In this study we compare the vitamin B12 status by measuring serum vitamin B12 and holotranscobalamin in type 2 diabetic patients with and without metformin treatment. Afterwars we investigate which biomarker could be adequate to reflect B12 status in metformin-treated patients.

With the help of a questionnaire we assess clinical, nutritional and demographic factors which are associated with vitamin B12 deficiency.

Inclusion Criteria:

• Diagnosis of T2DM > 6 months
• Metformin treatment for at least 6 months
• Age > 18 years
• Ability to give written informed consent
• No metformin treatment in the last 6 months (control group)

Exclusion Criteria:

• Concurrent intake of preparations containing VB12 (within the last 3 months prior to study participation)
• Lack of written and/or oral understanding in German, French, Italian or English languages
• Diagnosis of Transcobolamin transporter defect
• Diagnosis of Chronic or acute liver diseaseliver insufficiency with CHILD-PUGH scores B and C and acute hepatitis
• Diagnosis of Renal disease (Creatinine-Clearance <60 ml/min)renal insufficiency stadium III, IV and V (KDOQI) and acute renal diseases

Patients with diabetes mellitus type 2 treated with and without Metformin.