Management of Hyperglycemia <300 mg/dL in the Emergency Department
For mild hyperglycemia (<300 mg/dL) in the ER, insulin therapy is NOT routinely indicated unless the patient has persistent hyperglycemia ≥180 mg/dL on two separate measurements or is critically ill. 1
Threshold for Insulin Initiation
The decision to treat hyperglycemia in the ER depends on the severity and clinical context:
Insulin therapy should be initiated only when blood glucose is persistently ≥180 mg/dL (10.0 mmol/L) checked on two occasions, not at the <300 mg/dL threshold mentioned in your question 1
For blood glucose between 140-180 mg/dL, observation and monitoring are appropriate without active insulin treatment in most non-critically ill patients 1
Blood glucose >300 mg/dL represents a quality measure threshold where the Centers for Medicare and Medicaid Services tracks hospital-acquired hyperglycemic events, but this does not automatically mandate ER treatment 1
Clinical Context Matters
When to Treat in the ER (even if <300 mg/dL):
Critically ill patients requiring ICU admission should receive insulin therapy for persistent hyperglycemia ≥180 mg/dL, targeting 140-180 mg/dL 1
Patients with diabetic ketoacidosis or hyperosmolar hyperglycemic state require immediate continuous insulin infusion regardless of the specific glucose level 1
Patients with acute myocardial infarction or ischemic stroke may warrant more aggressive glucose control, though intensive lowering has not shown additional benefit and increases hypoglycemia risk 1
When NOT to Treat in the ER:
For stable, non-critically ill patients with glucose <300 mg/dL who will be discharged home, ER insulin treatment is generally not indicated 1
Higher glucose ranges up to 200 mg/dL (11.1 mmol/L) are acceptable in settings where close nursing supervision is not feasible, which often applies to busy ERs 1
The acceptable range extends to 216 mg/dL (12.0 mmol/L) per UK guidelines, though this lower threshold has been questioned due to hypoglycemia risk 1
Practical ER Management Algorithm
For glucose 140-180 mg/dL:
For glucose 180-300 mg/dL:
- Recheck glucose in 2 hours to confirm persistent elevation 1
- If persistently ≥180 mg/dL on two occasions, consider subcutaneous insulin protocol with rapid-acting insulin every 2 hours until glucose <200 mg/dL 3
- This approach reduced subsequent hospital length of stay by 1.5 days (3.8 vs 5.3 days) in one study 3
For glucose >300 mg/dL:
- Initiate basal-bolus insulin regimen if admitting to hospital 4, 2
- For discharge home, consider sulfonylurea (glipizide XL 10 mg daily) with or without insulin glargine 10 units daily as a safe bridge therapy 5
- This discharge regimen achieved safe glucose control in 87% of patients with severe hyperglycemia 5
Critical Pitfalls to Avoid
Never use sliding-scale insulin alone as monotherapy in the ER or hospital, as it is associated with poor outcomes and inadequate glycemic control 1, 4, 2
Avoid aggressive glucose targets <140 mg/dL in the acute ER setting, as intensive control increases hypoglycemia risk 10-15 fold without mortality benefit 1
Do not discharge patients on premixed insulin (70/30), as it has an unacceptably high hypoglycemia rate in the outpatient transition period 4
Ensure potassium is ≥4.0 mEq/L before starting insulin therapy, as hypoglycemia during treatment occurs in 50% of patients and severe hypokalemia (<2.5 mEq/L) is associated with increased mortality 1
Monitoring Requirements
Point-of-care glucose testing every 2 hours is required when using rapid-acting insulin protocols in the ER 3
For patients being admitted, glucose monitoring should occur every 4-6 hours initially, with increased frequency if glucose >250 mg/dL or <70 mg/dL 4
If hypoglycemia (<70 mg/dL) occurs, reduce the responsible insulin component by 20-50% and establish a hypoglycemia management protocol 4