ELI5, what are water pills and why are they prescribed as opposed to simply advising patients to drink more water?

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ELI5, what are water pills and why are they prescribed as opposed to simply advising patients to drink more water?

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Water Pills are medications that increase kidney function and aid the body in losing water. They are extreme diuretics. They are used when people have or are at risk of heart failure and are retaining fluid that they should not be retaining.

Diuretics help rid the body of sodium which reduces high blood pressure. Just drinking water doesn’t help the kidneys to release sodium the way a diuretic aka water pills do.

There are several different kinds of “water pill” and they’re given for a bunch of very interesting, but not ELI5, reasons, but here are two that are.

Lighter water pills are given for high blood pressure, usually as an addition to some other blood pressure medicine. This is also helpful when someone’s kidneys don’t work as well as they used to.

Stronger water pills are given when there are medical problems interfering with the normal water balance of the body. A very common one is congestive heart failure (CHF). To understand why a strong water pill like Lasix is required for CHF, you have to understand the root problem of CHF.

1. The heart, for any of a large number of reasons, is failing as a pump (heart failure), which means blood/plasma back up in the system (“congestion”).
2. Failing as a pump leads to decreased blood flow going forward.
3. The kidneys detect decreased blood flow and interpret that as dehydration, so they flip on the “retain water” switches.
4. Retained water increases blood volume.
5. Increased blood volume puts more strain on the heart, causing it to fail worse.

This cycle repeats over and over again, and is a downward spiral. This progressive failure of the heart is what leads to death in CHF patients. Even if you drank very little, there’s still water in food and the kidneys will retain it because they falsely think you’re dehydrated. Enter Lasix.

Lasix works on step 3 in the above cycle. It artificially keeps a very strong “retain water” switch in the kidneys off, so urine is still made and blood volume is kept under relative control.