Does taking creatine affects kidnies?

Yes: Yes it can. Should use no more than about 5gm daily.

Creatine.: Creatine in doses of 1000 to 5000mg daily has been shown to increase muscle mass, muscle size and muscle energy stores. Creatine must be taken with lots of water throughout the day, and doses must not exceed 5000mg daily to avoid impairment of kidney function. The dose can be taken all at once, preferably after exercise to facilitate ATP store replenishment in the muscles after exercise.