Questions to Ask Your Pharmacist About Potential Drug Interactions

Every year, over a million people in the U.S. end up in the emergency room because of unexpected reactions between their medications. Many of these cases aren’t accidents-they’re preventable. The biggest reason? People don’t ask the right questions when they pick up their prescriptions. Your pharmacist isn’t just the person who hands you your pills. They’re your last line of defense against dangerous drug interactions. And you need to treat them like one.

What exactly is a drug interaction?

A drug interaction happens when something changes how a medication works in your body. It could be another pill, a food, a supplement, or even a drink. These changes can make your medicine too strong, too weak, or cause side effects you didn’t expect. Some interactions are mild-like a stomach upset. Others can be life-threatening. For example, taking warfarin (a blood thinner) with too much vitamin K from leafy greens can make it less effective, raising your risk of a clot. Or mixing grapefruit juice with certain statins can cause muscle damage. The FDA says over 112,000 serious adverse events linked to drug interactions were reported in 2022 alone. Most involved heart meds, diabetes drugs, or anticoagulants.

What should you ask your pharmacist before leaving the counter?

You don’t need to be a doctor to spot red flags. Start with these five essential questions every time you get a new prescription-or even refill an old one.

1. Can this medicine interact with anything else I’m taking? This includes everything: prescription drugs, over-the-counter painkillers, cold meds, sleep aids, vitamins, herbal supplements, and even CBD. Many people forget about the supplements. St. John’s wort, for instance, can make birth control, antidepressants, and even some cancer drugs stop working. A 2022 survey found that 77% of American adults take at least one supplement. Most have no idea how risky that can be.
2. Should I avoid any foods, drinks, or alcohol? Grapefruit juice is the most famous culprit-it blocks enzymes that break down over 85 medications, including some blood pressure pills and cholesterol drugs. But it’s not the only one. Aged cheeses, cured meats, and red wine can spike blood pressure if you’re on an MAO inhibitor like phenelzine. Alcohol can make sedatives, painkillers, and even antibiotics dangerously strong. Ask specifically: “Is there anything I can’t eat or drink while on this?”
3. Will this affect my existing health conditions? A common mistake is assuming a new drug is safe just because your doctor prescribed it. But if you have high blood pressure, an over-the-counter decongestant can send your numbers soaring. If you have kidney disease, some antibiotics or NSAIDs can worsen it. The American Heart Association says patients with hypertension should always ask: “Is this safe with my heart condition?”
4. When and how should I take this? Timing matters. Some meds need to be taken on an empty stomach. Others work better with food. Taking them at the wrong time can change how much gets absorbed-or cause interactions. For example, taking thyroid medicine with calcium or iron supplements can block absorption. The label says “take on an empty stomach”? Ask what that actually means. “Two hours before or after meals?” “Can I have coffee?”
5. What signs should I watch for if something’s wrong? You need to know what’s normal and what’s not. Dizziness, unusual bruising, rapid heartbeat, muscle pain, or sudden confusion could signal a problem. The FDA says patients should be told exactly what symptoms mean “stop this medicine and call your pharmacist or doctor.” Don’t wait for a crisis. Ask for a list of warning signs.

Why your medication list matters more than you think

Pharmacists don’t magically know what you’re taking. They rely on what you tell them. And most people don’t give complete info. A 2021 study showed that patients forget or misreport about 40% of their medications-including supplements and OTCs. That’s why bringing a written list is non-negotiable. Write down:

• The name of each medicine
• The dose (e.g., 10 mg, 500 mg)
• How often you take it (e.g., once daily, every 8 hours)
• Why you take it (e.g., “for blood pressure,” “for arthritis”)

Don’t just say “I take my pills.” Say: “I take metformin 500 mg twice a day for diabetes, lisinopril 10 mg once a day for blood pressure, and I also take a magnesium supplement every night.” The more detail, the better. Pharmacists use this to check for interactions using systems that flag risks like CYP3A4 or CYP2C19 enzyme conflicts-things like rifampin or carbamazepine making your meds less effective.

What about supplements and herbal products?

They’re not harmless. “Natural” doesn’t mean safe. Many herbal products interfere with how your body processes drugs. St. John’s wort speeds up the breakdown of antidepressants, birth control, and even some heart meds. Garlic and ginkgo can thin your blood, which is dangerous if you’re on warfarin or before surgery. Kava can damage your liver when mixed with alcohol or acetaminophen. Rita Shane, PharmD, says: “Some of these products can cause side effects such as bleeding, interfere with absorption of other drugs, or have effects on how the drugs are eliminated from your system.”

What if you’re on five or more medications?

You’re not alone. Nearly half of adults over 65 take five or more daily medications. That’s called polypharmacy-and it’s where most serious interactions happen. The more pills you take, the higher the risk. The American Society of Health-System Pharmacists says pharmacists should review all your meds every time you visit. But they can’t do it if you don’t bring the list. If you’re on multiple drugs, ask for a medication therapy management (MTM) session. These are free for many Medicare patients and can reduce interaction-related ER visits by over 23%.

What’s new in drug interaction screening?

Pharmacies now use electronic systems that flag interactions in real time. CVS and Walgreens have had them since 2021. But here’s the catch: they only work if your full medication history is in the system. If you fill a prescription at a different pharmacy, or if you take supplements not tracked in their database, the system misses them. A 2022 JAMA study found these tools still miss about 18% of dangerous interactions. That’s why your input matters more than ever.

How often should you talk to your pharmacist?

Don’t wait until something goes wrong. Make it a habit. Ask for a quick review every time you get a new prescription. Even if you’re just refilling, say: “Is this still safe with everything else I’m on?” If you’re on multiple meds, schedule a full review every three to six months. The most common cause of a new interaction? The last drug added. That’s usually the one you didn’t think about.

What if you’re unsure about a label?

Medication labels have sections like “Warnings,” “Drug Interactions,” and “Other Information.” But they’re written for doctors, not patients. If you see something confusing-like “avoid strong CYP3A4 inducers”-don’t guess. Ask. Ask what that means in plain language. Ask if your other meds fall into that category. The FDA says patients should always ask: “Is there more information available about this drug?” There is. Your pharmacist is the one who can give it to you.

What’s the bottom line?

Drug interactions aren’t rare. They’re common-and often avoidable. The system isn’t perfect. Electronic alerts miss things. Doctors don’t always know about your supplements. But your pharmacist? They’re trained to catch what others miss. You just have to speak up. Bring your list. Ask the five questions. Don’t assume anything is safe. And never, ever skip a refill check-in. Your life might depend on it.