DMAIC: Define, Measure, Analyze, Improve, Control. LSL: Lower specified limit. USL: Upper specified limit. Lean Six Sigma DMAIC is quality improvement methodology used for strategic business management. Frequent applications of this methodology in healthcare include improvement of patient satisfaction, reduction of emergency department waiting times, prescription error reduction and monetary recovery by reducing waste. Patients with a HgbA1c testing frequency of >6 months have poorer glycemic control. The American Diabetes Association recommends HgbA1c test quarterly in patients whose therapy has changed or who are not meeting glycemic goals and at least two times a year in patients who are meeting treatment goals. We hypothesized that the Lean Six-Sigma DMAIC tools can be used in the outpatient clinic setting to improve frequency of HgbA1c testing in patients with diabetes mellitus. At baseline, 19% of our patients with diabetes mellitus had HgbA1c tested infrequently, defined as more than 6 months. This high percentage is a concern as it could lead to poor diabetes control. The aim was to increase percentage of patients having an HgbA1c tested between 3 to 6 months before an appointment in our clinic, to a goal of 90%. Target population included all patients with diabetes mellitus seen in outpatient endocrinology clinic. A baseline analysis of existing processes was done through brainstorming with the clinic staff using a fish bone diagram. Lack of follow up and HgbA1c testing orders were some of the modifiable factors identified. The new processes implemented include nurse driven standing medical orders for HgbA1c testing and pre-visit planning. Control phase included regular audits to sustain the improvements. The percentage of patients with a HgbA1c testing within 3-6 months of appointment improved from a baseline of 76.7% (LSL:70%, USL:94%) to 92.2% (LSL:88%, USL:93.7%). The improvement was noticeable within 1 month of new process implementation and continues to sustain. The mean had an absolute improvement of 15.5%. The variation from the mean decreased from 25% at baseline to 6% at the end of the control phase. The reduction in variation made our future results more predictable. The use of Lean Six-Sigma DMAIC quality improvement tools are an effective method to improve quality of care in the outpatient setting. These strategies can be replicated for other clinical quality outcomes.