This trial intends to investigate the pharmacodynamics, pharmacokinetics, safety, and tolerability of insulin GZR33 (hereafter referred to as GZR33) and estimate its potency in comparison with insulin degludec.

Inclusion Criteria: type 1 diabetes for at least 12 months

• 18-64 years of age
• HbA1c <= 9.0%.
• Body Mass Index (BMI) between 18.5 and 29.0 kg/m^2
• treated with a stable insulin regimen for at least 2 months, in a dose > 0.2 and < 1.2 U/kg/day

Exclusion Criteria:

• blood pressure outside the range 90 to 140 mmHg (systolic) or 50 to 99 mmHg (diastolic)
• clinically significant concomitant diseases
• recurrent severe hypoglycemia (more than 1 severe hypoglycemic episode requiring assistance from another person within 180 days before screening)
• hypoglycemia unawareness
• estimated glomerular filtration rate (eGFR) <60.0 mL/min/1.73 m2