When you take warfarin, a blood thinner used to prevent dangerous 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, which your body needs to form clots. But if you’re also using CBD, a non-intoxicating compound from cannabis that’s widely used for pain, anxiety, and sleep, things get complicated. CBD affects the same liver enzymes—CYP2C9 and CYP3A4—that break down warfarin. That means CBD can slow down how fast your body clears warfarin, causing levels to build up in your blood.
This isn’t theoretical. Real cases have shown people on stable warfarin doses suddenly developing dangerously high INR levels after starting CBD. One patient’s INR jumped from 2.5 to 8.1 within days of adding a daily CBD oil—leading to nosebleeds and bruising. That’s not a coincidence. The CYP450 enzyme system, the body’s main drug-processing network is easily disrupted by CBD, just like it is by grapefruit juice or certain antibiotics. And unlike those, CBD isn’t always labeled with warnings. Many people assume it’s "natural," so it must be safe. But natural doesn’t mean harmless, especially when you’re on a drug where a tiny change in dose can mean the difference between a clot and a stroke.
There’s no safe dose of CBD to mix with warfarin without medical supervision. Even low amounts can interfere. If you’re on warfarin and considering CBD, talk to your doctor first. Don’t just start taking it because you saw a post online. Your INR needs to be checked more often—maybe weekly—until things stabilize. And if you’re already using CBD, don’t quit cold turkey. Sudden changes can also throw off your clotting levels. The goal isn’t to scare you, but to make sure you’re not walking into a risk blindfolded. Below, you’ll find real stories and science-backed advice from people who’ve navigated this exact issue—what worked, what didn’t, and what your doctor needs to know before you make a move.
Cannabis can interfere with common medications like warfarin, clobazam, and opioids, leading to dangerous side effects. Learn which drug interactions are high-risk, how to stay safe, and what to do if you're already using both.
