Humulin® R U-100 is a polypeptide hormone structurally identical to human insulin synthesized through rDNA technology in a special non-disease-producing laboratory strain of Escherichia coli bacteria. Humulin R (insulin human recombinant) U-100 has the empirical formula C257H383N65O77S6 and a molecular weight of 5808.

Humulin R (insulin human recombinant) U-100 is a sterile, clear, aqueous, and colorless solution that contains human insulin (rDNA origin) 100 units/mL, glycerin 16 mg/mL and metacresol 2.5 mg/mL, endogenous zinc (approximately 0.015 mg/100 units) and water for injection. The pH is 7.0 to 7.8.