I Am A Type I Diabetic. I Am Taking Zithromycin

I am a Type I diabetic. I am taking zithromycin for a sinus infection, and was advised to use fluticasone propionate nasal spray daily. Shortly after using it, however, my blood sugar rose to 250. I am a careful eater, so I'm ruling out eating as the culprit at this time. Is the nasal spray the cause of this sudden rise, or could it be the sinus infection, or the antibiotic?