Inclusion Criteria:

- Male or female, all races and ethnicities are eligible

- Age equal to or greater than 18 years of age

- All subjects should have a pathological/histological diagnosis of colorectal cancer.

- Clinical diagnosis of stage I, II, III or IV colon cancer or stage I, II, III or IV
rectal cancer; cancer may be primary including a secondary primary

- Candidate for elective surgery(for removal of primary) or endoscopic biopsy

- ECOG Performance status of 0 - 2

- Adequate renal, liver, and bone marrow function

- Hb: (adequate for surgical intervention, with transfusion if necessary)

- WBC: (normal range)

- Platelets: (180K/cmm)

- LFTs: Normal bilirubin (< 2.0mg/dL), AST/ALT (2xULN)

- Renal function: normal creatinine

- Subjects must have signed informed consent

- Female subjects must either not be of child-bearing potential or must have a negative
urine pregnancy test within 7 days of beginning the drug or placebo treatment.
Subjects are considered not of child-bearing potential if they are surgically sterile
or they are postmenopausal for greater than 12 months.

Exclusion Criteria:

- Previously diagnosed with diabetes mellitus Type 1 or Type 2.

- Currently taking biguanides, sulfonylurea drugs, thiazolidinediones, insulin, or mTOR
inhibitors or having taken any of these medications during the 12 weeks prior to
study participation.

- Currently taking any non-steroidal anti-inflammatory drugs (NSAIDs) or aspirin and
unable to stop such medications due to a present medical condition.

- Clinical symptoms of gastrointestinal obstruction or bleeding and consideration for
immediate surgery or immediate neoadjuvant chemoradiation.

- Familial Adenomatous Polyposis (FAP), hereditary non-polyposis colorectal cancer
(HNPCC), Putz-Jeghers disease, ulcerative colitis, or Crohn's disease.

- Pregnant or lactating.

- History of lactic or other metabolic acidosis.

- Known hypersensitivity to Metformin.

- Uncontrolled infectious disease.

- History of Positivity for human immunodeficiency virus (HIV).

- History of congestive heart failure requiring pharmacologic treatment.

- History of excessive alcohol abuse, defined by a habitual intake of more than three
drinks daily.

- Previous or concurrent malignancies, except non-melanoma skin cancers, unless
curatively treated and with no evidence of recurrence for > 5 years, with the
exception of prior CRC which has been treated and the patient has been in remission
and the current primary tumor is a second CRC.

- Unable to swallow and retain oral medication.

- Mal-absorption syndrome, disease affecting gastrointestinal function, or previous
resection of the stomach or small bowel.

- Current use of medications for weight loss.

- Currently taking cimetidine, thiazide diuretics or cephalexin. If a patient needs
some of these agents, alternative agents should be substituted.

- If the physician feels that the candidate is not suitable for the study, he/she will
be excluded.