Figure 1: Structural formula of Novolin R. Novolin R is a sterile, clear, aqueous, and colorless solution that contains human insulin (rDNA origin) 100 units/mL, glycerol 16 mg/mL, metacresol 3 mg/mL, zinc chloride approximately 7 mcg/mL and water for injection. The pH is adjusted to 7.4. Hydrochloric acid 2N or sodium hydroxide 2N may be added to adjust pH.