Dear, author 

I used 100 mg/kg body, ip. for induction of diabetes and oxidative stress  in rats several times, so you can used 25 mg/rat (200-250 gm body weight) dissolved in half ml of phosphate buffer pH 7.4. 

with best of luck and success

25 mg/rat (200-250 gm body weight) dissolved in half ml of phosphate buffer pH 7.4.

Dear Dr. Al-Diwan,

as our experience shows the diabetogenic dose of alloxan  depends on rats strain and other factors so it may be expedient to choose the proper (for your conditions) dose previously. We generally use the doses higher than mentioned above  - in the range of 120-150 mg/kg s.c. single admininstration (dissolved in a phosphate buffer) with the subsequent selection of rats with glycemia higher than 10 mmol/l

Best regards