For many of us, a morning doesn’t officially begin until we’ve had that first sip of coffee. It fuels our focus, sharpens our senses, and helps shake off the fog of sleep. But while coffee comes with its fair share of health perks—from antioxidants to improved alertness—it can also stir up problems when combined with certain medications.
According to Jennifer Bourgeois, Pharm.D., a clinical pharmacist, coffee can interfere with how some medications are absorbed, metabolized, or even how long they stay active in the body. The issue often stems from caffeine’s influence on digestive speed or its interaction with liver enzymes—especially CYP1A2, a key enzyme responsible for breaking down many drugs and caffeine itself.
If you’re on any of the following seven medications, you may want to reconsider when and how you enjoy your brew. Here’s what you need to know.
1. Antidepressants
If you’re taking antidepressants—especially ones like escitalopram (Lexapro), clomipramine, or imipramine—coffee might be sabotaging your treatment without you even realizing it.
Caffeine can hinder the body’s ability to absorb certain antidepressants. In the case of escitalopram, it may bind with the drug in your stomach, limiting its effectiveness. Others, such as clomipramine and imipramine, share a metabolic pathway with caffeine. That means both substances compete for the same liver enzymes, potentially causing your medication to linger longer in your bloodstream. This might lead to intensified side effects or, paradoxically, heightened caffeine sensitivity, making you feel jittery, anxious, or restless.
2. Thyroid Medications
People managing hypothyroidism typically take levothyroxine to maintain balanced hormone levels. However, if you pair your thyroid pill with a steaming mug of coffee, you may be reducing the drug’s effectiveness by up to 50%.
“Coffee interferes with levothyroxine’s absorption in the stomach,” says Bourgeois. “This can lead to persistent fatigue, brain fog, or other symptoms of underactive thyroid despite consistent medication use.” The general recommendation? Wait at least 30 to 60 minutes after taking your thyroid pill before drinking coffee.
3. Osteoporosis Medications
Medications like alendronate and risedronate, commonly prescribed to strengthen bones, are notoriously finicky about how they’re taken. Coffee, juice, milk—or even decaf—can all block their absorption.
“Always take these medications with plain water on an empty stomach,” Bourgeois advises. Any deviation can drastically reduce the medication’s ability to be absorbed, making it far less effective in preventing bone loss.
4. Cold & Allergy Medications
If you reach for pseudoephedrine (the active ingredient in Sudafed) during allergy season, pairing it with coffee might make you feel more wired than relieved. That’s because both pseudoephedrine and caffeine are stimulants—and when taken together, they can amplify each other’s side effects.
This can lead to increased heart rate, anxiety, shakiness, and even elevated blood sugar—especially in people with diabetes. Bourgeois cautions that it’s best to stagger your coffee and medication, or at the very least, keep your caffeine intake modest while on these types of meds.
5. Antipsychotic Medications
Coffee’s effects can be especially pronounced for people taking antipsychotics like clozapine, olanzapine, haloperidol, or phenothiazines. These medications depend on the same liver enzymes as caffeine to be broken down.
In one study, blood levels of clozapine rose by 97% after consuming just two to three cups of coffee. That kind of increase can make side effects more intense and raise safety concerns. If you’re on these medications, speak with your provider about whether limiting caffeine—or spacing it out—is necessary.
6. Asthma Medications
Bronchodilators such as aminophylline and theophylline are used to help people with asthma breathe easier by relaxing airway muscles. However, they already carry a risk of side effects like insomnia, irritability, and nausea—all of which can be worsened by caffeine.
When caffeine is added to the mix, those effects can be amplified. “If you’re on these medications, it’s smart to monitor how much caffeine you’re consuming and adjust if needed,” says Bourgeois. Consider switching to lower-caffeine beverages or reducing your intake if symptoms persist.
7. Blood Thinners
Blood thinners, including aspirin, warfarin, and others prescribed after surgery or for heart conditions, work by reducing the blood’s ability to clot. Coffee, with its natural blood-thinning effect, can further increase the risk of excessive bleeding or bruising.
Moreover, the acidity of coffee may accelerate how quickly certain blood thinners are absorbed, potentially delivering too much of the drug at once. This interaction can intensify the medication’s effects beyond what’s safe or intended.
Final Thoughts
A hot cup of coffee can be comforting, energizing, and even good for you—but it doesn’t always play nicely with medication. From altering absorption to competing in your liver’s metabolic queue, coffee can undermine the very medicines you rely on to stay healthy.
You don’t necessarily need to give it up—but being mindful about timing is key. “Spacing out your medications and coffee by at least 30 to 60 minutes is often enough to reduce most interactions,” says Bourgeois.
Still, every person’s body responds differently, and drug interactions can be complex. If you’re unsure whether your medications are affected by coffee—or any other food or drink—talk to your pharmacist or healthcare provider. It’s a simple step that could make a big difference in how well your treatment works.
