Researchers in Iran visited 225 pharmacies pretending to be customers looking for joint pain supplements. They wanted to see if pharmacists would warn about dangerous interactions with common blood-thinning medications. The results were concerning: most pharmacists didn’t ask basic questions about the customer’s health or current medicines, and very few caught a serious interaction between a popular supplement and warfarin (a blood thinner). This study shows that people buying supplements for arthritis pain may not be getting the safety advice they need from their pharmacists.

The Quick Take

  • What they studied: Whether pharmacists in Iran properly counsel customers about joint supplements and warn about dangerous drug interactions
  • Who participated: 225 community pharmacies across Iran. Two female researchers pretended to be customers asking about supplements for knee pain, with one scenario involving a 64-year-old father taking a blood thinner medication
  • Key finding: Only 29 out of 225 pharmacists (about 13%) recognized a dangerous interaction between a popular joint supplement and warfarin, a common blood thinner. Most pharmacists didn’t even ask basic questions about the customer’s health or medications
  • What it means for you: If you’re taking supplements for joint pain, especially while on blood thinners or other medications, you may need to ask your pharmacist specific questions about safety rather than waiting for them to bring it up. This suggests pharmacists need better training on supplement safety

The Research Details

Researchers used a “mystery shopper” method, which is like a real-world test. Two women went to 225 different pharmacies and pretended to be customers. In the first visit, they asked for an avocado/soybean supplement for knee pain without mentioning any other details. The pharmacist’s response was recorded. In the second part of the scenario, if the pharmacist hadn’t asked about their health or medications, the shopper mentioned that the supplement was actually for her 64-year-old father who takes warfarin (a blood thinner). This allowed researchers to see if pharmacists would catch the dangerous interaction when given more information.

This approach is valuable because it shows what actually happens in real pharmacies, rather than what pharmacists say they would do in a survey. All conversations were recorded so researchers could carefully analyze what advice was given.

The study looked at whether pharmacists asked about the customer’s medical history, current medications, how to use the supplement, and whether they warned about interactions or side effects.

Pharmacists are often the last healthcare professional a patient talks to before using a supplement. They’re trained to spot dangerous combinations between supplements and medications. This study reveals whether that training is being used in real situations. Understanding the gap between what pharmacists should do and what they actually do helps identify where improvements are needed to keep patients safe.

The mystery shopper method is a strong way to study real-world behavior because pharmacists don’t know they’re being tested, so they act naturally. However, the study only tested one specific supplement and one specific drug interaction in one country, so results may not apply everywhere. The study doesn’t explain why pharmacists missed these interactions—whether it’s lack of knowledge, time pressure, or other factors. The sample size of 225 pharmacies is reasonably large for this type of study.

What the Results Show

The research found major gaps in how pharmacists handle supplement questions. Only 15 out of 225 pharmacists (about 7%) even asked who the supplement was for or about the customer’s medical history. This is concerning because knowing the patient’s age, health conditions, and medications is essential for safe recommendations.

When it came to spotting the dangerous interaction between the avocado/soybean supplement and warfarin, only 7 pharmacists caught it initially (about 3%). When the shopper provided more details about the father’s age and warfarin use, this number improved to 29 pharmacists (about 13%). However, this is still a very low rate for such an important safety issue.

Even more troubling: not a single pharmacist provided information about side effects, other potential interactions, or situations where the supplement shouldn’t be used. Only 7 pharmacists explained how to properly take the supplement, and only 9 gathered any medical history information.

The study revealed that pharmacists’ responses varied widely. Some provided minimal information, while others were more helpful. However, even the better-performing pharmacists didn’t provide comprehensive safety information. The fact that recognition of the drug interaction improved when more patient information was provided suggests that pharmacists might have the knowledge but aren’t consistently asking the right questions to apply it.

Similar studies in other countries have found comparable problems with supplement counseling. This suggests it’s a widespread issue, not unique to Iran. Previous research has shown that many patients don’t realize supplements can interact with medications, and they often expect pharmacists to catch these problems. This study confirms that expectation isn’t being met in many cases.

The study only tested one specific supplement and one specific drug interaction, so we can’t assume the results apply to all supplements or all medications. The study was conducted in Iran, and pharmacy practices may differ in other countries. Only two female mystery shoppers were used, so we don’t know if results would be different with male shoppers or different ages. The study doesn’t explain why pharmacists failed to ask questions or recognize interactions—it just documents that they did. Finally, we don’t know if this represents a typical day or if pharmacists were unusually busy or distracted during these visits.

The Bottom Line

If you’re considering taking supplements for joint pain, especially if you take any other medications (particularly blood thinners, blood pressure medications, or diabetes medications), have a detailed conversation with your pharmacist. Specifically ask: ‘Could this supplement interact with my current medications?’ and ‘Are there any side effects I should know about?’ Don’t assume the pharmacist will bring up these concerns—you may need to ask directly. This is a moderate-confidence recommendation based on this study showing pharmacists often don’t volunteer this information.

Anyone taking supplements for arthritis or joint pain should care about this research, especially if they also take prescription medications. People over 65, who often take multiple medications, should be particularly cautious. Healthcare providers should also care because this highlights a training gap. People who don’t take any other medications have lower risk, but it’s still good practice to discuss supplements with a pharmacist.

You should have this conversation with your pharmacist before starting any new supplement, not after. The safety concerns are immediate, not something that develops over time. If you’re already taking a supplement safely, there’s no urgent need to change, but it’s worth having the conversation at your next pharmacy visit.

Want to Apply This Research?

  • Track all supplements and medications you’re taking in one place, including the dose and frequency. Before adding any new supplement, use the app to review your current medication list and bring it to your pharmacist appointment to discuss potential interactions.
  • Create a reminder to have a detailed supplement safety conversation with your pharmacist before starting any new supplement. Use the app to document the pharmacist’s specific recommendations about timing, dosage, and any warnings they provide.
  • Set up a quarterly review in the app where you list all supplements and medications, then schedule a pharmacist check-in to confirm there are no new interactions or concerns. This creates accountability and ensures you’re getting professional safety oversight.

This research describes current pharmacy practices in Iran and highlights gaps in supplement counseling. It does not provide medical advice about which supplements are safe for you. Before starting any new supplement, especially if you take prescription medications, consult with your doctor or pharmacist. This is particularly important if you take blood thinners, blood pressure medications, diabetes medications, or other prescription drugs. Never stop taking prescribed medications or change supplement use without professional medical guidance. The findings of this study should not be interpreted as evidence that supplements are unsafe—rather, they show that professional guidance is important for safe use.