Warfarin Dosages: Your GoodRx Guide

If you or a loved one have ever experienced a blood clot, there’s a good chance you’ve heard of warfarin (Coumadin, Jantoven). Warfarin is an anticoagulant (blood thinner) medication that has been used for decades to treat and prevent blood clots.

One unique feature of warfarin is that it requires regular blood testing to ensure you’re taking a safe and appropriate dosage. Warfarin can cause serious bleeding if there is too much in your body, and there’s a risk of clotting if there isn’t enough.

In this guide, we’ll review typical warfarin dosages. Since this medication needs to be monitored for safety purposes, you should take your dose exactly as prescribed. If you have any questions about your warfarin dosage, speak to your healthcare provider or pharmacist.

Promotion disclosure

Warfarin

Avg retail price

$4.00(Save Free%)

GoodRx discount

$4.00

See all discounts

How it works

Use GoodRx to find medications, pharmacies, and discounts.

GoodRx discounts can help you pay less for your prescription.

Bring your free coupon or savings card to the pharmacy.

What’s the typical warfarin dosage for adults?

Your warfarin dose is individualized based on what you’re treating and how you respond to the medication. The typical starting dose of warfarin in adults is 2 mg to 5 mg by mouth once daily. Depending on your international normalized ratio (INR) results, the typical maintenance dose ranges from 2 mg to 10 mg once daily. Your INR is a blood test that tells your healthcare provider how quickly your blood can clot, which helps them determine the right warfarin dosage for you.

To make sure that your warfarin treatment is effective, each health condition that it’s used to treat has a “goal” INR. Your healthcare provider will perform routine follow-up tests and warfarin dosage adjustments to keep your INR within range.

The conditions warfarin can treat are discussed in the table below.

The warfarin dose that will keep you within your INR goal will look different for each person. It will depend on your genetics, other medications, and even diet. This is why warfarin comes in many different doses for you and your healthcare provider to choose from. It’s available in nine different tablet doses:

• 1 mg

• 2 mg

• 2.5 mg

• 3 mg

• 4 mg

• 5 mg

• 6 mg

• 7.5 mg

• 10 mg

What’s the typical warfarin dosage for children?

There are no anticoagulant drugs approved for children. If your child needs to treat a blood clot, their healthcare provider will help you make the safest choice for using an anticoagulant off-label. Despite the relative lack of data, warfarin is the most common blood thinner used for children. 

Warfarin dosing in children is based on body weight, and the INR goals are usually similar to adults. However, warfarin dosing in children can be challenging. The safety and effectiveness of warfarin in children is unpredictable because their bodies are constantly changing. If warfarin use is necessary in a child, more frequent INR monitoring is recommended for safety purposes.

Are there any dosage adjustments for medical conditions?

Yes. Different health conditions and lifestyles can affect your warfarin dosage. Your healthcare provider will consider several factors when starting or adjusting your dose.

Diet

Warfarin works by preventing a nutrient called vitamin K from making blood clotting proteins. Your diet is the most common source of vitamin K. The more vitamin K you ingest, the less effective warfarin becomes.

Leafy, green vegetables contain the highest amounts of vitamin K. Other foods also contain it. If you eat lots of foods that are high in vitamin K, your healthcare provider may need to give you a higher dose of warfarin.

You don’t need to make any big changes to your diet if you’re new to taking warfarin. The important thing is to keep a consistent diet. If you suddenly stop eating foods that are high in vitamin K, you’re likely to experience more warfarin side effects. Be sure to report any meaningful changes in your diet to your provider so they can adjust your dosage accordingly.

Age

Older adults are at higher risk of experiencing bleeding problems compared to younger adults. A lower starting warfarin dose is recommended in older adults, but the specific dosage varies by person.

Genetics

Some people have genetics that interfere with how their liver breaks down warfarin. Since this can make warfarin too abundant in your body, you may be started on a lower dose. Your healthcare provider may run genetic tests to see if this applies to you.

Liver problems

As mentioned, warfarin is broken down by your liver. Having liver issues may prevent your body from breaking down warfarin efficiently. Your provider may recommend a lower starting dose to prevent accidental bleeding or other possible warfarin side effects.

Interactions

Warfarin has many drug interactions. In most cases, these interactions cause higher amounts of warfarin in your body. This can increase your bleeding risk. 

Some of the most common warfarin interactions include:

• Blood thinners like apixaban (Eliquis), rivaroxaban (Xarelto), and clopidogrel (Plavix)

• Antibiotics like ciprofloxacin (Cipro), metronidazole (Flagyl), and clarithromycin

• Antifungals like fluconazole (Diflucan) and ketoconazole

• Herbal products like St. John’s wort and Ginkgo biloba

There may still be an interaction even if the medication you take isn't on this list. Make sure to keep an updated list of all your medications including over-the-counter and herbal products. Your healthcare provider or pharmacist can check this list for potential interactions with warfarin.

What happens if you miss a dose of warfarin?

If you miss a dose of warfarin, take it as soon as you remember. If it is getting close to your next dose, skip the missed dose and take the next scheduled dose at your regular time. To avoid side effects, be sure not to double up on your warfarin dose to make up for a missed dose.

Since a missed dose can affect your INR, be sure to let your healthcare provider or pharmacist know as soon as possible. This may affect any dosage adjustments at your next clinic visit.

What should you do if you take too much warfarin?

Warfarin can cause serious bleeding if you take too much. In fact, warfarin has a boxed warning about its bleeding risk. This is the most serious type of FDA warning about a medication. This is why it’s important to take your warfarin dosage exactly as prescribed by your provider.

Common signs of bleeding include:

• Bleeding from the gums

• Blood in urine

• Blood in stool, or black tarry stool

• Excessive menstrual bleeding

• Nosebleeds

• Unexplained bruising under the skin

• Vomiting blood 

If you or a loved one have taken too much warfarin, call your healthcare provider right away. You could also contact Poison Control at 1-800-222-1222 as an alternative. They can help guide you through the situation at hand. But if you’re experiencing severe side effects, go to the nearest emergency room. 

It’s not recommended to try fixing your INR by yourself with diet changes. It’s better to talk to a medical professional as soon as possible.

How to save on warfarin

There are many ways to save on warfarin, which is available as both a brand-name and generic medication. GoodRx can help you save over 65% off the average retail price of the generic version. Generic warfarin’s price at certain pharmacies is as low as $4.00 with a free GoodRx discount.

Why trust our experts?

Written by:

Sheila McAdoo, PharmD

Sheila McAdoo, PharmD, is a licensed pharmacist in Virginia, New York, and the District of Columbia. She has worked in the pharmacy industry for 12 years and currently works as a community pharmacist.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Tegan Smedley, PharmD, APh

Tegan Smedley, PharmD, APh, has 10 years of experience as a pharmacist. She has worked in a variety of settings, including retail, hospital, and ambulatory care.

Our editorial standards

Meet our experts