Conditions › Blood & cancer
Warfarin Nursing Considerations
Warfarin nursing considerations: follow the INR (the goal is usually 2 to 3 for most indications), watch for bleeding and check every new drug for interactions. Vitamin K reverses warfarin; teach the client to keep vitamin K foods steady, report bleeding and avoid warfarin in pregnancy.
How it works
Warfarin: vitamin K antagonist
No class ending to learn. It blocks vitamin K from building clotting factors II, VII, IX and X. Taken by mouth once daily. 1,2
More vitamin K in the diet works against warfarin. That one fact explains the food teaching.
Slow on, slow off
Some effect within 24 hours, but full effect takes 5 to 7 days. It lingers 5 or more days after the last dose. 3,2
Old clotting factors must wear out first. That is why heparin or enoxaparin overlaps at the start.
Check before you give it
INR: the warfarin lab
Normal INR is about 1 (labs vary). Goal is usually 2 to 3; some clients with mechanical heart valves aim for 2.5 to 3.5. 3
Higher INR means thinner blood and more bleeding risk. Always check the goal in the order.
INR below goal: clot risk
Blood is too thick for the condition. Ask about missed doses, more vitamin K foods or new drugs, and report to the provider. 2,3
A new daily kale smoothie can pull the INR below goal.
INR above goal: bleeding risk
Bleeding risk rises above an INR of 4. Assess for bleeding, hold the dose per orders and report. The provider may order vitamin K. 2
A high INR with no bleeding may only need held doses. Active bleeding is an emergency.
Side effects and toxicity to watch
Many drug interactions
Antibiotics, antifungals, amiodarone, herbals, aspirin and NSAIDs can shift the INR or add bleeding. Check INR more often with any change. 2,3
A short antibiotic from urgent care can push the INR up. Tell every prescriber about warfarin.
Bleeding: what to report
Black or bloody stools, red or pink urine, bleeding gums, nosebleeds, coffee-ground vomit, a sudden severe headache. 3,2
A small bruise is expected on warfarin. Black, tarry stool is not: call.
Vitamin K reverses warfarin
Phytonadione by mouth or IV. IV acts faster (about 1 to 2 hours vs 6 to 10 by mouth) and is used for serious bleeding. 3
Write out "vitamin K": K alone can be misread as potassium.
Pregnancy: avoid warfarin
Causes birth defects and fetal bleeding: not used in pregnancy except some clients with mechanical valves. Teach effective contraception. 2
A client on warfarin who may be pregnant needs the provider told right away.
Rare: skin necrosis, purple toes
Skin or tissue can die in the first few days of therapy. Purple or dark painful toes can signal tiny cholesterol emboli. 2
Report new pain, color or temperature change in any area right away.
Client teaching
Vitamin K foods: keep them steady
Do not avoid greens. Eat about the same amount each week. A sudden increase lowers the INR; a sudden stop raises it. 3
Kale, spinach, broccoli and collards are high in vitamin K. Steady intake, not zero.
Teach: warfarin safety
Same time daily, keep every INR check, wear a medical alert ID, soft toothbrush, electric razor, avoid alcohol. 3
Bring the warfarin list to every visit, including the dentist.
NCLEX traps
Heparin vs warfarin
Heparin: IV or subcut, works at once, aPTT, antidote protamine. Warfarin: by mouth, takes days, INR, antidote vitamin K. 3
They overlap at the start: heparin or enoxaparin keeps going until the INR reaches goal.
Try a warfarin question
NCLEX-style, approved by a licensed RN. Pick an answer, check it, then read the rationale.
Question 1 · Pharmacological and Parenteral Therapies
A client taking warfarin for atrial fibrillation has an INR of 4.8. Which nursing action is the priority?
Show answer and rationale
Answer: B. The therapeutic INR goal for warfarin is 2.0-3.0 (or 2.5-3.5 for a mechanical valve), so an INR of 4.8 is well above therapeutic and places the client at high risk for bleeding, requiring the nurse to hold the dose and notify the provider. Administering the scheduled dose would further increase an already dangerous INR. Increasing the dose would worsen the bleeding risk and is never appropriate with a supratherapeutic level. Simply documenting without acting fails to address a safety concern.
Checked against: OpenStax Pharmacology for Nurses, 20.2
Keep studying warfarin in NurseLingo Pro
Pro has 40 warfarin questions like these, with a rationale for every answer. Everything for warfarin in one place. A free account gets 5 free opens of any condition; Pro opens all 277.
Test yourself: free pharmacology practice questions with answers and rationales.
Frequently asked questions
What should the nurse check before giving warfarin?
INR: the warfarin lab: Normal INR is about 1 (labs vary). Goal is usually 2 to 3; some clients with mechanical heart valves aim for 2.5 to 3.5. INR below goal: clot risk: Blood is too thick for the condition. Ask about missed doses, more vitamin K foods or new drugs, and report to the provider. INR above goal: bleeding risk: Bleeding risk rises above an INR of 4. Assess for bleeding, hold the dose per orders and report. The provider may order vitamin K.
What are the nursing considerations for warfarin?
Warfarin nursing considerations: follow the INR (the goal is usually 2 to 3 for most indications), watch for bleeding and check every new drug for interactions. Vitamin K reverses warfarin; teach the client to keep vitamin K foods steady, report bleeding and avoid warfarin in pregnancy.
What should you monitor with warfarin?
Monitor the INR (usually a goal of 2 to 3) and watch for bleeding: gums, nosebleeds, blood in urine or stool, and easy bruising. Check every new medication for interactions and teach the client to keep vitamin K foods steady. Vitamin K reverses warfarin.
What is the most common side effect of warfarin?
Bleeding. It can be minor (bruising, bleeding gums, nosebleeds) or serious (blood in urine or stool, vomiting blood, a severe headache). Clients should report bleeding and keep their INR checks.
Related cheat sheets
Sources
For study only, not medical advice. Follow your program, your facility's policies and the provider's orders.