Also known as water pills, diuretics are medications recommended to treat a number of conditions where your body’s ability to regulate water is affected, such as kidney disease. Different types of diuretics exist, but one type -- known as a loop diuretic -- affects how the kidneys regulate water in the body, encouraging the release of built-up water in the body.

How the Kidneys Work

Your kidneys are the filters of your body and maintain the delicate fluid balance. Because your body is about three-quarters water, having the right fluid amounts is important. Too much fluid increases your blood pressure and not enough can dry out blood and skin cells, causing dehydration. The kidneys regulate water through a system known as the renin-angiotensin-aldosterone system. When the kidneys sense too much water in the body, they signal the release of these hormones, which encourage you to urinate to get rid of excess water. When you don’t have enough water, the kidneys retain these hormones, making you hold on to more water in your body.

Sodium and Your Kidneys

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Your kidneys use sodium as a means to retain water in the body. Sodium and water are naturally attracted to each other. Because sodium is the major ion outside your cells, extra salt outside your cells causes your body to retain water -- this is why you tend to become bloated after a salty meal. If your kidneys sense you do not have enough water in your body, they will take in more sodium through the foods and drinks you consume, which then increases your fluid levels in the body. Loop diuretics directly affect this process in the kidneys by signaling the body not to absorb sodium.

Specific Process

When you take a diuretic, the medication moves to the kidneys. Inside the kidneys are small loops known as the loops of Henle that regulate sodium intake. The medication signals the calcium/potassium pump in the kidneys to stop taking in sodium. However, this flushes out minerals like calcium, potassium and magnesium, which is why potassium loss can be a side effect of taking a loop diuretic. The sodium that is released attracts water in the body, causing your body to release it.

When They’re Prescribed

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Loop diuretics for the kidneys are prescribed for a number of medical conditions. If you are experiencing kidney failure, diuretics can help make up for lost kidney function. They also are prescribed when patients are experiencing edema -- a condition that causes water retention. If you have excess potassium in your blood, a physician may prescribe a diuretic. Remember that diuretics can have toxic effects when they are taken without a physician’s advice. Always talk to your doctor before taking a diuretic.