Can Warfarin Cause Dizziness? Understanding the Side Effects

October 12, 2025 •

4 min read

Warfarin is one of the top drugs associated with emergency room visits for adverse events in older adults [1.9.3]. Dizziness is listed as a potential side effect, and understanding its context is crucial for safety. So, can warfarin cause dizziness? Yes, it can, both directly and as a symptom of a more serious complication like internal bleeding [1.2.1, 1.2.5].

Quick Summary

Warfarin, a common anticoagulant, lists dizziness as a potential side effect. This symptom can occur on its own or, more critically, as a sign of excessive bleeding. Patients should monitor for dizziness and report it to their healthcare provider.

Key Points

Direct Side Effect: Dizziness is a listed less common or rare side effect of warfarin, sometimes occurring when changing positions suddenly [1.2.1, 1.3.1].
Warning Sign for Bleeding: More importantly, dizziness, weakness, or a severe headache can be a symptom of serious internal bleeding, a major risk of warfarin [1.2.5, 1.2.6].
INR Monitoring is Crucial: Regular blood tests (INR) are required to ensure warfarin's dosage is safe and effective, as levels outside the therapeutic range increase risks [1.2.2].
Numerous Interactions: Warfarin interacts with many foods (especially those high in Vitamin K), other medications (like ibuprofen), and herbal supplements, which can alter its effectiveness [1.7.1].
Seek Immediate Help: Dizziness combined with symptoms like a severe headache, black stools, or unusual bruising requires immediate medical attention [1.4.5].
Alternatives Exist: Newer drugs called DOACs (e.g., Eliquis, Xarelto) are available and have a lower risk of certain types of bleeding and require less monitoring than warfarin [1.6.1, 1.8.1].

What is Warfarin and How Does It Work?

Warfarin is an oral anticoagulant, commonly known as a blood thinner, prescribed to prevent and treat blood clots [1.5.1]. It is used for conditions such as atrial fibrillation (AFib), deep vein thrombosis (DVT), pulmonary embolism (PE), and after heart valve replacement. Its primary function is to inhibit the body's ability to form blood clots by blocking the action of vitamin K, a crucial nutrient in the blood clotting process [1.5.5, 1.7.1]. Because its effect can be powerful, patients on warfarin require regular blood tests, known as International Normalized Ratio (INR) tests, to ensure their blood is within a specific therapeutic range—not too thin to cause bleeding, and not too thick to allow clots [1.2.2].

Can Warfarin Directly Cause Dizziness?

Dizziness is listed as a less common or rare side effect of warfarin [1.2.1, 1.2.4]. Some patients may experience dizziness, faintness, or lightheadedness, particularly when getting up suddenly from a lying or sitting position [1.3.1]. While the direct mechanism for this is not always clear, it can be a primary side effect for some individuals [1.3.2]. However, the presence of dizziness while taking warfarin should always be taken seriously, as it can also be an indicator of a more dangerous underlying issue.

Dizziness as a Symptom of a More Serious Problem

The most significant risk associated with warfarin is bleeding [1.2.5]. Dizziness, especially when sudden, severe, or accompanied by weakness, can be a sign of internal bleeding [1.2.6, 1.4.5]. An overdose or a high INR level significantly increases this risk. Bleeding in the brain (intracranial hemorrhage) can manifest as a sudden, severe headache, confusion, vision changes, and dizziness [1.4.4]. Likewise, significant internal bleeding in the gastrointestinal tract or elsewhere can lead to a drop in blood pressure and red blood cell count (anemia), causing symptoms like dizziness, weakness, fatigue, and pale skin [1.8.1, 1.8.2].

Signs of Serious Bleeding to Watch For:

If you experience dizziness along with any of the following symptoms, seek immediate medical attention [1.2.2, 1.4.5]:

A sudden or very bad headache
Feeling very weak or tired
Unusual or excessive bruising
Black, tarry, or bloody stools
Red or dark brown urine
Coughing up blood or vomit that looks like coffee grounds
Nosebleeds or bleeding from gums that won't stop
Any fall or head injury, even without visible bleeding

Managing Warfarin and Its Side Effects

Proper management is key to minimizing risks while on warfarin. This involves a partnership between the patient and their healthcare provider.

Regular INR Monitoring: Adhering to the schedule for blood tests is non-negotiable to keep your INR in the target range [1.2.2].
Consistent Diet: Vitamin K can make warfarin less effective. It's important to maintain a consistent intake of vitamin K-rich foods like leafy green vegetables (spinach, kale, broccoli) rather than making sudden changes to your diet [1.7.1].
Drug and Supplement Interactions: Many over-the-counter medications (like aspirin, ibuprofen), prescription drugs, and herbal supplements (like St. John's Wort, ginkgo biloba, garlic) can interact with warfarin and increase bleeding risk [1.7.1, 1.7.4]. Always consult your doctor before starting any new medication or supplement.
Limit Alcohol: Alcohol can increase warfarin's effect and raise the risk of bleeding [1.5.1].
Safety Precautions: To prevent injuries that could lead to bleeding, use a soft toothbrush, shave with an electric razor, and be cautious with activities that have a high risk of falls or injury [1.5.3].

Comparison: Warfarin vs. Newer Anticoagulants (DOACs)

In recent years, a newer class of blood thinners called Direct Oral Anticoagulants (DOACs) has become available. These include drugs like apixaban (Eliquis), rivaroxaban (Xarelto), and dabigatran (Pradaxa). They offer alternatives to warfarin with some distinct differences.


Feature	Warfarin (Coumadin, Jantoven)	Direct Oral Anticoagulants (DOACs)
Monitoring	Requires frequent INR blood tests [1.2.2].	Generally do not require routine blood monitoring [1.8.1].
Dietary Interactions	Significant interactions with vitamin K-rich foods [1.7.1].	No major dietary restrictions.
Drug Interactions	Many drug and supplement interactions [1.7.1].	Fewer drug interactions, but they still exist.
Risk of Bleeding	Higher risk of certain types of bleeding, like intracranial [1.6.1].	Generally lower risk of intracranial bleeding compared to warfarin [1.6.4].
Antidote	Reversal agent (Vitamin K) is widely available.	Specific reversal agents are available but may be less accessible or more costly.

Studies have shown that DOACs are associated with a lower risk of stroke and intracranial bleeding compared to warfarin [1.6.1, 1.6.4].

Conclusion

So, can warfarin cause dizziness? Yes, it is a recognized potential side effect. However, it is critically important to distinguish between benign, transient dizziness and dizziness that signals a medical emergency like severe bleeding. Any instance of dizziness, especially if it is new, persistent, or accompanied by other signs of bleeding or neurological changes, must be reported to a healthcare provider immediately. Proactive management, including regular monitoring, dietary consistency, and awareness of interactions, is essential for safely using this effective but powerful medication. For more information on managing warfarin, the Mayo Clinic provides comprehensive resources.

Frequently Asked Questions

If you feel dizzy, especially if it's severe, sudden, or accompanied by other symptoms like a bad headache, weakness, or signs of bleeding, you should seek immediate medical attention as it could be a sign of a serious complication [1.2.2, 1.4.5]. For mild, occasional dizziness, you should still inform your doctor.

Yes, dizziness, especially when severe or accompanied by feeling very weak, can be a symptom of a warfarin overdose, which causes excessive bleeding [1.4.1, 1.4.2].

While diet itself doesn't directly cause dizziness, sudden major changes in your intake of vitamin K (found in leafy greens) can make your warfarin dose less effective or too strong, potentially leading to complications that could cause dizziness. Consistency is key [1.7.1].

Dizziness is listed as a 'less common' or 'rare' side effect of warfarin. It is not one of the most frequent side effects, but it is a recognized possibility [1.2.1, 1.2.4].

An INR (International Normalized Ratio) test is a blood test that measures how long it takes your blood to clot. It's crucial for warfarin users to ensure the medication is working correctly and to adjust the dose to prevent both clotting and excessive bleeding [1.2.2].

Newer anticoagulants called DOACs (like Eliquis, Xarelto) are alternatives to warfarin. While all anticoagulants carry a risk of bleeding which can cause dizziness, DOACs generally have a lower risk of brain bleeds and don't require the same level of monitoring [1.6.1, 1.8.1]. Dizziness can still be a side effect of these medications [1.8.4].

It is best to limit alcohol. Both alcohol and warfarin can increase your risk of bleeding. Binge drinking can dangerously increase your INR, while chronic use might decrease it, making your dose unstable [1.5.1, 1.7.3].