Warfarin what you need to know?

Warfarin drug is a medicine that helps to prevent blood clots. There are two available brand name of warfarin, (Coumadin & Jantoven).

Why do you need warfarin?

You need warfarin because you have, or are at risk of having a blood clot. Clots are harmful; they can block the blood flow in an artery or vein.

Dosage time table:

Take your tablets (as one dose), once a day, at the same time each day. Evening is best so you can have your blood test in the morning.

If you forget the dose what you need to do?

If it is the same day, take the missed dose as soon as you remember. If you forgot yesterday’s dose only take the dose you are meant to have today. NEVER take a catch-up dose and never take more than one dose a day.

How long do you need to take warfarin?

It depends on your condition. Your doctor will tell you how long you need to take it.

During Pregnancy:

Warfarin should not be used during pregnancy as it can harm your baby. Talk to your doctor if you take warfarin and think you might be pregnant, or want to have a baby.

Breast feeding:

Warfarin is safe during breast feeding; it does not pass into the breast milk.

Your diet:

Eat a balanced low-fat diet. Some foods have vitamin K in them which can affect how warfarin works (eg spinach, broccoli, lettuce, soya beans, beef, liver, alfalfa and green tea). Eat only small amounts of these. More than two standard alcoholic drinks per day can increase the risk of bleeding. Do not have any more than this.

Required Lab Tests:

Everyone’s dose is different, and your dose has to be right for you. To find the right dose you need to have a blood test regularly called the INR (International Normalised Ratio). The INR measures how fast your blood clots and should be between 2 and 4. The test is usually done at a laboratory but some pharmacies can do it for you.

Doctor Suggestions:

Your doctor will tell you about the following:
• The INR level that is best for you
• The warfarin dose you need to take
• How often you need an INR blood test
If you are in hospital, your blood will be tested there. When you are at home your doctor will give you a form to take to a laboratory when you need a blood test.

Warfarin Dosage Guide:

Initially, 2–5 mg/ daily for 2 days OR 5–10 mg daily for 1–2 days, adjusting the dose based on INR results. Usual maintenance dose: 2–10 mg/day, but may vary outside these guidelines.

For Children:
Initially, 0.05–0.2 mg/kg/day. Maximum: 10 mg. Maintenance: Adjust based on INR.



Cross-check dose with coworker. Determine INR before administration and daily following therapy initiation. When stabilized, follow with INR determination q4–6wks. Obtain genotyping prior to initiating therapy if available.


Monitor INR reports diligently. Assess Hct, platelet count, ALT, AST, urine/stool for occult blood. Be alert to complaints of abdominal/back pain, severe headache (may be sign of hemorrhage). Decrease in B/P, increase in pulse rate may be sign of hemorrhage. Question for increase in amount of menstrual discharge. Assess peripheral pulses; skin for ecchymoses, petechiae. Check for excessive bleeding from minor cuts, scratches. Assess gums for erythema, gingival bleeding.


Occasional: GI distress (nausea, anorexia, abdominal cramps, diarrhea).
• Rare: Hypersensitivity reaction (dermatitis, urticaria), esp. in those sensitive to aspirin.

FDA Disclaimer
The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.

Leave a Reply