This trial is conducted in Europe. The aim of this clinical trial is to compare the 24-hour pharmacodynamics/ pharmacokinetics of biphasic insulin aspart 30 (BiAsp 30) thrice daily treatment with that of a basal-bolus treatment with insulin glargine and insulin glulisine in type 2 diabetic subjects.

Pharmacodynamics is the glucose-lowering effect of the study medication over the entire observation phase from the time of administration and the efficacy period while the pharmacokinetics is the amount of the study insulin that can be determined in the blood.

Inclusion Criteria:

• Type 2 diabetes mellitus for 12 months or longer
• Body Mass Index (BMI): 25.0-40.0 kg/m2, both inclusive
• HbA1c between 7.0 and 10.5% at screening
• Insulin treatment for at least 3 months prior to screening with a total daily dose of 0.6 and 0.9 U/kg body weight

Exclusion Criteria:

• Use of any oral antidiabetic agent within the past 2 months
• Cardiac disease: NYHA class III or IV chronic heart failure (CHF), unstable angina, and/or any myocardial infarction (treated or untreated) within 6 months prior to screening
• Hepatic insufficiency (alanine aminotransferase (ALT) or aspartate aminotransferase (AST) equal to or greater than 2 times the central laboratory's upper reference limit)
• Renal insufficiency (serum creatinine equal to or greater than 1.6 mg/dL for males; equal to or greater than 1.4 mg/dL for females)
• Recurrent hypoglycaemia
• Anaemia (haemoglobin less than 13.0 mg/dL in males and less than 12.0 mg/dL in females; WHO-criteria)
• Use of concomitant medications (prescribed or non-prescribed and other than insulin) which may alter glucose metabolism including but not limited to: systemic or inhaled glucocorticoids, anabolic steroids, non-selective beta-blockers