Can high dose cefelexin (1.5 g/day for a year) cause kidney problems or any other complications/side effects? my dr wants to start me on this for recurrent kidney infections but i just want to better understand the risks first?

This is unusual treatment for recurrent or persistent urinary tract infection, but may be appropriate if your doctor has a good understanding of the nature of the infection and best treatment. It would be appropriate to see an infectious diseases specialist (or in UK, a genitourinary medicine [GUM] physician) if you haven't yet done so. Cephalexin has few side effects, kidney damage unlikely.

It is highly unusual to be on that dose for a year. Any medication taken for a long time can affect the kidneys but it depends on many other factors. You should be investigated thoroughly for cause of recurrent UTI by a Urologist before this course of action is taken. In the meantime drink water, empty your bladder frequently, keep the genital area clean and try some cranberry juice. Wish you well