Have you ever heard of water pills? Also called diuretics, water pills are medications that help increase the amount of water and salt expelled from the body when you urinate.

There are three types of water pills: thiazide, loop, and potassium-sparing. Thiazide is the most common type of water pill, and is usually prescribed to someone trying to treat their high blood pressure. Thiazide helps to not only decrease fluids in your body, but also relax your blood vessels.

Loop-acting diuretics are used to treat heart failure, and potassium-sparing diuretics are just what they sound like: they allow fluids to exit, but spares any potassium, and doesn’t let that escape. Not surprisingly, these may be prescribed to people with low potassium levels.

Sometimes water pills are also used to treat conditions such as congestive heart failure, which works by reducing fluid buildup that can result from the condition. And in other cases, water pills may be prescribed to women who experience intense bloating while on their period.

As mentioned, water pills are prescribed when you need them. That’s why you should never pick them on a shelf. Some people think that they could relieve bloating or even help them lose weight, but there are many other ways to do that and diuretics should not be used in these cases.

Additionally, any water pills sold over the counter aren’t actually recommended by experts and can be hazardous to your health. These types of water pills have actually yet to be studied in research trials, and could potentially have bad effects especially mixed with any other medications you’re currently taking.

“The problem with OTC meds like these is that you’re not sure exactly what they’re giving you,” says Linda Anegawa, M.D., an internist at Pali Momi Medical Center in Hawaii. “They’re not FDA controlled, so they may not be doing what they claim to and in fact might be making you dehydrated.”

If you take water pills as prescribed, you likely won’t experience any side effects. However, some of the most common side effects can include too little or too much potassium in the blood, low sodium levels, headache and dizziness, diarrhea, excessive thirst, an increase in blood sugar, muscle cramping, a skin rash, and gout.

More rare and serious side effects include kidney failure or an irregular heartbeat. These will likely only occur in those who take over the counter diuretics.

So seriously, don’t go and pick them up if your doctor hasn’t prescribed them. We promise, they may sound cool in theory, but they don’t actually help you lose any weight.

“When you’re weighing yourself, [you’re adding up] bone, fat, muscle and water,” says Lunenfeld. “When you’re looking to lose weight, you’re looking to lose fat and maintain muscle mass. With a diuretic, you’re just losing water weight, which isn’t really getting you any significant weight loss.”

What do you think of water pills? Have you ever heard of them before? Do you know anyone who has been prescribed a diuretic? If so, how did it help them with their symptoms?