Any tonic water, diet or otherwise, that contains quinine water can cause permanent kidney damage and both internal and external bleeding, according to LiveScience. These effects motivated the Food and Drug Administration to prohibit the prescription of quinine for leg cramping in 2010.
As of 2015, quinine is still a treatment for malaria, although because of the potential side effects, doctors only use it when newer drugs do not fight the disease, reports LiveScience. Quinine can cause bleeding through thrombocytopenia, or a reduction in platelet count. As many as 4 percent of patients who take quinine in medicinal doses end up with thrombocytopenia or kidney damage.
The amounts of quinine in a glass of tonic water does not trigger these problems in the majority of people; when it does occur, it is known as a gin and tonic purpura, as stated by LiveScience. Some people develop allergies to quinine from drinking tonic water occasionally, but the reaction does not occur until they take quinine in larger doses later in life, threatening their health.