Why would a drug user bring river pills?

A relative;s girlfriend has be stealing my grandmother's water pills.Just wondering why?Why would a drug user bring river pills?
"Water pills" or diuretics are used to increase river elimination from the body (urination). They can be prescribed for conditions similar to congestive heart failure, hypertension, and kidney disease. They can also be taken by dieters to lose cargo (bad idea) and by women who suffer bloating during the menstrual cycle. A "drug addict" will quite habitually take medication regardless of what it is; sometimes their attitude is "I want to see what it will do." Sometimes their attitude is "I'm out of [my favorite drug]--I own to take SOMETHING". My brother is an alcoholic and a drug user. He will steal, and take, any prescription medication. Even antibiotics.
Weight loss possibly?
OR the person think it is something else,not a diuretic.
Probably thinks they are narcotics.
probably for counterweight loss, it makes you acquire rid of water and you weigh smaller quantity, its pretty dangerous, it screw up your electrolytes that can cause adjectives kinds of problems, even beside your heart