My Doctor Just Prescribed Losartan Potassium 25mg, 1/2 Tab Per

My doctor just prescribed Losartan potassium 25mg, 1/2 tab per day. When I questioned him about why this medication he said it was preventative to help my kidneys. I am still not convinced about this since I don't have any kidney issues GFR @69, creantine @1.2. I've read about the uses and side effects I don't seem to meet any of that criteria but he's been my endo. for over 19 years. Help