Warfarin Interactions: What You Need to Know About Drugs, Foods, and Supplements

When you take warfarin, a blood thinner used to prevent clots in people with atrial fibrillation, artificial heart valves, or a history of deep vein thrombosis. Also known as Coumadin, it works by blocking vitamin K’s role in clotting—but that’s also what makes it so easy to mess up. Even small changes in your diet, other meds, or supplements can throw off your INR levels, a blood test that measures how long it takes your blood to clot. Too high, and you risk bleeding. Too low, and you could get a stroke or clot. It’s not guesswork—it’s precision.

Many people don’t realize how many things interact with warfarin. Milk thistle, a popular liver supplement, can interfere with how your liver breaks down warfarin, making levels unpredictable. Same with green coffee extract, often taken for weight loss or blood pressure—its caffeine and other compounds can alter how warfarin works. Even over-the-counter painkillers like ibuprofen or aspirin can increase bleeding risk. And it’s not just pills: vitamin K-rich foods, like kale, spinach, broccoli, and Brussels sprouts, directly oppose warfarin’s effect. You don’t have to avoid them completely, but you need to eat them consistently. A big salad one day and none the next? That’s a recipe for unstable INR.

It’s not just about what you take—it’s about what you stop taking. Antibiotics, antifungals, even some herbal teas can change how your body handles warfarin. That’s why your pharmacist should always know everything you’re using. The warfarin interactions list is long, and many aren’t obvious. One study found nearly 40% of people on warfarin had at least one risky interaction they didn’t know about. That’s why regular INR checks aren’t optional—they’re your safety net.

You’ll find posts here that dig into real-world examples: how milk thistle affects liver enzymes tied to warfarin, why green coffee extract can cause dangerous swings, and what foods actually matter most. There’s also advice on how to talk to your doctor about supplements, how to spot early signs of bleeding, and why some generic meds aren’t always interchangeable when you’re on warfarin. This isn’t theory—it’s what keeps people out of the ER. If you’re on warfarin, or care for someone who is, this collection gives you the clear, no-fluff facts you need to stay safe every day.