When you take a prescription drug in the United States, you can be reasonably sure of what's in it. The Food and Drug Administration (FDA) requires that all pharmaceuticals be thoroughly tested in humans, that they contain whatever ingredients are listed on the label, and that they have evidence to back their marketing claims.

Unfortunately, the same isn't true for dietary supplements.

Americans spend more than $30 billion on supplements each year. Supplements are now the most common form of alternative medicine, and many of these pills promise to do incredible things, from boosting memory and building muscles to burning fat fast.

There's just one problem: These pills are barely regulated. Supplement makers don't need to prove their products are safe or even effective before putting them on store shelves. And while supplements are supposed to be accurately labeled, a Vox review of government databases, court documents, and scientific studies uncovered more than 850 products that contained illegal and/or hidden ingredients — including banned drugs, pharmaceuticals like antidepressants, and other synthetic chemicals that have never been tested on humans.

We found examples of weight loss supplements spiked with cancer-causing drugs that had been pulled from the US market, and brain enhancers laced with chemicals that have never been approved for sale in the US. More than 100 products contained DMAA, a drug that's been banned in the US, UK, and several other countries because it is linked to strokes, heart failure, and sudden death.

In the absence of more stringent regulation, state attorneys general and federal prosecutors have been going after supplement makers and retailers that sell bogus products. Last year, federal researchers released the first estimate on how much damage supplements can do, finding that these pills and potions cause 23,000 emergency department visits nationwide every year, and more than 2,000 hospitalizations.

Were you or someone you know harmed by a dietary supplement? Tell us your story.

Now you can see if your favorite supplement has been flagged by health authorities. We used data from the FDA and the Department of Defense, as well as published studies from scientific journals and court documents, to create a searchable database of dangerous supplements. All of the products listed below have been found to contain hidden drugs.

This database is by no means exhaustive; it only includes products that have been studied or were the subject of safety complaints. Some products in the database may have also been reformulated since they were flagged, and others that are dangerous may never have been tested. Still, it's the most comprehensive look so far at what may lurk in your supplement bottle. As Pieter Cohen, an expert on the supplement industry, warned: "Supplements spiked with dangerous drugs are found in hundreds of stores across America, even in the largest supplement retail chains. Until the law is reformed, tens of thousands of Americans will continue to be harmed by supplements every year."

Below the database, you'll find descriptions of the classes of pharmaceuticals and illegal drugs that have been found in supplements. Many of these ingredients are sold as prescription drugs, which means that patients, at least in theory, have been screened by doctors and are aware of the drugs' potential side effects. When these drugs are illegally added to supplements, consumers don't know they're there and aren't aware of the potential side effects or, importantly, any dangerous interactions with other medicines.

Does this mean your vitamin C is unsafe or that vitamin D doesn't contain what it says on the label? Not necessarily. Representatives from the supplement industry argue it's usually the supplement products that carry big health claims — promising more muscle or faster weight loss — that are the problem. In our database, weight loss products seemed to contain hidden drugs most frequently, followed by sexual enhancement supplements and muscle builders. (This squares with the findings in previous research on supplement safety.)

But the truth is right now you have no way of knowing for sure what's in your supplement bottle.

Does your favorite supplement contain an illegal drug? Search our database to find out.

Last updated January 11, 2016 with additional or revised information.