Does diovan (valsartan) hctz affect kidney function>?

YES: Diovan hctz (hydrochlorothiazide) (blood pressure med) which is now available generically is a combination of a diuretic (water pill) which does increase "kidney function" and a drug valsartan which is an arb. Arbs also work in the kidney to help control blood pressure by "telling" the kidneys not to retain fluid (and potassium) in response to a lower blood pressure. This has a protective effect for diabetic kidney.

Yes: As long as the kidney function is normal it protects it!