Warfarin and Atorvastatin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 15, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Atorvastatin
Warfarin
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased warfarin exposure and an increased INR
Interaction Deep Dive
Coadministration of atorvastatin (CYP3A4 inhibitor) and warfarin (CYP3A4 substrate), may increase warfarin exposure and increase INR. Consider CYP3A4 inhibition potential when starting, stopping, or changing the dose of concomitant medications used during warfarin therapy. Closely monitor INR if atorvastatin is used with warfarin3. Coadministration of vitamin K antagonists with statin therapy (including atorvastatin) was associated with a minor increase in anticoagulant effect of VKAs in a systematic review of 8 studies 4. Statin therapy in combination with warfarin is beneficial when clinically appropriate. The impact on INR may be lower with atorvastatin (or pitavastatin) compared with other statins 2.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of warfarin
Literature reports
3 reports — tap to read
a) Coadministration of vitamin K antagonists (VKAs) with statin therapy was associated with a minor increase in anticoagulant effect of VKAs in a systematic review of 8 studies. Warfarin was the most commonly used VKA and simvastatin was the most commonly used statin within the studies. In patients receiving warfarin, initiation of simvastatin increased INR by 0.15 to 0.65. A similar effect of slightly increased anticoagulation (increased INR, reduced VKA doses, and increased risk of hospitalization for gastrointestinal bleeds) also occurred with other statins, including atorvastatin, rosuvastatin, and fluvastatin. Studies including pravastatin did not report an effect on anticoagulation. Due to significant heterogeneity between studies, a direct comparison by meta-analysis was not feasible 4.
b) In patients receiving warfarin, increased mean INR levels occurred following initiation of statin therapy in a register-based study. Concomitant use of warfarin with atorvastatin (n=165) significantly increased INR by 0.27 (95% CI, 0.12 to 0.42) and rosuvastatin (n=23) was associated with a non-significant INR increase of 0.3. In patients coadministered simvastatin (n=1363), mean INR increased significantly by 0.32 (95% CI, 0.25 to 0.38) and significantly more warfarin-treated patients had at least 1 INR greater than 4 during the 3 to 6 weeks after simvastatin initiation compared with 1 to 4 weeks before (9% vs 3.4%). INR values above 5 also significantly increased (3.2% vs 1.3%). Increase in INR associated with simvastatin use peaked at around 4 weeks following initiation. Patients were a median age of 70 to 74 years and 47% to 62% were male. This study was limited by the inability to address adherence or other factors that might increase INR, and the exact date of initiation or early discontinuation was not available 5.
c) Atorvastatin had no clinically significant effect on prothrombin time when administered to patients receiving chronic warfarin treatment 1.
Common questions
Can I take Warfarin and Atorvastatin together?
Increased warfarin exposure and an increased INR Always confirm with your pharmacist or prescriber before making any change.
How serious is the Warfarin and Atorvastatin interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
- Can I Take MacuShield Gold With Edoxaban, Atorvastatin, and Bisoprolol?
- Can I Take Ginkgo With Apixaban (Eliquis) and Atorvastatin?
- Is It Safe to Drink Motherwort Tea While Taking Atorvastatin?
- Are Blueberries Safe To Eat If You Take Warfarin?
- Does Ashwagandha Interact With Warfarin?
- Does Flaxseed Interact With Warfarin?
Questions for your pharmacist
- Does my dose of Warfarin or Atorvastatin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (5)
- Product Information: ATORVALIQ(R) oral suspension, atorvastatin calcium oral suspension. CMP Pharma Inc (per FDA), Farmville, NC, 2023. DailyMed
- Wiggins BS, Saseen JJ, Page RL, et al: Recommendations for management of clinically significant drug-drug interactions with statins and select agents used in patients with cardiovascular disease: a scientific statement from the American Heart Association. Circulation 2016; 134(21):e468-e495. PubMed
- Product Information: WARFARIN SODIUM oral tablets, warfarin sodium oral tablets. Teva Pharmaceuticals (per Dailymed), Parsippany, NJ, 2023. DailyMed
- Engell AE, Svendsen ALO, Lind BS, et al: Drug-drug interactions between vitamin K antagonists and statins: a systematic review. Eur J Clin Pharmacol 2021; 77(10):1435-1441. PubMed
- Engell AE, Svendsen ALO, Lind BS, et al: Drug-drug interaction between warfarin and statins: a Danish cohort study. Br J Clin Pharmacol 2021; 87(2):694-699. DOI
Keep reading about Atorvastatin
Keep reading about Warfarin
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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