Frequently Asked Questions

The information included on this site is for educational purposes only. It is not intended nor implied to be a substitute for professional medical advice. Readers should consult with their healthcare provider to determine the appropriateness of the information for their own situation or if they have any questions regarding a medical condition or treatment plan.


Missed warfarin doses: “What do I do if I miss a dose of warfarin?”

If you miss your dose of warfarin and realize it before it is time to take your next dose – take it! If it is already time for the next day’s dose, don’t double up and just continue with your usual regimen.

Pain relievers (NSAIDs, APAP): “What over the counter (OTC) medicines can I take for headache or mild pain?”

Tylenol® (acetaminophen/APAP) is OK:
Maximum 2000mg per day while taking warfarin
= 4 extra strength (500mg) tablets
= 6-7 regular strength (325mg) tablets
= 4 Vicodin® (hydrocodone/APAP 5/500) tablets

DON’T use NSAIDs (non-steroidal anti-inflammatory drugs) such as: ibuprofen, naproxen, aspirin (unless prescribed by MD), or aspirin-containing products (like Pepto-Bismol® or Alka Selzer®)

Common drug interactions: “I have started a new medicine, what should I do?”

Many medicines can interact with warfarin and change your dose requirements. Some of the most common interactions:

Can Cause an Increase in INR = Lower Warfarin Dose Requirements:
  • Sulfamethoxazole/Trimethoprim (Septra/Bactrim)
  • Metronidazole (Flagyl)
  • Erythromycin
  • Fluconazole (Diflucan)
  • Amiodarone (Pacerone)

Can Cause a Decrease in INR = Raise Warfarin Dose Requirements:

  • Dicloxacillin (Dynapen)
  • Rifampin
  • Carbamazepine (Tegretol)
  • Phenobarbitol

Can Increase or Decrease INR:

  • Phenytoin (Dilantin)

There are, of course, many more potential interactions… Always call to report newly prescribed medications and supplements to your anticoagulation provider.

Supplement interactions: “I’d like to take an herbal supplement. Will this be a problem with warfarin?”

Many herbal supplements and alternative medicines are not well studied with respect to interactions with prescription medications. Always check with your provider before starting a new non-prescription item.

From the Coumadin package insert:
Caution should be exercised when botanical medicines are taken with warfarin as few studies exist evaluating the potential for interactions.

  • Bromelains, danshen, dong quai, garlic, ginkgo and ginseng are often associated with an increase in the effects of warfarin
  • CoQ10 and St John’s wort are often associated with a decrease in the effects of warfarin
  • Fish oil/omega 3 fatty acids and vitamin E have been associated with increased bleeding when combined with warfarin

Cranberry products: “Can I drink cranberry juice and eat cranberries?”

There have been numerous case reports of a potential warfarin-cranberry interaction over the last several years. The problem with case reports is that it is difficult to establish a strong cause-effect relationship. If one digs deeper into the details of the case reports, there are often other explanations for the elevation in INR--lack of dietary vitamin K, illness, etc.

For more information, please see " The absence of an interaction between warfarin and cranberry juice: a randomized, double-blind trial." As the title indicates, the study concluded that there was no pharmacokinetic interaction. Additionally, it discusses the various case reports and other studies that have been conducted. The author is Jack Ansell MD--the nation's leading expert on anticoagulation. The online article can be found at:

As with the Ansell clinical trial, we have not seen this interaction at our Coumadin Clinic. Does that mean it's not possible? Of course not. If there is anything that we've learned, it is that with warfarin, just about anything is possible. An individual can potentially have a genetic variation that makes them more or less sensitive to various foods, drugs, etc.

In general, an interaction between warfarin and cranberry products is NOT expected. What we advise, as with everything, is moderation--have a glass, not a gallon of cranberry juice.

Vitamin K: “What is vitamin K and do I need to change what I eat now that I’m taking warfarin?”

What it is:
  • A vitamin (just like vitamin A, B, C, etc) that is found in all foods and your body even makes some vitamin K on its own. (It is not potassium—this is abbreviated K+).
  • Vitamin K is found in large amounts in green leafy vegetables (such as spinach, broccoli and brussel sprouts) and liver meats.
  • You do not need to change what you eat:  Just be relatively consistent with foods that contain high amounts of Vitamin K.
  • See below for a list of foods that are higher in Vitamin K



Asparagus (M)

Avocado (M)

Broccoli (H)

Brussel Sprouts (H)

Cabbage (H)

Cabbage, Red (M)

Collard Greens (H)

Endiv, raw (H)

Brussel Sprouts (H)

Cabbage (H)

Green Scallion, raw (H)

Kale, raw leaf (H)

Lettuce (H)

Mustard Greens, raw (H)

Parsley (H)

Peas, green, cooked (M)

Spinach, raw leaf (H)

Turnip greens, raw (H)

Watercress, raw (H)


Fats & Dressings

Margarine (M)

Mayonnaise (H)

Canola Oil (H)

Salad Oil (H)

Soybean Oil (H)


Pickle Dill (M)

Ledgend: (H) - High (M) - Medium (L) - Low


Travel: “I have a trip planned. Do I need to do anything differently?”

  1. Prepare for travel ahead of time—make sure you have a sufficient supply of all of your medications for the entire duration of your trip. You can often obtain a “vacation supply” of your medications from the pharmacy.
  2. When you travel across time zones, it is often easier to take your warfarin at the same time in the new time zone as the time you usually take your warfarin at home. For example: don’t try and figure out the time difference between San Diego and Paris. If you usually take your warfarin at 8pm here, take it at 8pm in Paris.

Bleeding: “Is there anything I can do to quickly stop minor nose bleeds and bleeding from cuts and scrapes?”

There is a non-prescription product on the market called "Wound Seal" that is marketed locally at Walgreens. It is a powder that can be applied to almost any wound. It requires blood to work, but all a patient with a cut needs to do is pour a packet of Wound Seal on the entire surface of the bleeding tear, apply pressure for 10 seconds and then leave it alone. This product also comes as a nasal application for nose bleeds!

Find more information here.


Bridging: "What it bridging?”

“Bridging” is a term that refers to stopping your warfarin (usually for a procedure) and using a different medication (often injectable anticoagulants like heparin or Low Molecular Weight Heparin) to protect you until you are able to resume your warfarin. Your doctor will give you specific stop and start dates for the warfarin and injectable medication.

Aspirin and Surgery: “Do I need to stop my aspirin before surgery?”

ALWAYS discuss surgery and procedures with your cardiologist or primary care provider prior to stopping any medicines.

Dentist visits: “What do I need to do for my dentist appointment?”

There is no need to stop your warfarin for routine dental care: cleaning, fillings, caps, crowns, even root canals. If you are scheduled for extractions or oral surgery, your warfarin may need to be stopped ahead of time. Be sure to call your anticoagulation provider to confirm instructions and always make sure your dentist knows that you take warfarin.

Tips to prevent and control minor bleeding after dental work:

  • Hold cold water in your mouth
  • Apply pressure to the area with gauze or a tea bag
  • Use a hemostatic mouthwash (talk to your provider for a prescription)
  • Avoid vigorous swishing with regular mouthwash
  • Avoid hard to chew foods and hot foods/drinks


Pradaxa and Xarelto: “I’ve heard there are new medicines to replace warfarin. What are they?”

Pradaxa (generic name dabigatran) is a new anticoagulant that was approved by the FDA in 2010. It is currently approved for use in patients 65 and older with AF not caused by a heart valve problem. It is dosed 150mg twice daily and does not require INR monitoring. It has no dietary restrictions and fewer drug-drug interactions than warfarin, but is expensive! It must be kept in the original bottle from the pharmacy—you cannot use a pillbox. Click for more information from the manufacturer:

Xarelto (generic name rivaroxaban) is a new anticoagulant that was approved by the FDA in 2011. It is currently approved for patients with AF not caused by a heart valve problem and for blood clot prevention in patients who have just undergone hip or knee surgery. It is dosed 20mg once daily with dinner and does not require INR monitoring. Click for more information from the manufacturer: