Things We Do For No Reason: Sliding-Scale Insulin as Monotherapy for Glycemic Control in Hospitalized Patients

Inspired by the ABIM Foundation's Choosing Wisely campaign, the “Things We Do for No Reason” (TWDFNR) series reviews practices that have become common parts of hospital care but may provide little value to our patients. Practices reviewed in the TWDFNR series do not represent “black and white” conclusions or clinical practice standards but are meant as a starting place for research and active discussions among hospitalists and patients. We invite you to be part of that discussion. https://www.choosingwisely.org/

A 60-year-old man with a past medical history of obesity and type 2 diabetes presented to the emergency department with one week of myalgias and fever up to 103.5°F (39.7°C). Other vital signs were normal. He had no localizing symptoms, and physical examination was unrevealing, except for a small scab from a tick bite sustained two weeks prior to symptom onset. Before admission, he had been managing his diabetes with metformin 1,000 mg twice a day, and on arrival, his blood sugar level was 275 mg/dL. The admitting provider decided to hold the patient’s metformin and replace it with insulin per a sliding scale. Is monotherapy with sliding-scale insulin the best inpatient management option for this patient’s type 2 diabetes?

The basic premise of sliding-scale insulin (SSI) is to correct hyperglycemia through the frequent administration of short-acting insulin dosed according to a patient’s blood glucose level with the help of a prespecified rubric. When blood glucose levels are low, patients receive little or no insulin, and when blood glucose levels are high, higher doses are given. This approach to inpatient blood glucose management was first popularized by Joslin in 1934,¹ and it remains a common strategy today. For example, a 2007 survey of 44 hospitals in the United States showed that approximately 43% of all noncritically ill patients with hyperglycemia were treated with SSI alone.² More recently, a single-center study showed that 30% of clinicians continued to use SSI as monotherapy even after the implementation of order sets designed to limit this practice.³

The rationale for SSI as monotherapy appears to have two components. First, guidelines suggest that certain patients should be screened periodically in the hospital for hyperglycemia (blood glucose persistently greater than 180 mg/dL) and that, if identified, hyperglycemia should be treated.⁴ By pairing finger-stick glucose monitoring with SSI, the diagnosis and treatment—although not the prevention—of hyperglycemia can be accomplished simultaneously. Second, inpatient providers do not want to cause harm in the form of hypoglycemia. SSI as monotherapy is sometimes viewed as a cautious approach in this regard as insulin is administered only if the blood sugar level is high.

Convenience is probably another key contributor to the enduring use of SSI as monotherapy. Several hospitals have ready-made order sets for SSI that are easier to prescribe than a patient-specific regimen including both short- and long-acting insulin. In at least one single-center survey, physicians and staff were found to favor convenience over perceived efficacy when asked about their attitudes toward inpatient glycemic control.⁵ Although efforts at individual hospitals to change practice patterns among residents have shown promise,⁶ reform on a broader scale remains elusive.