The purpose of this study is to assess safety and tolerablility of AZD1656 after multiple repeated oral doses in patients with type 2 diabetes on top of metformin.

Inclusion Criteria:

• Male or female (with non child-bearing potential)
• Diagnosed diabetes Mellitus patients treated with metformin alone or one other anti-diabetic drugs. Stable blood sugar control indicated by no changed treatment within 3 months prior to study start.t
• HbA1c <11 % at screening (HbA1c value according to international DCCT standard)

Exclusion Criteria:

• Clinically significant illness or clinically relevant trauma, as judged by the investigator, within two weeks before the first administration of the IP
• History of ischemic heart disease, stroke, transitorisk ischemic attack or symptomatic peripheral vascular disease
• Clinically significant abnormalities in clinical chemistry, hematology, or urinalysis results.