5 Types of Supplements You Should Always Skip, According to Experts

Over the shoulder view of young woman browsing through supplements and reading the label on a bottle of supplements in front of the shelves in a pharmacy


You can find aisles and aisles of supplements at your local supermarket or drugstore. They sit on the shelves unassumingly, advertising naturally-derived ingredients that can do everything from helping your hair grow to improving your eyesight. To purchase one, all you need to do is pick one up—no prescription necessary. 

Though they may seem harmless, many supplements contain potent ingredients. Some can interact with medications, cause unwanted side effects, and potentially harm your health. And while some products may simply be ineffective, others can be downright dangerous. Most importantly, supplements are not regulated by the U.S. Food and Drug Administration.

Remember, supplement trends fluctuate—though some have historically been more popular than others. Regardless of the latest fad, you should take all supplements cautiously. There are even a few you should skip altogether. To help you determine which supplements to avoid, we asked experts to weigh in. 

The Food and Drug Administration (FDA) doesn’t test supplements for effectiveness, potency, or purity. Therefore, it’s left to the manufacturers to ensure that their products are safe and beneficial to human health. 

Weight Loss Supplements

Weight loss supplements, also known as diet pills, have been touted as supplements that can help an individual lose weight. Often, they promise to boost your metabolism, curb your cravings, act as a meal replacement, prevent your body from absorbing the foods you eat, or decrease fat production. 

They come in pills, shakes, teas, and powders and often have mixed ingredients like various herbs, minerals, fiber, and vitamins. While some of these ingredients may not be harmful, they could be ineffective, or worse, produce scary side effects. 

One such ingredient is ephedra, which was banned by the U.S. Food and Drug Administration (FDA). They discovered that the substance could cause vomiting, nausea, mood shifts, anxiety, stroke, seizure, abnormal heartbeat, heart attack, and even death.

Even though diet pills can no longer legally contain ephedra, they contain other common ingredients that have not been studied enough to understand how they react with other supplements and medications.

For example, if taken in large quantities, green tea extract can cause abdominal pain and liver damage. The U.S. Pharmacopeia or USP, a commonly seen name and symbol found on supplements, indicates that green tea extract should not be taken on an empty stomach nor should it be taken if you have a liver problem. They also advise discontinuing use and consulting a healthcare provider if you develop symptoms of liver trouble such as abdominal pain, dark urine, or jaundice.

"A potentially dangerous ingredient in weight loss pills is chitosan, which is a fat binder," says Molly Morgan, RD, a registered dietitian at Creative Nutrition Solutions. "In theory, it interferes with fat absorption and also then interferes with absorption of fat-soluble vitamins A, D, E, and K, which play key roles in the body."

Supplements With Sexual Enhancement Claims

Another supplement that started trending around the same time as weight loss remedies were agents promising sexual enhancement. Many claim to help with erectile dysfunction (ED), though others market that they can increase stamina and even physical size. 

Even FDA-approved sexual enhancement medications, like Viagra, can come with side effects, including headache, flushing, and indigestion. But when supplements use counterfeit phosphodiesterase-5 inhibitors—the primary ingredient of Viagra—the side effects become much more dangerous. For instance, the compound can interact with other medications, causing mild to severe hypotension.

Jenna Volpe, RDN, LD, CLT

According to a 2022 FDA medical fraud investigation, certain sexual enhancement supplements were found to contain potentially toxic, harmful ingredients that were not listed on labels and, in some cases, found in prescription drugs.

— Jenna Volpe, RDN, LD, CLT

Counterfeit sexual enhancement supplements are particularly dangerous. The FDA warns that they can be tainted with contaminants harmful to human health. In addition, these ingredients are often used as bulking agents and may not appear on the product label. If tainted, these supplements can do more harm than good.

"According to a 2022 FDA medical fraud investigation, certain sexual enhancement supplements were found to contain potentially toxic, harmful ingredients that were not listed on labels and, in some cases, found in prescription drugs," says Jenna Volpe, RDN, LD, CLT a registered dietitian with Whole-istic Living, LLC. "This is a huge concern because not only are these supplements altering biochemistry, but they're putting people at risk of cardiac complications and/or liver toxicity,"

Exercise and Sports Performance Supplements 

If you’ve watched television, scrolled social media, or have been to a sporting event, you’ve likely encountered an advertisement for an exercise or sports performance supplement. They come in various forms, such as bars, drinks, capsules, and powders. Each one promises multiple benefits, from increased energy to greater muscle mass. Their retail sales can total $5.67 billion or more each year.

Many of these products designed to help hydrate and fuel athletes contain protein, carbohydrates, amino acids, vitamins, and minerals that aren’t innately harmful. But using too many supplements simultaneously, can cause health concerns.

There also are many banned substances for use by professional athletes. The World Anti-Doping Agency maintains a list of all the drugs prohibited for athletes, with the most abused being methylhexanamine (DMAA). This compound is a stimulant that can help increase energy.

Interestingly, DMAA is also a vasoconstrictor, which is why it appears in over-the-counter congestion medications. But it is dangerous because it has the potential for addiction and abuse and can produce side effects like a rapid heartbeat.

Molly Morgan, RD

Probably the biggest risk to athletes is the lack of regulation around supplements; you think you are taking one product, when in actuality you could be taking that product, plus hidden ingredients. Besides a potential health risk, it could result in a negative drug test result for a banned substance.

— Molly Morgan, RD

"Probably the biggest risk to athletes is the lack of regulation around supplements, you think you are taking one product, when in actuality you could be taking that product, plus hidden ingredients," says Morgan. "Besides a potential health risk, it could result in a negative drug test result for a banned substance."

The risk of suffering severe and even fatal harm from sports performance supplements leads experts to advise that you steer clear. If you still want to use dietary supplements to support athletic performance or exercise, look for the NSF Certified for Sport label. 

This designation is given to products reviewed for contaminants, masking agents, and prohibited substances by the only third party (the National Sanitation Foundation) certified by the United States Anti-Doping Agency.

Supplements With Unsupported Claims 

Along with the supplements mentioned above, an entire host of health and wellness products make claims not supported by clinical research. Although the FDA does not regulate dietary supplements, they can pull products that make false claims and those that are misbranded. 

Unlike drugs, the FDA does not require clinical trials or testing of a supplement's safety before it can be sold to consumers. Instead, manufacturers must provide evidence of their products' effectiveness. 

Health claims describe how a supplement can reduce the risk of a specific medical condition. Structure or function claims tell consumers how an ingredient relates positively to a structure or function of the human body.

For example, calcium supports bone health. Supplements can only make these claims if they have evidence to support it and include an FDA disclaimer. Unfortunately, some supplements may not comply with these rules.

The FDA will eventually pull their products, but it doesn’t happen overnight. Be cautious when choosing supplements that don’t have evidence supporting their claims, make statements that seem too good to be true, or have a history of noncompliance. 

"What’s really important to know about any supplement is that if some is good, more is not better," says Morgan. "For example, if the recommended dose is two capsules per day, taking more could have negative side effects and be a detriment to your health."

Potentially Harmful Supplements

Just because a product is on the shelf doesn’t mean that it is proven to be safe and effective. Stores can sell various supplements that may possess harmful qualities. For example, caffeine pills are considered safe for most individuals as long as they take them in moderation and limit other sources of caffeine while under the influence of the pills.

However, some individuals should not take caffeine pills, such as those with high blood pressure. There also are no studies investigating their interaction with other medications. If you take too much, you may experience a number of adverse side effects.

Katie Tomaschko Tout, MS, RDN, CDN

Caffeine pills can be harmful due to caffeine's stimulatory effects. They may cause anxiety, insomnia, increased heart rate, and blood pressure. This is all very individual dependent.

— Katie Tomaschko Tout, MS, RDN, CDN

"Caffeine pills can also be harmful due to caffeine's stimulatory effects," says Katie Tomaschko Tout, MS, RDN, CDN, a registered dietitian. "They may cause anxiety, insomnia, increased heart rate and blood pressure. This is all very individual dependent."

Even popular supplements thought to be safe, such as calcium, can be problematic if combined with other drugs and supplements or taken too high a dose. For example, a combined intake of calcium and Vitamin D could lead to a higher risk of a stroke.

"Supplements containing very high amounts of vitamins and minerals—such as iron, zinc, and vitamins A, D, E and K—can also be harmful," says Tomaschko Tout. "They can reach dangerous toxicity levels in the body if over consumed."

Other harmful supplements you could take improperly include fish oil, kava, St. John’s Wort, and soy isolate. More research is needed on the safety and efficacy of these and other supplements. 

A Word From Verywell

Use the buyer-beware approach when choosing supplements. Because they are not required to undergo clinical trials or testing to prove their safety and effectiveness, many supplements can pose a risk. This is especially true if you take them improperly, use them in combination with other drugs or supplements, or attempt to manage an underlying health condition.

If you are considering adding any supplement to your diet, consult a healthcare professional first. They can advise you on the safety, quantity, and impact—particularly if it might interact with other supplements or medications you are taking. And, if you believe you have overdosed on vitamins or supplements, or are experiencing an adverse reaction, seek immediate medical attention.

17 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Nicole M. LaMarco
Nicole M. LaMarco has 19 years of experience freelance writing for various publications. She researches and reads the latest peer-reviewed scientific studies and interviews subject matter experts. Her goal is to present that data to readers in an interesting and easy-to-understand way so they can make informed decisions about their health.