While supplements contain ingredients that are found in foods, there are potential safety concerns to consider before taking concentrated amounts of these ingredients in supplement form.

Possible interactions

In addition to talking to your healthcare provider about the type of supplement you’re interested in taking, it’s critical to ask about any potential interactions.

The ingredients in supplements, including vitamins, minerals, herbs, and other botanicals, can have unintended negative consequences when combined with some medications, other supplements, foods, and alcohol (27).

For example, vitamin E supplements may increase the risk of bleeding in those on blood-thinning medications, while calcium supplements may limit the effectiveness of antibiotics and reduce the absorption of iron from foods and supplements (28, 29).

Some supplements may also affect the accuracy of lab results.

For example, the FDA issued a warning that supplements containing biotin (vitamin B7) can falsely lower troponin-based lab results, an important biomarker that’s used to help diagnose heart attacks (30).

Supplements containing herbs and botanicals can be particularly concerning, as many have been shown to interact with various medications. Additionally, many herbs have insufficient research in humans to confirm potential interactions and side effects (31, 32).

Ingredients that may become toxic over time or at high doses

One concern with consuming vitamins and minerals through supplements rather than from foods is the increased risk of consuming an amount that’s too high or could become toxic over time.

In addition to recommended amounts, many vitamins and minerals have what’s called a Tolerable Upper Intake Level (UL). The UL is the highest intake amount of the nutrient that’s unlikely to cause negative side effects in the general population (33).

The UL for vitamins and minerals varies based on age and gender. There are also separate UL recommendations for women who are pregnant or breastfeeding (34, 35).

Fat-soluble vitamins are particularly concerning in regards to toxicity risk, as excessive amounts can accumulate and be stored in your body.

In particular, overconsuming vitamins A, D, and E can be toxic, leading to side effects like irregular heartbeat, organ damage, hemorrhages, hemorrhagic stroke, and in extreme cases, even coma and death (36, 37, 38, 39).

As water-soluble vitamins are not stored in your body, they’re less likely to cause toxicity from an overdose.

That said, consistently taking very large doses of water-soluble vitamins may still cause digestive upset, liver damage, and even potentially irreversible neurological damage (36, 40, 41).

Unless under the supervision of a medical professional, it’s important not to exceed the UL of vitamins or minerals. While some side effects may be mild, others can be more serious.

Additionally, as the UL for kids is often much lower than for adults, kids are particularly at an increased risk of overdose and toxicity (34).

For safety purposes, make sure to always store supplements out of reach of children. This is especially important for gummy vitamins, as their sweet flavor may appeal to kids (42, 43).

May have negative side effects

Dietary supplements may cause negative side effects, even when taken at the recommended doses.

Reported side effects are often mild, such as nausea, diarrhea, or headaches. In particular, iron supplements are known for causing digestive distress (44).

However, some ingredients in supplements, especially herbs, may have more serious side effects, such as allergic reactions, increased blood pressure, and elevated or irregular heartbeat (45, 46).

May not be effective

As dietary supplements are subject to fairly limited regulation, there’s also the risk that the product contains less of an ingredient than it claims to.

In addition to not getting your money’s worth, this can be potentially dangerous in individuals who are relying on the supplement to help meet their essential nutrient needs.

It’s also important to be cautious of claims on the product. Due to FDA regulations, manufacturers cannot claim that their product cures, treats, or reduces the risk of a specific disease or condition unless it has been proven by research to do so (47).

However, they can include structural or functional claims, which describe how the ingredients in the product may affect systems or organs in your body (47).

For example, a supplement can say that it supports energy levels. Yet, this claim does not require that the product was scientifically proven to help improve energy levels. As a result, there’s no guarantee that taking the supplement will result in this desired benefit.

Summary

Taking supplements carries some risks. Depending on the type and level of ingredients, there are risks of side effects, toxicity, and interactions with drugs, foods, and alcohol. Additionally, supplements are not guaranteed to be effective.