This is a prospective, randomized, non-blinded interventional study that will investigate the effect of a vitamin D supplement on HbA1c in patients with uncontrolled type 2 diabetes mellitus (DM) and vitamin D deficiency. The goal is to investigate whether correcting vitamin D deficiency will alter the HbA1c level in patients with type 2 DM and lower than normal vitamin D level. My hypothesis is that correcting vitamin D deficiency decreases HbA1c levels in patients with type 2 DM and vitamin D deficiency.

The total number of study subjects expected to be enrolled in this study is about 150. Study subjects included in this study will be men and women between 34-69 years of age who have been diagnosed with type 2 DM based on at least one of the American Diabetic Association criteria. These criteria are 1) fasting blood glucose higher than 125 mg/dL once with symptoms of diabetes (increased urination, increased appetite, increased thirst) or two times without symptoms; 2) random blood glucose more than 200 mg/dL once with symptoms or two times without symptoms of diabetes; 3) two hour glucose tolerance test more than 200 mg/dL once with symptoms or two times without symptoms; or 4) a random glycosylated hemoglobin more than 6.5 % two times. The age group for this research was selected based on the review of the literature on diabetes and vitamin D. Patients with known primary hyperparathyroidism, sarcoidosis, tuberculosis, cancer, potential terminal illness, history of serum creatinine more than 2.0 mg/dL, vitamin D supplement more than 200 IU/day, inflammatory bowel disease and history of hypercalcemia and kidney stones will be excluded from this study. For this project, vitamin D deficiency is defined as serum vitamin D level lower than 30 ng/mL and uncontrolled diabetes is defined as HbA1C level above 7.0. Although there is more than one recommended normal level of vit. D in the blood, most experts agree that the optimum serum level of vitamin D should be above 30 ng/mL. All subjects will be receiving standard of care for DM offered to them by his or her physician.

The investigators will investigate if different but fixed doses of vitamin D (600 IU a day vs 50,000 IU once every other week) when given to patients with type 2 DM and vitamin D deficiency have different effects on HbA1c level at the end of 24 weeks. A baseline blood draw, and fasting blood draws will be taken at 12 and 24 weeks for blood sugar levels, Vit D levels, and HgbA1c. Subjects with vitamin D deficiency will be randomly assigned to either group 1 or 2 and will be supplemented with either 600 IU of vitamin D/day (Group 1) or 50,000 IU of vitamin D every 2 weeks for 24 weeks (Groups 2). Patients who are not vitamin D deficient will be followed as the control group (Group 3) and will not be given any vitamin D supplement.Research subjects will be advised not to take any vitamin D or multivitamin while participating in this study. Subjects will be given 100 tablets of 600 IU of vitamin D in a bottle if they belong to Group 1. If they have been advised to take vitamin D 50,000 IU once every 14 days (Group 2), they will be given altogether 13 tablets of 50,000 of vitamin D each in a separate brown envelope with date written on the envelop and subjects will be asked to take vitamin D only on the date written on the envelop.

Inclusion Criteria:

• Type 2 diabetes mellitus
• Hgb A1c greater then 7.0
• Adults aged 34 to 69 years.

Exclusion Criteria:

• known primary hyperparathyroidism, sarcoidosis, tuberculosis, cancer, potential terminal illness,
• history of serum creatinine more than 2.0 mg/dL,
• vitamin D supplement more than 200 IU/day
• history of inflammatory bowel disease, hypercalcemia or kidney stones