Niaspan only increases blood at doses above 2000 mg a day. And this is an issue that really should only be of concern to diabetics.
I've been taking 3000 mg Niaspan for about 1.5 years now, and my blood sugar sometimes is barely higher and sometimes not.
You should be fine on 2000 mg Niaspan a day.
But one last question: Why are you upping your dose when you Tot-C is only 100 and your LDL on a paltry 20? Is you Doctor obsessed? I'm hoping you have other heart aliments your Doctor is concerned with.
Best of luck!