What to Know When Taking Warfarin

Before you start warfarin

Before starting warfarin, tell your health care provider if you have ever had:

• A stomach ulcer.

• Vomiting of blood, or red or black stools.

• Any heart or blood vessel disease.

• A blood disorder.

• A stroke or transient ischemic attack (TIA).

• Kidney or liver disease.

• Lupus or another collagen-vascular disease.

Also tell your provider if you:

• Are pregnant or breastfeeding.

• Are younger than 18.

• Had a recent dental procedure or surgery.

• Have an upcoming dental procedure or surgery.

• Had a spinal puncture, recent spinal anesthesia, or spinal surgery.

Many medicines cause problems if you take them while you’re on warfarin. Tell your health care provider about every medicine you take. It may be dangerous for you to take some medicines and supplements, such as:

• Medicines that thin your blood, such as aspirin, clopidogrel, ticagrelor, or prasugrel.

• Antibiotics.

• Heart medicines.

• Cimetidine.

• Ibuprofen.

• Naproxen, ketoprofen, or other arthritis medicines.

• Medicines for depression, cancer, HIV, diabetes, seizures, gout, high cholesterol, or thyroid.

• Vitamins that have vitamin K.

• Herbal products like ginkgo, CoQ10, garlic, or Saint John's wort.

This list does not include all medicines and supplements that can affect how your medicine works. Talk with your health care provider and pharmacist. Your provider may change or tell you to stop taking some of these before you take warfarin.

Taking your warfarin as directed

You’ll need to take the medicine exactly as directed by your health care provider. Make sure to:

• Take it at the same time each day.

• Take it with a full glass of water. You can take it with or without food.

• Use a pillbox to help keep track of your doses.

• Call your provider right away if you miss a dose. They can tell you how much to take.

• Never take a double dose. If you take too much, it can cause bleeding on the outside and inside of your body.

Keeping certain foods steady in your diet

Some foods can affect how warfarin works.

Many foods contain vitamin K. Vitamin K is a substance that helps your blood clot. So eating foods that contain vitamin K can affect the way warfarin works. You don’t need to avoid foods that have vitamin K. But you do need to keep the amount of them you eat steady—about the same day to day. Foods that have vitamin K include:

• Asparagus.

• Avocado.

• Broccoli.

• Cabbage.

• Kale.

• Oils such as soybean, canola, and olive.

• Spinach and some other leafy green vegetables.

Other foods and drinks can affect the way your blood clots. You’ll also need to keep the amounts of these steady in your diet. These include:

• Cranberries and cranberry juice.

• Fish oil supplements.

• Garlic, ginger, licorice, and turmeric.

• Herbs used in herbal teas or supplements.

• Alcohol.

If you change your diet for any reason, such as in the case of illness or to lose weight, tell your health care provider.

Preventing injury

When you’re on warfarin, you’ll need to be extra careful. Because it makes you bleed more, you’ll need to protect yourself from breaks in the skin. To do this:

• Don’t go barefoot. Always wear shoes.

• Don’t trim corns or calluses yourself.

• Use an electric razor instead of a manual one.

• Use a soft-bristled toothbrush and waxed dental floss.

You’ll also need to avoid any activities that may cause injury. If you fall or are injured, call your health care provider right away. You could be bleeding inside your body and not know it. Make sure to get medical attention right away if you have:

• A serious fall.

• A blow to the head.

• Any other kind of injury.

Getting your blood tested

You’ll need to have your blood tested on a regular schedule. Your health care provider will tell you how often you need to have your blood tested. This is to make sure you’re taking the right amount of warfarin. Too much can cause excess bleeding, which can be very serious. Too little may not prevent blood clots from harming you.

The blood tests check your international normalized ratio (INR) and prothrombin time (PT). These show how quickly your blood clots. Together the test is called PT/INR.

You may need to visit a hospital or clinic to have your blood tested. Or a nurse may come to your home and test your blood. In some cases, you may be able to test your blood at home with a small machine. Talk with your provider to find out what’s best for you. Do not miss any appointments to get your blood tested. If you have a blood test outside of your provider’s office, make sure to call them as soon as you get your test results.

After the blood test, your provider may tell you to change your dose of warfarin. Take the medicine exactly as directed. Don’t stop taking it unless your provider tells you to.

Important tips

While on warfarin:

• Make sure you report any new medicines started by any of your providers to the team that manages your warfarin. You may need to be monitored more often after you start a new medicine, change the dose, or stop a medicine you have been on.

• Don't stop taking the medicine without talking with your provider. If you have an upcoming surgery or procedure, your surgeon and your health care provider will give you specific instructions on how to change your dose to prevent excessive bleeding for your procedure or surgery.

• Tell all of your health care providers that you take warfarin. This includes your dentist, chiropractor, nurses, physical therapist, and home health nurse.

• Wear a medical alert bracelet or carry an ID card in your wallet that says you take warfarin.

• Keep all appointments for your blood tests.

• Talk with your provider before taking any new medicine. This includes any over-the-counter medicines. It also includes supplements, herbs, or vitamins.

• Tell the provider who manages your warfarin if you change your contact information.

Call 911

Warfarin increases your risk of bleeding. Call 911 and your health care provider right away before you take your next dose of warfarin if you have:

• Bleeding that doesn’t stop.

• Coughed up blood.

• Vomited blood or what looks like coffee grounds.

• Nausea, bloating, or diarrhea.

• Dark red or brown urine.

• Red or black, tarry stools.

• Dizziness, headache, confusion, weakness, or fatigue.

• Chest pain or trouble breathing.

• A serious fall or a blow to the head.

• Signs or symptoms of a stroke (facial drooping, trouble speaking, weakness on one side of the body).

• Signs of an allergic reaction such as swelling of the mouth, lips, throat, tongue, or face. Signs can also include a rash, hoarseness, and trouble breathing or speaking.

• Severe pain, loss of sensation, color change to the skin, and temperature change to a part of the skin or an extremity such as the arm or leg. This may be a sign of a rare but serious side effect of warfarin in which the skin and tissue do not get blood flow.

When to get medical care

Other urgent or important signs and symptoms that you should call your provider about include:

• Swelling or pain after an injury.

• Swelling or pain at an injection site.

• Bleeding gums after brushing your teeth.

• A fever or an illness that gets worse.

• Bleeding hemorrhoids.

• A heavier-than-normal period or bleeding between periods.

• Red or black-and-blue marks (bruises) on the skin that get larger.

[NOTE: This information topic may not include all directions, precautions, medical conditions, medicine/food interactions, and warnings for this medicine. Check with your health care provider, nurse, or pharmacist for any questions that you may have.]