💊 Warfarin – Information for Older Adults
Plain-language information about warfarin in older adults. This page is for older Canadians and their caregivers. It does not replace advice from your own health-care provider.
⚠️ High-Alert Medication
Warfarin is a high-alert medication – it's very effective but requires careful monitoring. Too much can cause dangerous bleeding; too little may not protect you from clots. Regular blood tests and close communication with your health-care team are essential.
Warfarin
Anticoagulant ("Blood Thinner")
1. What is warfarin used for?
Warfarin is an anticoagulant, commonly called a "blood thinner." It helps prevent harmful blood clots from forming or growing. Warfarin has been used safely for over 60 years.
Warfarin is commonly used for:
- Atrial fibrillation (AFib) – to reduce the risk of stroke
- Deep vein thrombosis (DVT) – blood clots in the legs
- Pulmonary embolism (PE) – blood clots in the lungs
- Mechanical heart valves – to prevent clots from forming on artificial valves
- After certain surgeries – to prevent clots during recovery
- Some clotting disorders
💡 Why blood clots are dangerous
Blood clots can block blood flow to vital organs. A clot traveling to the brain causes a stroke. A clot in the heart's arteries causes a heart attack. A clot in the lungs causes a pulmonary embolism. Warfarin helps protect you from these serious events.
2. How does warfarin usually help?
Warfarin works by interfering with vitamin K, which your body needs to make clotting factors:
Reduces the blood's ability to form clots
Helps stop existing clots from getting bigger
In AFib, significantly lowers the chance of stroke
Protects against clots in legs and lungs
💡 Important to understand
Warfarin does not dissolve existing clots – your body does that over time. Warfarin prevents clots from growing and new clots from forming while your body heals.
3. Understanding INR testing
Unlike most medications, warfarin requires regular blood tests to make sure the dose is right. This test is called the INR (International Normalized Ratio).
🩸 What is INR?
INR measures how long it takes your blood to clot. A higher INR means your blood clots more slowly. For most people on warfarin, the goal is to keep INR in a target range.
*Most common target. Some conditions (like mechanical heart valves) may need a different range. Ask your provider what YOUR target is.
👨⚕️ About INR testing:
📝 Keep records
Write down your INR results and doses. Bring this record to all medical appointments. This helps any provider who sees you understand your warfarin history.
4. How warfarin is usually taken
⚠️ Critical: Follow your specific instructions
Never change your warfarin dose on your own. Only change the dose when your warfarin clinic or provider tells you to. Even small changes can affect your INR significantly.
Usually taken once a day
Pick a consistent time – many people take it in the evening
Can be taken either way – just be consistent
Warfarin tablets come in different colors for different strengths – know your color
🎨 Warfarin tablet colors (in Canada)
Each strength is a different color to help prevent mistakes:
- 1 mg – Pink
- 2 mg – Lavender/Purple
- 2.5 mg – Green
- 3 mg – Tan/Beige
- 4 mg – Blue
- 5 mg – Peach
- 6 mg – Teal/Blue-green
- 7.5 mg – Yellow
- 10 mg – White
If your tablets look different than expected, check with your pharmacist before taking them.
❓ If you miss a dose
Take it as soon as you remember on the same day. If you don't remember until the next day, skip the missed dose – don't double up. Write down that you missed a dose and tell your warfarin clinic at your next test.
⚠️ If you accidentally take too much
Contact your warfarin clinic or provider right away. They may want to check your INR sooner or adjust your next doses. Don't panic, but do get guidance.
5. Bleeding risks and warning signs
The main risk of warfarin is bleeding. Because your blood doesn't clot as easily, cuts take longer to stop, and you may bruise more easily. Some bleeding signs are minor, but others need immediate attention.
🟡 Minor bleeding (common)
May not require emergency care, but mention to your clinic:
- Easy bruising or small bruises
- Minor bleeding from small cuts (taking longer to stop)
- Occasional nosebleeds that stop with pressure
- Minor bleeding when brushing teeth
🟠 Serious bleeding (call your clinic promptly)
Contact your warfarin clinic or provider soon:
- Frequent nosebleeds or ones hard to stop
- Heavy bleeding from gums
- Blood in urine (pink, red, or brown)
- Heavier than normal menstrual bleeding
- Unusual or excessive bruising
- Red or dark brown vomit
🔴 Emergency bleeding (call 911)
Seek immediate help:
- Black, tarry stools or bright red blood in stool
- Vomiting blood or material like coffee grounds
- Severe headache unlike any before
- Sudden confusion, weakness, or trouble speaking (stroke signs)
- Heavy bleeding that won't stop
- Any head injury or serious fall
🚨 Head injuries are always serious on warfarin
If you fall and hit your head, or have any head injury, seek medical attention right away – even if you feel fine. Bleeding inside the head may not cause symptoms immediately but can become life-threatening. Don't "wait and see."
6. Food, vitamin K, and diet
Warfarin works by blocking vitamin K. Foods high in vitamin K can reduce warfarin's effect, making your blood clot more easily. The key is consistency – not avoidance.
💡 The goal: Be consistent, not restrictive
You don't need to avoid vitamin K foods entirely – they're healthy! Instead, try to eat similar amounts week to week. Big changes in vitamin K intake can make your INR fluctuate and harder to control.
🥬 Foods HIGH in Vitamin K
Be consistent with these (don't suddenly eat much more or much less):
🍷 Alcohol and warfarin
Small, consistent amounts of alcohol (like one drink) are usually okay, but check with your provider. Avoid binge drinking – drinking a lot at once can significantly affect your INR and increase bleeding risk. Also, alcohol increases fall risk, which is dangerous when on warfarin.
🍊 Other foods to know about
- Cranberry juice/products – may increase warfarin's effect; use consistently or avoid large amounts
- Grapefruit – can interact with some medications; ask your provider
- Mango – in large amounts, may affect INR
7. Drug and supplement interactions
Warfarin interacts with many medications and supplements – more than almost any other drug. Some increase warfarin's effect (higher bleeding risk), others decrease it (higher clot risk).
⚠️ Golden Rule
Always tell your warfarin clinic or pharmacist before starting, stopping, or changing ANY medication – including over-the-counter drugs, vitamins, and herbal products. Never assume something is safe just because it's "natural" or available without a prescription.
⬆️ May INCREASE bleeding risk
- ASA/Aspirin (even low-dose)
- Ibuprofen, naproxen (NSAIDs)
- Some antibiotics
- Acetaminophen (high doses)
- Fish oil (high doses)
- Vitamin E (high doses)
- Ginkgo, garlic, ginger supplements
- Some antidepressants
⬇️ May DECREASE warfarin's effect
- Vitamin K supplements
- Some seizure medications
- Rifampin (antibiotic)
- St. John's Wort
- Coenzyme Q10
- Ginseng
- Green tea extract (large amounts)
💊 Pain relief while on warfarin
Safest choice: Acetaminophen (Tylenol) in recommended doses
Use with caution: NSAIDs (Advil, Aleve) – increase bleeding risk significantly
Ask first: Always check with your provider or pharmacist before taking any pain medicine
8. Safety tips and lifestyle
Carry a card or wear a bracelet saying you take warfarin – critical in emergencies
Regular testing is essential for safe warfarin use
Dentists, surgeons, anyone – they need to know before any procedure
Reduces risk of cuts while shaving
Be gentle on gums to reduce bleeding
Remove trip hazards, use good lighting, hold railings
Protect yourself from cuts and scrapes
Contact sports or activities with high injury risk need discussion with your provider
✈️ Traveling with warfarin
- Bring enough medication for your trip plus extra
- Carry medications in your carry-on bag
- Bring a list of your medications and your target INR
- Know where you could get INR tested if needed
- Be consistent with diet even while traveling
- Wear your medical ID
9. When to call your warfarin clinic, doctor, or pharmacist
(Non-urgent)
Contact your health-care provider or warfarin clinic if:
- You miss a dose or accidentally take an extra dose
- You notice more bruising or minor bleeding than usual
- You start or stop ANY medication, vitamin, or supplement
- Your diet has changed significantly
- Your alcohol intake has changed
- You're planning surgery, dental work, or any medical procedure
- You become pregnant or are planning pregnancy
- You have diarrhea, vomiting, or illness lasting more than a day
- You're having trouble taking warfarin as prescribed
- Your pharmacy gave you tablets that look different than usual
10. When to call 911 or go to the emergency department
🚨 Call 911 immediately if:
- Any head injury or serious fall – even if you feel okay
- Black, tarry stools or bright red blood in stool
- Vomiting blood or material that looks like coffee grounds
- Heavy bleeding that won't stop with pressure
- Severe headache – the worst headache of your life
- Sudden confusion, trouble speaking, or weakness – could be stroke
- Sudden vision changes
- Coughing up blood
- Blood in urine that is heavy or with clots
- Severe abdominal pain
If possible, do not drive yourself. Ask someone to call for you or call an ambulance.
Tell emergency responders you take warfarin.
🧠 Remember "FAST" for stroke signs
Face drooping • Arm weakness • Speech difficulty • Time to call 911
Warfarin helps prevent strokes, but if stroke signs appear, every minute counts.
11. Questions to ask your doctor or warfarin clinic
You can print these questions and bring them to your next appointment:
⚠️ Important Disclaimer
The information on SeniorHealthGuide.ca is general and may not fit your exact situation. It is for education only.
It does not replace medical advice, diagnosis, or treatment. Only a health professional who knows your medical history can tell you what is right for you.
Never start, stop, or change any medication, or make major changes to your diet or alcohol use, without checking with your doctor, warfarin clinic, or pharmacist.