How do people on prescription diuretics not get dehydrated?



Seems like a lose-lose situation. You take diuretics to lower your blood pressure, but that just makes you pee out all the fluid you drink before your body can absorb it, making you chronically dehydrated and at risk for many other problems. Please explain how this is beneficial.

In: Biology

It depends on the diuretic. You can basically overpower any diuretic by drinking fluids. If you’re taking, say, a thiazide diuretic for high blood pressure, it’s actually not a particularly strong diuretic and the mechanism of long term blood pressure lowering isn’t actually through diuresis (we don’t actually know what the mechanism is). However, if you are taking a diuretic for heart failure or edema (a loop diuretic like Lasix would be used in this case), you actually have excess fluid just sitting on your body. The idea is that you deplete the fluid in your blood vessels and the fluid in the extravascular compartment moves into the blood vessels.

Also of note, diuretics don’t decrease absorption of fluid, they increase excretion. But you are correct in that diuretics can put you at higher risk for dehydration.

I also want to add the fact that your kidneys have auto regulatory mechanisms that prevent excess loss of fluids. If the body’s volume gets to dehydration status then blood pressure raising hormones are released to restore the equiblibrium.

The areas diuretics act on are only minor in the grand scheme of salt and water reabsorption. They act on the fine tuning areas. A hormone called aldosterone acts on another area of the kidneys and can act to counter some of the effects. ACE inhibitors usually block the formation of aldosterone, so those are used to treat blood pressure as well.

Diuretics act (largely) on the kidneys to modify fluid excretion.

Urine is produced from fluid taken from the body, so anything you drink has to be absorbed before you can pee it out.

Diarrhea is fluid that hasn’t been absorbed, just left in the GI tract.