On the basis of reports from a nationally representative sample of emergency departments from 2004 through 2013, we estimated that dietary supplements were implicated in an average of 23,000 emergency department visits and 2000 hospitalizations annually. Although the numbers of emergency department visits and hospitalizations were less than 5% of the numbers that have been reported for pharmaceutical products previously,27 dietary supplements are regulated and marketed under the presumption of safety.

Although the incidence of emergency department visits for adverse drug events is reported to be low among young adults,27 more than one quarter (28%) of emergency department visits for supplement-related adverse events in our study involved young adults between the ages of 20 and 34 years. Weight-loss or energy products caused more than half these visits, commonly for cardiac symptoms (palpitations, chest pain, or tachycardia). Notably, cardiac symptoms were documented more frequently in emergency department visits for adverse events associated with weight loss (43%) and energy products (46%) than for prescription stimulants. In a previous study28 that used the same data source as the one used in our study, cardiac symptoms were documented in 23% of emergency department visits that were associated with prescription stimulants, which have label warnings for sympathomimetic adverse effects. Unlike over-the-counter or prescription medications, there are no requirements to identify adverse effects on dietary-supplement packaging. Clinicians could be encouraged to educate patients about potential cardiac effects from these products. However, since dietary-supplement histories are infrequently obtained,29-32 particularly among young adults,31 other opportunities for informing users of these potential adverse effects may be needed.

Unsupervised ingestions by children caused more than one fifth (21%) of all estimated emergency department visits for supplement-related adverse events, with almost two thirds involving micronutrients. Child-resistant packaging is not required for dietary supplements other than those containing iron,33 and despite such packaging, iron supplements were the second most commonly implicated type of supplement in unsupervised ingestion by children. Innovative safety packaging and targeted education on safe storage are potential interventions to reduce unsupervised ingestion of supplements by children.34

Among older adults, swallowing problems caused nearly 40% of emergency department visits for supplement-related adverse events, with micronutrients implicated in more than 80% of these visits. The FDA recommends limiting the size of pharmaceutical tablets to 22 mm and requires the reporting of tablet size and shape on abbreviated new-drug applications.35 However, there are no size recommendations or similar reporting requirements for dietary supplements. Large amounts or multiple types of micronutrients are often packaged in a single large pill, and many micronutrient products approaching or exceeding 22 mm are commercially available.36 Considerations for reducing the number of emergency department visits for swallowing problems include decreasing the size of supplement pills or using other delivery vehicles (e.g., liquids, gels, or powders), particularly for micronutrients for older adults, along with educating patients on methods for avoiding swallowing problems.

Limitations of our analysis should be noted. The number of emergency department visits attributed to supplement-related adverse events that we identified is probably an underestimation, since supplement use is underreported by patients, and physicians may not identify adverse events associated with supplements as often as they do those associated with pharmaceuticals.29-31,37 Physicians also may have more limited knowledge of interactions between prescription drugs and dietary supplements than they do interactions between prescription drugs. In addition, we did not collect data on emergency department visits associated with products that are generally considered to be foods or drinks by consumers but that may be considered to be dietary supplements under the Dietary Supplement Health and Education Act (e.g., energy drinks). However, it is also possible that emergency department physicians may incorrectly attribute certain symptoms to supplements, which could lead to overestimation.

The relatively wide confidence intervals around the reported national estimates indicate the precision limitations of using a relatively small, albeit representative, sample of hospitals. Sample size and design also prevent identification of differences among metropolitan areas, states, or regions. Nonetheless, population-based active surveillance can quantify adverse events better than voluntary reporting.10

A limited regulatory framework makes it challenging to accurately monitor the safety of supplements.18 It was not possible to calculate rates of emergency department visits for adverse events associated with supplements according to specific ingredient, product, or type, because data quantifying supplement use are extremely limited. Estimates of overall supplement use are available from national surveys, but studies have used varying categorizations, and most lack product-specific data.5,38 Identifying specific ingredients is also challenging because dietary supplements often contain multiple ingredients, and similarly named products can have different ingredients. For example, a product called Pro Clinical Hydroxycut Lose Weight lists 10 active ingredients, none of which are the three listed active ingredients in Hydroxycut Appetite Control.39

We categorized supplements on the basis of common reasons for use. In some cases, products were identified only by intended use (e.g., weight-lifting supplement). In other cases, specific products or ingredients were named, but because some products and ingredients are marketed for multiple uses (e.g., to improve energy and sexual performance), patients’ reasons for use might have differed from assigned categories.

In conclusion, we estimate that more than 23,000 emergency department visits annually in the United States from 2004 through 2013 were for adverse events associated with dietary supplements. Such visits commonly involved cardiovascular adverse effects from weight-loss or energy herbal products among young adults, unsupervised ingestion of micronutrients by children, and swallowing problems associated with micronutrients among older adults. These findings can help target interventions to reduce the risk of adverse events associated with the use of dietary supplements.