This Supplement May Make Medications Less Effective

Thanks to their medicinal qualities, herbs and spices have been used for thousands of years to treat and prevent illness. One of those spices is cinnamon, which research suggests may help lower cholesterol and reduce blood pressure. There is also evidence that it supports healthy blood sugar levels. And because cinnamon has a natural sweetness, a sprinkle of it can be used in place of sugar to sweeten up your bowl of oatmeal or add a flavor boost to your morning joe. 

But herbs and spices also come with some caution. Because they can have medicinal properties, it’s important to understand how they may interact with your body and the medications you take. 

Researchers at the University of Mississippi simulated an intestinal environment in the laboratory to test cinnamon’s bioaccessibility, or the amount that becomes accessible for absorption in the digestive tract after ingesting it. They also tested its metabolism—how it’s broken down in the body—and how it interacts with xenobiotic receptors. Those are specialized receptors in the body that sense and respond to foreign chemicals, which, in this case, is the cinnamon. 

They published their findings in 2025 in Food Chemistry: Molecular Sciences. Let’s break down what they found. 

How Was This Study Conducted? 

Researchers simulated an intestinal environment in the lab using gastric (stomach) acid,  liver and intestinal cells and enzymes. They tested various components of cinnamon in environments that mimicked fasting and fed states, since our intestinal environments change depending on whether we’ve eaten or not. 

The components of cinnamon include cinnamon oil, cinnamaldehyde and cinnamic acid. Each was added to the various simulations, mixed and incubated for varying amounts of time, then examined.

What Did This Study Show?

Researchers found that cinnamaldehyde moderately activated the xenobiotic receptors. This means that it could potentially trigger an herb-drug interaction, interfering with the absorption and effectiveness of medications. 

“Overconsumption of [cinnamon] supplements could lead to a rapid clearance of prescription medicine from the body, and that could result in making the medicine less effective,” says Shabana Khan, Ph.D., one of the study’s authors, in a press release.

Like all studies, this one comes with some limitations you should be aware of. Importantly, the study was conducted in the lab, not on humans. While researchers can attempt to simulate a human environment, they cannot perfectly mimic it. The conclusion that cinnamon more quickly clears medication from the body is a hypothesis based on the study results, but it is not yet proven. 

“We know there’s a potential for cinnamaldehyde to activate these receptors that can pose a risk for drug interactions,” says Bill Gurley, Ph.D., another one of the researchers, in the press release. “That’s what could happen, but we won’t know exactly what will happen until we do a clinical study [on humans].”

How Does This Apply to Real Life?

Researchers note that cinnamon oil, which is commonly used as a flavoring in foods and as an essential oil, poses almost no risk of herb-drug interactions. Nor does Ceylon, which is sometimes called “true cinnamon.” Large amounts of cassia cinnamon, however, should be used with caution. 

Cassia cinnamon is the type most commonly sold in the U.S. It comes from Asia and is cheaper and has a stronger cinnamon flavor than Ceylon cinnamon, which originates from Sri Lanka.

Compared to Ceylon cinnamon, cassia cinnamon has also been shown to have a higher amount of coumarin, a substance known to act as a blood thinner. Frequently ingesting cassia cinnamon, whether in high amounts or as a supplement, could potentially pose a risk for those taking anticoagulant (blood thinner) medications, like warfarin (Coumadin), apixaban (Eliquis), clopidogrel (Plavix) or aspirin. 

These researchers recommend that anyone with a chronic disease—including high blood pressure, diabetes, cancer, arthritis, asthma, HIV, AIDS or depression—talk to their healthcare practitioner before taking cassia cinnamon as a supplement or regularly using it in high doses in food. 

Ultimately, it’s all about balance. Even the healthiest foods can become harmful when taken in high doses. If you’re contemplating taking cinnamon supplements—or you already are—check in with your healthcare practitioner or pharmacist or meet with a registered dietitian to determine if that’s a safe route for you. 

“You don’t need to completely avoiding using cinnamon in your meals if you’re on medications,” senior nutrition editor Jessica Ball, M.S., RD, clarifies. “Most of the research about cinnamon impacting medication absorption looked at cinnamon oils or concentrations of cinnamaldehyde that are higher than what’d you typically get from consuming it as a spice. That said, it’s a good reminder to use a moderate amount of spices and to be cautious when considering dietary supplements, even if they’re a familiar nutrient or spice.”

If you’re going to regularly use cinnamon in your food and beverages, it might be safest to use Ceylon cinnamon—or keep cassia consumption to under 1 teaspoon per day. It’s also important to note that some manufacturers “cut” their cassia cinnamon with fillers, like those to help prevent caking of the product. So what you sprinkle out of your spice bottle might not be all cassia.

Unfortunately, the FDA doesn’t differentiate between the two types of cinnamon, but companies that sell true Ceylon cinnamon will put it on the label. If it doesn’t say Ceylon, you can assume it’s cassia. 

We love using cinnamon in baked goods, like our Cinnamon Swirl Apple Pie and Cinnamon Streusel Banana Bread. It also adds a warm sweetness to our Cranberry-Apple Relish and perfectly complements the chocolate in our Chicken with Quick Mole Sauce—so don’t feel like you have to give it up.

The Bottom Line

This study suggests that cassia cinnamon, which has higher levels of cinnamaldehyde than Ceylon cinnamon, may sweep medications out of the body too quickly. Thus, it might not allow the medication enough time to perform its functions.

While more research needs to be done on this topic, it does add to the evidence promoting caution with Cassia cinnamon, since we already know that it acts as a blood thinner. If you’re considering using a cinnamon supplement or you regularly use cinnamon in your food or beverages, consult with a medical professional, stick to no more than 1 teaspoon per day, and if possible, use Ceylon cinnamon.