This chapter provides a description of physical and metabolic characteristics of persons with diabetes and prediabetes and is based primarily on data from the National Health and Nutrition Examination Surveys 2005–2010. The 2010 American Diabetes Association guidelines were used to define undiagnosed diabetes and prediabetes. Among participants with diabetes, mean glycosylated hemoglobin (A1c) concentrations were highest in those with diagnosed diabetes treated by insulin or oral diabetes medication (7.4%), followed by undiagnosed diabetes defined by A1c or fasting plasma glucose (6.9%), and lowest among those with untreated diagnosed diabetes (6.3%) and undiagnosed diabetes defined by A1c, fasting plasma glucose, or 2-hour plasma glucose (6.3%). Mean fasting plasma glucose concentrations were highest in those with treated diabetes (153 mg/dL) and undiagnosed diabetes defined by A1c or fasting plasma glucose (149 mg/dL) and generally lower among those with untreated diagnosed diabetes (137 mg/dL) and undiagnosed diabetes defined by A1c, fasting plasma glucose, or 2-hour plasma glucose (130 mg/dL). Mean 2-hour plasma glucose concentrations were higher in those with undiagnosed diabetes (243 mg/dL for A1c and fasting plasma glucose definition; 235 mg/dL for A1c, fasting plasma glucose, and 2-hour plasma glucose definition) than in people with untreated diagnosed diabetes (183 mg/dL; 2-hour plasma glucose was not measured in participants with treated diagnosed diabetes). Participants with prediabetes by definition had lower A1c, fasting plasma glucose, and 2-hour plasma glucose concentrations than those with diabetes, and participants with normal glucose regulation had the lowest concentrations. Mean fasting insulin concentrations were generally higher in people with undiagnosed diabetes than in people with diagnosed diabetes (insulin users were excluded). Participants with prediabetes generally had lower fasting insulin concentrations than those with undiagnosed diabetes, and those with normal glucose regulation had the lowest fasting insulin concentrations.

The prevalence of family history of diabetes was generally highest among people with diagnosed diabetes (69%), followed by undiagnosed diabetes (49% for A1c and fasting plasma glucose definition; 45% for A1c, fasting plasma glucose, and 2-hour plasma glucose definition), and was lowest in those with prediabetes (39%) and normal glucose regulation (33%). People with diabetes had higher mean body mass index and systolic blood pressure than people with prediabetes, and those with normal glucose regulation had the lowest means. The relationship between diabetes and cholesterol level differed by age group. Mean levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides were generally higher in people with diabetes age 20–44 years than in people with prediabetes or normal glucose regulation. Conversely, mean levels of total cholesterol, LDL cholesterol, and triglycerides were generally lower in people with diabetes age 45–64 years than those with prediabetes or normal glucose regulation. The prevalence of C-reactive protein ≥10 mg/L was generally higher among people with diabetes than among people with prediabetes, and people with normal glucose regulation generally had the lowest prevalence. Women with diagnosed diabetes had a higher age-standardized mean number of live births than women who had not been diagnosed with diabetes. Individuals with diagnosed diabetes reported a higher prevalence of fair or poor health than those with prediabetes or normal glucose regulation.