This trial is conducted in Europe. The primary aim of this clinical trial is to locate and compare simulated insulin injections (injections of sterile atmospheric air) in normal weight and obese patients with diabetes mellitus. Injections are done with 6 mm and 12 mm needles with and without lifting of skin fold at different injection sites.

Inclusion Criteria:

• Diabetes mellitus
• Use NovoPen®, NovoPen® 1.5, NovoPen® 3, NovoLet® 1.5 or NovoLet® 3 for at least 3 months
• Body mass index (BMI) for normal weight between 19-25 kg/m2
• Body mass index (BMI) for obese between 25-33 kg/m2

Exclusion Criteria:

• Pregnancy or plans thereof
• Local reactions on injection sites
• Acute, severe infection diseases
• Coagulation disorders