This is the investigatory study to find out metformin's pharmacokinetics, pharmacodynamics and drug-drug interactions classifying the group by MATE1 genotype in healthy volunteers. The investigators will apply ranitidine and verapamil to the drug interaction study of metformin.

Inclusion Criteria:

• Healthy male volunteers aged 20 to 50 years at screening
• Subjects whose weights are heavier than or equal to 50 kg and ±20% of ideal body weight : Ideal body weight = (height cm - 100) x 0.9
• Subjects who provided written, voluntary informed consent to participate in this clinical trial and to comply the directions including contraception after being fully informed of and understand this trial

Exclusion Criteria:

• Subjects who have the clinically significant diseases or history in liver, kidney, nervous system, respiratory system, endocrine system, blood tumor and cardiovascular system.
• Subjects who have participated in other clinical trial within 1 month prior to the first day of drug administration
• Subjects who are inappropriate in the judgement of the investigator due to the reasons including clinical laboratory test results