Based on NIH | Can warfarin cause dizziness, and when should I seek medical attention for this side effect?

Warfarin and dizziness: what to know
Warfarin can be associated with dizziness, and this symptom matters because it can signal bleeding or other complications that need prompt attention. Official medication guides list “headaches, dizziness, or weakness” among warning signs of possible bleeding while on warfarin. ^[1] If dizziness appears or worsens on warfarin especially with other bleeding signs it should be taken seriously. ^[1]

Why dizziness can happen on warfarin

• Bleeding risk: Warfarin thins the blood to prevent clots, but too much thinning can lead to bleeding. Dizziness may reflect blood loss (for example, from internal or gastrointestinal bleeding), low blood pressure, or anemia, and medication guides flag dizziness as a concerning symptom in this context. ^[2] In severe cases, bleeding inside the skull can present with headache, dizziness, weakness, or neurologic changes and is a medical emergency. ^[3]
• Ear-related bleeding (rare): There are rare reports of inner-ear (labyrinth) hemorrhage on anticoagulation that can cause acute vertigo and hearing changes. ^[4]
• Out-of-range INR: When the INR is too high, the risk of bleeding rises; many people who come to emergency care while on warfarin have INRs outside the target range, and bleeding is more common with high INRs. ^[5]

When to seek urgent or emergency care

Seek emergency care now (call emergency services or go to the ER) if dizziness is accompanied by any of the following:

• Severe headache, new weakness, confusion, trouble speaking, or vision changes (possible intracranial bleeding). ^{[2] [3]}
• Fainting, chest pain, shortness of breath, or rapid heart rate (could reflect significant blood loss or other emergencies). ^{[2] [3]}
• Vomiting blood or material that looks like coffee grounds. ^{[2] [3]}
• Red or black stools (tarry), or coughing up blood. ^{[2] [3]}
• Pink, red, or brown urine. ^{[1] [2]}
• Unusual bruising, nosebleeds, or bleeding gums that are heavy or do not stop, or bleeding from cuts that takes a long time to stop. ^{[1] [2]}
• Menstrual or vaginal bleeding that is heavier than normal. ^{[1] [2]}

Seek prompt same‑day medical advice (contact your clinician or anticoagulation clinic) if:

• You have new or persistent dizziness without the severe signs above, especially if you recently changed your warfarin dose, started/stopped another medication, or changed your diet. ^{[1] [2]}
• You notice milder bleeding such as brief nose or gum bleeding, or unusual bruising, even if it stops quickly, since it may indicate your INR is drifting high. ^{[6] [7]}

What to do while you seek care

• Do not take extra warfarin doses; take only as prescribed and do not skip doses unless a clinician tells you to. ^[1]
• Avoid new over‑the‑counter pain relievers like ibuprofen or aspirin unless your clinician said they are safe, since they can increase bleeding risk. ^[7]
• If you have any bleeding sign with dizziness, arrange urgent INR testing and medical review. ^[5]
• If you had a fall or head injury even if you feel okay get checked urgently because anticoagulation raises the risk of delayed internal bleeding. ^{[2] [3]}

Common triggers that can raise bleeding risk (and dizziness)

• Drug interactions (antibiotics, antifungals, amiodarone, many others) can raise INR and bleeding risk. ^[7]
• Alcohol binges and sudden diet changes (especially vitamin K intake) can push INR out of range. ^[7]
• Illnesses (fever, diarrhea), poor oral intake, or dehydration may alter warfarin effect and contribute to dizziness. ^[7]

How your care team will evaluate dizziness on warfarin

• History and exam to look for bleeding, neurologic signs, or ear symptoms. ^{[2] [3]}
• INR test to check how thin your blood is; values above the target increase bleeding risk and guide whether reversal is needed. ^[5]
• Blood counts (hemoglobin/hematocrit) to look for anemia from occult bleeding. ^[7]
• Imaging if indicated (for example, head CT for severe headache/neurologic signs; targeted imaging if gastrointestinal bleeding is suspected). ^{[8] [9]}
• If dangerous bleeding is confirmed or strongly suspected, clinicians may reverse warfarin with vitamin K and clotting factor concentrates while treating the bleeding source. ^{[8] [9]}

Quick reference: red‑flag symptoms

• Headache plus dizziness/weakness or neurologic changes → ER now. ^{[2] [3]}
• Vomiting blood, black or bloody stools, coughing up blood → ER now. ^{[2] [3]}
• Heavy or persistent bleeding/bruising, pink/red/brown urine → Urgent care/ER. ^{[1] [2]}
• New or persistent dizziness without red flags → Call your clinician the same day for advice and INR check. ^{[6] [5]}

---

Key takeaways

• Yes, warfarin can be linked with dizziness, and it is treated as a potential warning sign of bleeding. ^[1]
• Combine dizziness with any bleeding sign or severe headache/neurologic symptoms, and you should seek emergency care. ^{[2] [3]}
• If dizziness is mild and isolated, contact your care team promptly for guidance and an INR check, because out‑of‑range anticoagulation is common and manageable. ^{[5] [6]}