood thinner dose.

Keep your diet the same.

Do not make any major changes in your diet or start a weight loss plan unless you talk to your doctor first.

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Blood Tests

You will have to have your blood tested often if you are taking warfarin. The blood test helps your doctor decide how much medicine you need.

The International Normalized Ratio (INR) blood test measures how fast your blood clots and lets the doctor know if your dose needs to be changed. Testing your blood helps your doctor keep you in a safe range. If there is too much blood thinner in your body, you could bleed too much. If there is not enough, you could get a blood clot.

Regular blood tests are not needed for some of the newer blood thinners.

Too Little Best Range Too much
May cause a blood clot   May cause bleeding


Important reminders:

  • Take your blood thinner as directed by your doctor.
  • Go for blood tests as directed.
  • Never skip a dose.
  • Never take a double dose.

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This booklet is based on a product developed by Carla Huber, A.R.N.P., M.S., Cedar Rapids Community Anticoagulation Clinic, Cedar Rapids, Iowa, under AHRQ Grant No. 1 U18 HSO15830-01 to Kirkwood Community College.

This document is in the public domain and may be used and reprinted without special permission. Citation of the source is appreciated.


How to Order AHRQ Booklets

For more copies of this booklet, E-mail the AHRQ Publications Clearinghouse at or call the toll-free number: 1-800-358-9295.

This booklet and a video on blood thinner pills are available at For other consumer and patient materials, go to the AHRQ Web site at


The name of my blood thinner is: _______________________________


Call your doctor or pharmacy if you have questions about your blood thinner.

  • My doctor's contact information is:
  • My pharmacist's contact information is:












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Page last reviewed September 2015
Internet Citation: Blood Thinner Pills: Your Guide to Using Them Safely. September 2015. Agency for Healthcare Research and Quality, Rockville, MD.