Coffee and Medications That Don’t Mix Well
Nutrition & FitnessDiet & Nutrition

10 Medications That Don’t Mix Well With Coffee

From thyroid medications to antidepressants, coffee can interfere with how your body processes certain prescription or over-the-counter medications. Here’s how to safely manage both.

10 Medications That Don’t Mix Well With Coffee
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Published on October 17, 2025
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Coffee may be such an established ritual in your life that having your morning brew has become as second nature as brushing your teeth. However, when you take over-the-counter (OTC) medications or prescription drugs, it’s important to pause to consider how they may interact with your daily coffee habit.

Most coffee-drug interactions are due to caffeine, the compound that gives coffee its stimulating effects. “Caffeine is rapidly and almost completely absorbed in the gastrointestinal tract, with peak blood concentrations occurring within 15 minutes to two hours after ingestion,” says Emmanuel Osei-Boamah, MD, a primary care physician with Mercy Family Care in Baltimore. That means coffee and medications can interact quickly when taken close together.

However, coffee contains other compounds that can also affect how your body metabolizes certain medications.

1. Antidepressants

Caffeine can interfere with certain antidepressants — in particular, those that are broken down in the liver by the CYP1A2 enzyme (a protein that speeds up chemical reactions). Those include fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), and duloxetine, a serotonin norepinephrine reuptake inhibitor.

 That’s because CYP1A2 also plays a crucial role in the breakdown of caffeine. So, drugs broken down by this enzyme share the same metabolic pathway and can alter the metabolism of caffeine — and vice versa.

Caffeine can also slow the metabolism of certain SSRIs, including fluoxetine and escitalopram, sometimes boosting their effects as a result. That may enhance the effects of the antidepressant and exacerbate medication symptoms (such as restlessness, appetite changes, and upset stomach).

In addition, combining monoamine oxidase inhibitors (MAOIs) such as tranylcypromine and phenelzine, with too much caffeine can raise the risk of high blood pressure (hypertension).

That’s because caffeine can have exaggerated effects in those taking MAOIs, causing hypertension along with tremor (continuous, involuntary shaking or trembling), heart palpitations, anxiety, or poor sleep.

Osei-Boamah recommends separating your coffee and antidepressant consumption by at least one to two hours to minimize the risk of interactions.

2. Cold and Allergy Medications

The stimulant effect of caffeine doesn’t pair well with many cold and allergy medicines. “Many cold medications, especially those with decongestants like pseudoephedrine, already increase heart rate or blood pressure,” says Kennedy Erickson, PharmD, a pharmacist with Centralia Pharmacy in Centralia, Washington, and a member of the American Pharmacists Association.

Adding caffeine can compound those effects, leading to heart palpitations or anxiety, Dr. Osei-Boamah adds.

Whether you’re taking OTC cold and allergy medications or prescription ones, it’s important to talk to your doctor about the potential side effects of combining them with coffee.

3. Thyroid Medicines

Research shows that certain polyphenols in coffee bind to molecules in the gut, making it difficult for the intestines to absorb levothyroxine, a hormone medication that’s used to treat hypothyroidism (a condition that happens when the thyroid gland doesn’t make enough thyroid hormones).

 In fact, research shows that people who stop drinking coffee when taking levothyroxine see a marked improvement in thyroid hormone control.

Erickson recommends taking levothyroxine on an empty stomach with water and waiting at least 30 to 60 minutes before drinking coffee. “It’s a simple timing fix that can make a big difference for thyroid control,” she says.

4. Diabetes Medications

Experts generally advise caution when mixing coffee and diabetes medications, since coffee can have the opposite effect of antidiabetic drugs like glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), and rosiglitazone (Avandia).

“Caffeine can raise blood sugar levels in some individuals by triggering stress hormone release, which counteracts what many diabetes medications are trying to achieve,” says Erickson. “That said, the effect varies by individual, as some people are more sensitive to caffeine than others.”

The interaction between coffee and diabetes medication is complex. It depends on the effects of the caffeine and polyphenols (the main active ingredients in coffee) and your specific diabetes medication, adds Osei-Boamah.

If you have diabetes, monitor your blood sugar closely for unexpected fluctuations after drinking coffee, suggests Erickson. If you notice these fluctuations, talk with your healthcare team to discuss potential changes in your diabetes management plan, which may include the timing or amount of coffee you drink.

5. Blood Pressure Medications

Caffeine can temporarily raise blood pressure, which may dampen the effectiveness of blood pressure medications. “This effect is most pronounced within the first one to three hours after ingestion,” says Osei-Boamah, noting that caffeine can raise systolic blood pressure (the pressure in your arteries when your heart contracts) by approximately 5 to 8 millimeters of mercury (mmHg) and diastolic blood pressure (the pressure in your arteries when your heart relaxes) by 4 to 6 mmHg, in sensitive individuals.

However, your blood pressure may even out with regular coffee consumption, once your body gets accustomed to the caffeine. Research indicates that the effects of caffeine on blood pressure are most pronounced in younger people and with short-term use.

Still, if you’re taking blood pressure medication, your doctor may recommend avoiding caffeine altogether. “While it may not cancel out a blood pressure medication entirely, it can make control more difficult,” Erickson explains.

6. Osteoporosis Medications

Caffeine can significantly lower the absorption of oral bisphosphonates (such as alendronate, risedronate, and ibandronate), the first-line medications for osteoporosis (a bone-weakening disease), and, as a result, their bioavailability (the amount of the medicine that is available to the body), says Osei-Boamah.

“It’s recommended that oral bisphosphonates be taken with plain water only, at least 30 to 60 minutes before consuming coffee, other beverages, food, or supplements, to maximize absorption and clinical benefit,” adds Osei-Boamah.

One exception is the delayed-release formulation of risedronate, which is designed to be taken after breakfast with minimal impact on absorption and bioavailability, Osei-Boamah adds.

7. Melatonin

The way caffeine interacts with melatonin (the supplement form of a natural hormone that signals the body to prepare for sleep) is relatively straightforward. As a stimulant, caffeine counteracts melatonin’s sleep-promoting effects and delays its production, says Erickson.

Avoid drinking coffee and other caffeinated beverages with melatonin.

 In fact, it’s best to cut off your coffee intake by midafternoon if you take melatonin to help with sleep, since coffee can make the melatonin less effective, Erickson says.

8. Alzheimer’s Medications

Caffeine may prevent the blood-brain barrier (a layer of cells that protects your brain from certain substances) from opening enough to allow donepezil and memantine, medications used to treat Alzheimer’s disease (a brain disorder that causes memory loss and confusion), to pass through.

“When paired with cholinesterase inhibitors like donepezil, coffee could decrease how much of the medication makes it into the brain, because it competes with its mechanism,” says Erickson. Coffee and other sources of caffeine can tighten the blood-brain barrier, so drugs that usually cross it to have an effect on the brain may not be able to pass through as well.

9. Asthma Medications

Asthma medications relax your airway muscles to make breathing easier. Drinking coffee can increase medication side effects, including nausea, headache, irritability, and restlessness.

“This is particularly true of theophylline, which is chemically similar to caffeine [both are stimulants],” says Erickson. “When taken together, they can lead to additive side effects like tremor, rapid heartbeat, or nausea. Even with inhalers like albuterol, caffeine may increase stimulation.”

10. Blood Thinners

Animal research suggests that caffeine can inhibit the metabolism of warfarin (an anticoagulant medication commonly prescribed to prevent or treat blood clots), causing it to linger in the blood.

 This may enhance the effects of blood thinners, leading to an increased risk of bleeding, says Erickson. However, it’s unclear whether the same effect seen in animal studies would be produced in humans. Additional research is needed.
Research also suggests that warfarin resistance (the inability to absorb the medication properly) may be reversed by reducing caffeine intake, though this is based on case studies involving only three patients. More research is needed to confirm these findings.

The consistency of your coffee intake may impact whether you experience interactions. “If you take warfarin and drink a cup of coffee daily, that should not dramatically change how quickly blood clots,” Erickson says. “But adding a cup or two [more] a day could, so it’s important to track this.”

Coffee does not directly interact with newer blood thinners, such as apixaban or rivaroxaban, she adds.

When to See a Doctor

Talk to your doctor or pharmacist if you have questions about how coffee may interact with your medications, or if you experience side effects such as jitters, sleep disturbances, a fast heartbeat, blood sugar changes, or any other unusual symptoms. Your doctor can provide advice tailored to your specific medication.

“Sometimes, it’s not about eliminating coffee — it’s about spacing it properly,” says Erickson. You may be able to avoid interactions by adjusting the timing of your coffee and medications. However, some people may need to avoid coffee altogether.

It’s best to consult your healthcare provider for personalized recommendations tailored to the medicines you take, your sensitivity to caffeine, and any symptoms you experience.

The Takeaway

  • Certain compounds in coffee, such as caffeine and polyphenols, can speed up or slow down the absorption of medications and increase your risk of adverse effects.
  • Coffee may interact with several prescription and OTC medications, including antidepressants, blood thinners, cold and allergy medicines, melatonin, and more.
  • See your doctor if you take medication with coffee and experience side effects such as jitters, sleep disturbances, rapid heartbeat, blood sugar changes, or other unusual symptoms. Your doctor can provide tailored advice about medication timing and cutting back on coffee or eliminating it altogether.
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Kristina D. Carter, PharmD

Medical Reviewer

Kristina D. Carter, PharmD, is a clinical pharmacist and freelance health writer who currently works in a managed care setting, performing quality audits on utilization management case reviews for the pharmacy team. She has over 20 years of experience and has worked in several pharmacy practice settings, including at a community pharmacy as well as in ambulatory care, senior care, and pharmacy operations.

She received her doctor of pharmacy degree from Xavier University of Louisiana College of Pharmacy and her master's of business administration and health administration from Georgia State University Robinson College of Business. She is an American Council on Exercise–certified health coach, group fitness instructor, senior fitness specialist, and weight management specialist. She is also a registered pharmacist, licensed in Georgia, Indiana, and Tennessee.

Dr. Carter enjoys exploring new restaurants with family and friends, walking along city trails, and watching action movies and college sports.

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Kelsey Kloss is a health and wellness journalist with over a decade of experience. She started her career as an in-house editor for brands including Reader’s Digest, Elle Decor, Good Housekeeping, Prevention, Woman's Day, and Redbook, and her work has been featured in over 50 publications.

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