Type 2 diabetes mellitus in adults

The cornerstone of therapy for all patients with type 2 diabetes is a personalized self-management program, usually developed with the patient by a diabetes education nurse or nutritionist.

Lifestyle changes plus metformin are initial antihyperglycemic therapy for most patients. Glycemic goals and treatment choices are individualized. Due to the progressive nature of the condition, it often requires escalation/combination of therapy.

Blood pressure control, lipid management (statin therapy), smoking cessation, and glycemic management reduce the risk of macrovascular complications such as heart attack and stroke. Glycemic control and blood pressure management reduce the risk of microvascular complications (neuropathy, nephropathy, retinopathy).

Type 2 diabetes mellitus is a progressive disorder defined by deficits in insulin secretion and action that lead to abnormal glucose metabolism and related metabolic derangements.[1]Meigs JB, Muller DC, Nathan DM, et al. The natural history of progression from normal glucose tolerance to type 2 diabetes in the Baltimore Longitudinal Study of Aging. Diabetes. 2003 Jun;52(6):1475-84. https://diabetes.diabetesjournals.org/content/52/6/1475.full http://www.ncbi.nlm.nih.gov/pubmed/12765960?tool=bestpractice.com Although the etiologies of type 1 and type 2 diabetes differ dramatically, both lead to hyperglycemic states, and both share common macrovascular (coronary heart, cerebrovascular, and peripheral vascular disease) and microvascular (retinopathy, nephropathy, and neuropathy) complications.

Type 2 diabetes is most often diagnosed following routine screening. It is preceded by a state of prediabetes, which is defined by a single fasting plasma glucose (FPG) of 100-125 mg/dL (5.6 to 6.9 mmol/L), or plasma glucose of 140-199 mg/dL (7.8 to 11.0 mmol/L) 2 hours after 75 g oral glucose, or a hemoglobin A1c (HbA1c) of 5.7% to 6.4% (39-47 mmol/mol) in the absence of diabetes.[2]American Diabetes Association. Standards of care in diabetes - 2023. Diabetes Care. 2023 Jan 1;46(suppl 1):S1-291. https://diabetesjournals.org/care/issue/46/Supplement_1 In the absence of unequivocal hyperglycemia, diabetes diagnosis is based on two confirmed values of: FPG ≥126 mg/dL (≥7.0 mmol/L), plasma glucose ≥200 mg/dL (≥11.1 mmol/L) 2 hours after 75 g oral glucose, or HbA1c of ≥6.5% (≥48 mmol/mol).[2]American Diabetes Association. Standards of care in diabetes - 2023. Diabetes Care. 2023 Jan 1;46(suppl 1):S1-291. https://diabetesjournals.org/care/issue/46/Supplement_1 Alternatively, diabetes can be diagnosed with a single random plasma glucose of ≥200 mg/dL (≥11.1 mmol/L) plus symptoms of hyperglycemia or hyperglycemic crisis.[2]American Diabetes Association. Standards of care in diabetes - 2023. Diabetes Care. 2023 Jan 1;46(suppl 1):S1-291. https://diabetesjournals.org/care/issue/46/Supplement_1 A single blood sample is sufficient to establish a diabetes diagnosis if assays of both HbA1c and FPG meet criteria for diabetes diagnosis.[2]American Diabetes Association. Standards of care in diabetes - 2023. Diabetes Care. 2023 Jan 1;46(suppl 1):S1-291. https://diabetesjournals.org/care/issue/46/Supplement_1

Management of glycemia in patients with type 2 diabetes who have or are at high risk for comorbid chronic kidney disease, heart failure, or atherosclerotic cardiovascular disease is beyond the scope of this topic. See Diabetic kidney disease and Diabetic cardiovascular disease.

Coronavirus disease 2019 (COVID-19) and diabetes:

- See our separate topic Management of coexisting conditions in the context of COVID-19

- Further diabetes resources are available at:

American Diabetes Association: COVID-19 professional resources Opens in new window

Association of British Clinical Diabetologists: COVID-19 (coronavirus) information for healthcare professionals Opens in new window