Supplements are among the most common over-the-counter products patients use, often with good intentions but mixed results. Pharmacists are in a unique position to help patients and providers make sense of these products and prevent unnecessary harm or wasted money. Here are some of the top patient mistakes with supplements.
Stop Supplements If They Aren’t Helping
One of the biggest issues is the continuation of a supplement long after any perceived benefit is gone—or never established in the first place. It’s not uncommon to see patients still taking things like glucosamine, vitamin E, or ginkgo years later simply because “it can’t hurt.” Over time, the pill burden adds up, and so does the cost. Drug interactions are also possible. It’s worth having regular conversations to reassess whether each supplement is still necessary or providing any meaningful effect.
Binding Interactions
Calcium (podcast) and magnesium supplements are frequent culprits of drug interactions. These minerals can bind to certain medications in the GI tract, reducing absorption. Classic examples include antibiotics like fluoroquinolones and tetracyclines, as well as thyroid medications such as levothyroxine. Even iron absorption can be affected when these are taken together. The easy fix? Separate dosing by at least two hours, but many patients aren’t aware of this unless someone points it out.
Companion Medications
When reviewing supplement lists, it’s also important to identify when certain vitamins were started as a “companion” to another medication that’s since been discontinued. For example, vitamin B12 is often added for patients on long-term omeprazole or metformin due to the risk of deficiency from reduced absorption (excellent board exam nugget). However, if either of those medications is later stopped, the ongoing need for B12 supplementation should be reassessed. Similarly, vitamin C is sometimes taken alongside iron to improve absorption, but if the patient no longer requires iron therapy, there’s usually no benefit to continuing vitamin C solely for that purpose. Regularly evaluating the original reason for each supplement can prevent unnecessary use and simplify medication regimens.
Overlapping Ingredients
Patients often take multiple combination supplements without realizing they overlap. For instance, a multivitamin plus a bone health supplement may lead to excessive or unnecessary vitamin D or calcium intake. Similarly, high-dose B-complex products can push levels well beyond what the body needs. These duplications increase the risk for toxicity and side effects, such as constipation, kidney stones, or neuropathy from too much vitamin B6.
What other challenges and patient mistakes with supplements have you seen in your practice?
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