1.1. Background

Insulin is a hormone that is typically produced and secreted from pancreatic beta cells in response to elevated blood glucose by binding to receptors found on the liver, skeletal muscle, and adipose tissue cells. Carbohydrate, protein, and fat metabolism are regulated by insulin through suppressing hepatic glucose production, stimulating tissue glucose uptake, and suppressing free fatty acid release from adipose tissue. Subsequently, blood glucose levels are reduced through insulin’s mechanism. 1-3

However, there is inadequate or no insulin secretion in type 1 diabetes mellitus (DM), and there is insulin deficiency and resistance in type 2 DM. Therefore, patients with type 1 DM require insulin treatment to survive; patients with type 2 DM may require insulin when other antidiabetic agents are not able to effectively control blood glucose levels. If either type 1 or 2 DM are left untreated and/or uncontrolled, chronic hyperglycemia may lead to micro- and macrovascular complications, such as retinopathy, nephropathy, neuropathy, hypertension, dyslipidemia, and cardiovascular disease. 1-7

Exogenous insulin products are FDA-approved for use in type 1 and 2 DM. These products are used to mimic the physiologic pattern of insulin secretion. Phase 1 is basal insulin secretion, which suppresses hepatic glucose production in order to maintain blood glucose levels throughout the day. Phase 2 is increased insulin secretion in response to carbohydrate intake in order to lower postprandial blood glucose levels. Patients with type 1 DM require both basal and preprandial insulin boluses, while patients with type 2 DM may require basal and/or preprandial insulin boluses in addition to oral antidiabetic agents, diet, exercise, and weight reduction depending on the severity of their disease and glycemic control. 1-7

Glycemic targets recommended by the American Diabetes Association (ADA) and American Association of Clinical Endocrinologists and American College of Endocrinology (AACE/ACE) guidelines are summarized in Table 1 2, 8, 9. However, these targets should be individualized based on patient factors, such as life expectancy, severity of disease, comorbidities, and hypoglycemic risk. 2,8,9

Table 1. 2021 ADA & 2020 AACE/ACE General Glycemic Target Recommendations2, 8-10
Glycemic TargetsADA – Type 1 and 2AACE/ACE – Adult Type 2
Hemoglobin A1c

Adults & Pediatrics: less than 7%
Adults greater than 65 years:

  • Healthy: less than 7.0-7.5%
  • Complex/ intermediate health: less than 8.0%
  • Very complex/ poor health: Avoid hypoglycemia & symptomatic hyperglycemia
Greater than or less than 6.5%
Preprandial blood glucose

Adults: 80–130 mg/dL
Pediatrics: 90–130 mg/dL*
Adults greater than 65 years:

  • Healthy: 80–130 mg/dL
  • Complex/intermediate health: 90-150 mg/dL
  • Very complex/ poor health: 100-180 mg/dL
Less than 110 mg/dL
Postprandial blood glucoseAdults: less than 180 mg/dLLess than 140 mg/dL
Bedtime blood glucose

Adults & Pediatrics: 90–150 mg/dL*
Adults Greater than 65 years:

  • Healthy: 80-180 mg/dL
  • Complex/ intermediate health: 100-180 mg/dL
  • Very complex/ poor health: 110-200 mg/dL
N/A

Legend:

  • ! Less stringent A1c goals of less than 7.5% may be appropriate in pediatric and adolescent patients who cannot articulate hypoglycemia symptoms; have hypoglycemia unawareness; lack access to analog insulins, advanced insulin delivery technology, and/or continuous glucose monitoring; cannot check blood glucose regularly, or have nonglycemic factors that increase A1c. A goal of less than 8.0% may be appropriate in pediatric an adolescent patients with a history of severe hypoglycemia, limited life expectancy, or where harms of treatment outweigh the benefits
  • * Recommendations carried over from 2019 ADA Standards of Medical Care in Diabetes since they are not presented in the 2021 guidelines.