THC Interactions: What You Need to Know About Cannabis and Medications
When you take THC, the main psychoactive compound in cannabis that affects the brain and body. Also known as tetrahydrocannabinol, it can interfere with how your body processes other drugs—especially those handled by the liver’s CYP enzyme system. This isn’t theoretical. People on blood thinners, antidepressants, or seizure meds have ended up in the ER because THC changed how their pills worked. It’s not about being ‘high’—it’s about chemistry.
THC interacts with the same liver enzymes—CYP2C9, a key enzyme that breaks down drugs like warfarin and NSAIDs and CYP3A4, the most common enzyme involved in drug metabolism—as many prescription medications. That means if you’re on warfarin, your INR could spike. If you’re taking statins, you might get muscle damage. If you’re on SSRIs, your side effects could get worse. These aren’t rare cases. Studies show THC can boost blood levels of some drugs by over 30%, and those effects last longer than people expect.
It’s not just about pills. Grapefruit, a well-known offender in drug interactions works the same way as THC—blocking those liver enzymes. That’s why the same warnings apply: if your doctor told you to avoid grapefruit with your meds, you should probably avoid THC too. And it’s not just adults. Teens using cannabis for anxiety or sleep might be unknowingly messing with their ADHD or antidepressant meds. Older adults on multiple prescriptions are at the highest risk, especially if they’re using edibles, which deliver THC slowly and unpredictably.
What you’ll find below isn’t a list of myths. These are real stories from people who didn’t know THC could turn a safe dose into a dangerous one. You’ll see how THC interactions show up in blood pressure meds, painkillers, sleep aids, and even insulin. Some posts explain why a simple joint can make your warfarin more dangerous. Others show how athletes using medical cannabis accidentally failed drug tests—not because of THC itself, but because of how it changed their other meds. There’s even one about how someone’s anxiety meds stopped working after they started using CBD oil—because the THC in it messed with their liver’s ability to process the drug.
These aren’t warnings against cannabis. They’re warnings about ignorance. If you’re taking any medication—prescription, over-the-counter, or even a supplement like quercetin or lithium—you need to know how THC fits into that picture. The answers are here. You just need to read them before something goes wrong.
