At what blood glucose level should a patient, especially one with a history of diabetes or cardiovascular disease, be sent to the emergency room (ER)?

Blood Glucose Thresholds for Emergency Room Referral

Patients should be sent to the ER when blood glucose is ≥250 mg/dL with symptoms of hyperglycemic crisis, ≥600 mg/dL regardless of symptoms, or <50 mg/dL with altered mental status or inability to self-treat. 1, 2

Critical Hyperglycemia Thresholds

Immediate ER Transfer Required

• Blood glucose ≥250 mg/dL (13.9 mmol/L) with symptoms of diabetic ketoacidosis (DKA) or hyperglycemic hyperosmolar state (HHS) such as nausea, vomiting, altered mental status, or severe dehydration 1, 2

• Blood glucose ≥600 mg/dL (33.3 mmol/L) regardless of symptoms, as this indicates potential HHS 2

• Blood glucose ≥180 mg/dL (10.0 mmol/L) accompanied by vomiting, dehydration, or altered mental status 2

• Blood glucose persistently >250 mg/dL over 2 consecutive days despite home management 2

• Any glucose reading >350 mg/dL should trigger physician notification and consideration for ER evaluation 3

The American Diabetes Association specifically identifies blood glucose ≥250 mg/dL with symptoms or ≥500 mg/dL without symptoms as constituting emergent hyperglycemia requiring immediate medical attention. 1 The presence of ketones in blood (>2 mmol/L) or urine with hyperglycemia >250 mg/dL strongly suggests DKA and mandates emergency evaluation. 1

Special Hyperglycemic Considerations

Patients on SGLT2 inhibitors can develop DKA with glucose <200 mg/dL (euglycemic DKA), so ER referral is warranted even at lower glucose levels if symptoms of DKA are present. 2 This is particularly important with risk factors including very-low-carbohydrate diets, prolonged fasting, dehydration, or excessive alcohol intake. 2

Pregnant patients with diabetes may present with euglycemic DKA and should be sent to the ER with any concerning symptoms regardless of glucose level. 2

Critical Hypoglycemia Thresholds

Immediate ER Transfer Required

• Blood glucose <50 mg/dL (<2.8 mmol/L) with altered mental status, confusion, combativeness, somnolence, lethargy, seizures, or coma 3

• Blood glucose <60 mg/dL (<3.3 mmol/L) if the patient cannot self-treat or requires third-party assistance 3

• Any severe hypoglycemia defined as requiring assistance from another person, regardless of the specific glucose value 3

The 2014 American Diabetes Association guidelines define hypoglycemia as blood glucose <70 mg/dL (3.9 mmol/L), but severe hypoglycemia requiring ER evaluation is characterized by the need for third-party assistance and mental status changes. 3 Hypoglycemia <50 mg/dL is associated with significant neurological manifestations including obtundation, stupor, coma, confusion, bizarre behavior, seizures, and even focal deficits like hemiparesis. 4

Hypoglycemia Management Before Transfer

If glucagon is available and staff are trained, administer glucagon intramuscularly or intravenous glucose for severe hypoglycemia before transport. 3 If the patient is conscious and able to swallow, give 15-20 grams of oral glucose and recheck glucose in 15 minutes, repeating until glucose ≥70 mg/dL. 3 However, do not delay ER transfer for patients with altered mental status or inability to protect their airway. 3

Clinical Context and Warning Signs

Hyperglycemic Crisis Indicators

Beyond the absolute glucose values, send patients to the ER when hyperglycemia is accompanied by:

• Nausea or vomiting, which may indicate DKA 3
• Kussmaul respirations (deep, labored breathing suggesting metabolic acidosis) 2
• Profound dehydration with poor skin turgor and hypotension 2
• Altered mental status ranging from confusion to coma 2
• Abdominal pain that could represent either a cause or consequence of DKA 2
• Inability to tolerate oral hydration 2
• Failure to improve with home insulin administration 2

Hypoglycemia Risk Factors Requiring Lower Threshold

Consider ER referral at higher glucose thresholds (e.g., <60 mg/dL rather than <50 mg/dL) for patients with:

• History of recurrent severe hypoglycemia or hypoglycemia unawareness 3
• Advanced age (>65 years), as elderly patients have impaired counterregulatory responses and may not manifest typical warning symptoms 3
• Renal insufficiency, which impairs gluconeogenesis and insulin clearance 3
• Sepsis or severe illness, which increases hypoglycemia risk 3
• Alcohol intoxication, as symptoms can be confused with hypoglycemia 3

Common Pitfalls to Avoid

Do not assume normal mental status excludes severe hypoglycemia or hyperglycemia. There is considerable overlap between glucose levels and symptoms, and some patients remain relatively asymptomatic despite dangerous glucose values. 4

Do not confuse hypoglycemia with intoxication or withdrawal. Signs like altered mental status, agitation, and diaphoresis overlap significantly, and glucose should be checked immediately in any patient with diabetes exhibiting these symptoms. 3

Do not wait for laboratory confirmation if clinical suspicion is high. Point-of-care glucose testing should be performed immediately, and treatment/transfer should not be delayed for formal lab results. 3

Do not underestimate euglycemic DKA. Approximately 10% of DKA cases present with glucose <200 mg/dL, particularly in patients on SGLT2 inhibitors, pregnant patients, or those with reduced food intake. 2