What does tonic water do to your body?

Answer 1

Quinine, the additive in tonic water, causes side effects within the body that is dangerous in large amounts. Known effects on the body reported are rare blood disorders, stomach cramps, vomiting, and diarrhea.

Answer 2

Some manufacturers also produce diet (or slimline) tonic water, which may contain artificial sweeteners.

Because of quinine's risks, the United States Food and Drug Administration has declared that nonprescription sources, such as tonic water, should not be used to prevent or treat leg cramps.

In the United States, the Food and Drug Administration limits the quinine content in tonic water to 83 ppm (83 mg per litre if calculated by mass), while the daily therapeutic dose of quinine is in the range of 167-333 mg. Still, it is often recommended as a relief for cramps, but medical research suggests some care is needed in monitoring doses.