Tainted supplements: which products the FDA has found to contain hidden drugs, and what was in them

The pills sold at gas station counters under names like Rhino and Magnum were the subject of an article in The Conversation on October 13. Its author, Andrew Yockey, a public health researcher at the University of Illinois Urbana-Champaign, pointed out that the problem is current: in September 2026, seven new products were added to the list that the US Food and Drug Administration (FDA) keeps of supplements caught with hidden drugs.

That list has been growing since 2007, and every entry is a product sold as a dietary supplement that turned out, when tested, to contain a real drug. A published count of its first ten years found the same three kinds of product again and again, often laced with medicines that had been pulled from the market, and found that fewer than half were recalled. This explainer covers what a tainted supplement is, which products have been caught, what was in them and what the list cannot show.

What a tainted supplement is

A dietary supplement, in US law, is a product such as a vitamin, mineral, herb or amino acid that is not meant to treat or prevent disease. More than half of American adults report taking one.

A tainted supplement is one that contains a pharmaceutical drug. Pieter Cohen, writing in JAMA Network Open, calls this pharmaceutical adulteration: an active drug is included in a supplement that claims to be botanical, as with sildenafil in a “natural” sexual enhancement product.

This can happen because of how supplements are regulated. A 1994 law treats them as a category of food, so, as Yockey writes, they generally do not go through the FDA’s approval process before going on sale. A prescription drug has to be shown to be safe and effective first, and a supplement does not.

The FDA’s work starts after products are on sale. Cohen notes that the agency does not assess the safety of supplements before they reach the market, but that it is tasked with finding and removing adulterated and hazardous supplements once they are there. It does this by inspecting factories, screening imports, following up complaints and testing a sample of products, but, Yockey notes, it does not routinely test every supplement on the shelves. When the FDA finds a hidden drug, it posts a warning and adds the product to a public database.

Which supplements the FDA has found to be tainted

In 2018, five researchers published an analysis of that database in JAMA Network Open, a peer-reviewed medical journal. Reading every warning from 2007 through 2016 and removing duplicates, they counted 776 adulterated dietary supplements identified by the FDA.

Nearly all of them fell into three groups: 353 (45.5%) were marketed for sexual enhancement, 317 (40.9%) for weight loss and 92 (11.9%) for muscle building. The remaining 14 were sold for other purposes, mainly joint and muscle pain.

In almost every case the drug was a secret, and 757 of the 776 products, or 97.6%, did not declare it on the label. One product in five, 157 in all (20.2%), contained more than 1 unapproved ingredient, including 33 with three or more and two with six.

The FDA still describes the same pattern on its warning pages, which say such products are usually sold for weight loss, sexual enhancement, pain relief and body building, often with the claim that they are all natural.

What hidden drugs were in the tainted supplements

Each category had a signature drug. Sildenafil turned up most often in sexual enhancement supplements (166 of 353, or 47.0%), sibutramine in weight loss supplements (269 of 317, or 84.9%), and synthetic steroids or steroid-like ingredients in muscle building supplements (82 of 92, or 89.1%).

Sexual enhancement. Sildenafil is the active ingredient in the prescription drug Viagra. Another 134 products, or 38.0%, contained an analogue of it, a compound with a slightly altered chemical structure that acts in a similar way and has not been through approval. Tadalafil, the active ingredient in Cialis, was in 72 products, and fourteen contained dapoxetine, an antidepressant that the FDA has not approved.

Analogues keep multiplying. Sildenafil and tadalafil belong to a drug class called phosphodiesterase type 5 inhibitors, and a 2023 review cataloged 112 unapproved members of that class found in sexual enhancement dietary supplements and other products between 2003 and July 2023. Two-thirds were variations on sildenafil.

Weight loss. Sibutramine, which was in 269 of the 317 tainted weight loss products, was removed from the US market in 2010 because of risks to the heart and blood vessels. Phenolphthalein, a laxative removed from US over-the-counter products in 1999, was in 75, and fluoxetine, a prescription antidepressant, was in 17. Two contained ephedrine, a stimulant banned from supplements in 2004, and they were found six and eight years after the ban.

Muscle building. Anabolic steroids, synthetic relatives of testosterone, or steroid-like substances were in 82 of the 92 products. Nearly all of these were identified in 2009 and 2010, and 66 were named in a single recall.

Pain. Of the 14 other products, half contained diclofenac, a prescription anti-inflammatory painkiller, and five contained dexamethasone, a steroid used for inflammation.

Why hidden drugs in supplements are a risk

The drugs involved are real medicines with real effects, taken by people who do not know they are taking them. The 2018 authors see harm arising through accidental misuse, overuse, or interactions with other medicines, with a person’s existing health conditions or with other drugs in the same supplement.

The clearest example is one the FDA repeats in its notices on sexual enhancement products. Sildenafil and tadalafil can react with nitrates, medicines that widen blood vessels and include nitroglycerin, and together they may lower blood pressure to dangerous levels. Nitrates are commonly taken, the agency notes, by people with heart disease, diabetes, high blood pressure or high cholesterol.

The authors of the 2018 paper point out who that puts at risk. Men on nitrates are told not to take drugs like Viagra, and some may turn to a supplement labeled all natural for that very reason, unaware of what it contains. Do not stop or change a prescribed medicine without talking to your doctor.

Sibutramine works the other way: the paper warns that it can substantially raise blood pressure or pulse in some patients, a danger to people with a history of heart disease or stroke. Six weight loss products contained both sibutramine and sildenafil.

Dose is a further unknown, because, as the paper notes, the drugs are present at unknown concentrations. A recent FDA notice shows what that can mean. Laboratory tests found yohimbine, tadalafil and flibanserin in a product called WAP Sensual Enhancement, none of them listed on the product label. Flibanserin is the active ingredient in a prescription drug for low sexual desire in women, and yohimbine is a plant-derived chemical that was once used in a prescription medicine for erectile dysfunction. The FDA said the product held dangerously high levels of yohimbine, enough to cause severe high blood pressure, irregular heartbeat and heart attack.

How often tainted products injure people is not known. A study in the New England Journal of Medicine looked at supplements in general and attributed an estimated 23,000 emergency department visits a year in the United States to their harmful effects. Weight loss and energy products accounted for most of the visits involving chest pain or a racing heart. That study counted visits attributed to supplements of all kinds, and it does not say how many involved a hidden drug.

What happened after the FDA warned about tainted supplements

A warning did not always end a product’s life. The 2018 analysis found 28 products named in 2 or 3 warnings issued more than 6 months apart, and 19 of them had a different hidden drug the second or third time.

Yockey describes the same thing from the seller’s side: products can disappear and reappear under new names, and makers can swap one chemical for another. The article cites a study that followed one sexual enhancement product from 2007 through 2022 and found drugs from the sildenafil and tadalafil class in every version they tested. The particular compound changed over time, and the product was still on sale at the end.

Recalls covered a minority. Of the 776 products, 360, or 46.4%, were the subject of a voluntary recall by the company, while another 342, or 44.1%, drew only a public notification, a posted warning to consumers. The paper also recorded news releases, consumer updates and warning letters to firms. Over the decade the balance shifted toward public notifications, and from 2012 to 2016, 72.5% of tainted products were dealt with that way.

Often there was no company to pursue: for products reported from 2012 to 2016, no firm was identified in 69.1% of cases. Many of the samples had not come from American shops at all. In the last three years of the data, 117 of 303 adulterated samples (38.6%) were found through online sampling, and 104 (34.3%) through the examination of international mail.

Cohen’s commentary, published in the same journal on the same day as the analysis, was titled “The FDA and Adulterated Supplements: Dereliction of Duty.”

Tainted supplements since 2016

The pattern has continued. A 2022 update by C. Michael White extended the count by five years, to 1068 unique products found to be adulterated from 2007 through 2021, with sexual enhancement and weight loss products still in the lead. Muscle building was the exception: since 2017, White reported, no additional adulterated products have been identified in that category.

The forms have changed more than the contents, with recent warnings covering pills, gummies, honey, coffee and chocolates, according to The Conversation. On honey alone, an FDA page current as of April 22, 2026, reports that four companies received warning letters for illegally selling tainted honey-based products, and that notifications went out on 24 products.

Other ingredients have also turned up. In 2023 the FDA found sildenafil and acetaminophen, the painkiller in Tylenol, in a Rhino-branded product, and neither drug appeared on its label. Yockey points out that someone also using a cold medicine could unknowingly exceed recommended amounts of acetaminophen.

What the tainted supplements list cannot show

How common tainted products are. The database records what the FDA tested and caught. The 2018 authors acknowledge that the total number and variety of products the FDA tests each year is unknown, so a rise or fall in the count could reflect the agency’s priorities as much as the market.

Products never tested. The FDA says as much of its own list, stating that it is unable to test and identify all products sold as dietary supplements that carry potentially harmful hidden ingredients.

Drugs nobody looked for. The results cover only the drugs for which the FDA tested, so a new analogue that no test targets would not appear.

Shops against websites. Because sampling concentrated on online sellers and imports, the analysis does not show how often tainted products sit on the shelves of ordinary stores.

Harm. The database is a record of ingredients. It does not track who took the products or what happened to them.

Recalled without a test. The authors say a few of the recalled products may have been named without being tested, because firms sometimes recall all of their products as a precaution after one comes under scrutiny. The count of 776 includes them.

Independence. The authors state that the analysis was performed independent of any FDA involvement.

Whether a supplement is safe alongside a particular person’s medicines or health conditions is assessed by their doctor.

Nearly two decades of FDA testing show that the supplements the agency has most often caught with a hidden drug are the ones that promise a drug-like effect.