According to WebMD, green tea does not cause kidney stones but may actually help prevent them. This belief is based on a study done in China, which linked an increased amount of green tea with a flattening of pre-existing kidney stones.
The Mayo Clinic shares that kidney stones form when urine contains more crystal-forming substances than the fluid in urine can dilute. There are many different types of kidney stones, including calcium stones, struvite stones, uric acid stones and cystine stones, as well as other more rare types.
According to the Mayo Clinic, there are some factors that put a person at higher risk for kidney stones. These include not drinking enough water; eating a diet that's high in protein, sodium and sugar; and being obese.