The purpose of the study is to compare the human insulin inhalation powder plus oral anti-hyperglycemic medication with injected insulin (neutral protamine hegedom insulin) plus oral anti-hyperglycemic medication on lowering the blood sugar level.

Inclusion Criteria:

1. Type 2 diabetes mellitus for at least 6 months
2. One or more oral antihyperglycemic medications for at least 12 weeks
3. HbA1c equal to or greater than 7.0%, and equal to or less than 10.5%
4. Nonsmokers, have not smoked for at least 6 months and agree not to smoke (cigars, cigarettes, or pipes) or use smokeless tobacco for the duration of the study
5. Satisfactory lung function results to meet the requirement of the study

Exclusion Criteria:

1. Previously received any form of inhaled insulin
2. Have a current diagnosis or past history of asthma, chronic obstructive pulmonary disease or other clinically relevant lung disease
3. History or presence of liver disease
4. History or presence of kidney disease