Typical Serum Glucose in Hyperosmolar Hyperglycemic State (HHS)
The typical serum glucose level in HHS is ≥600 mg/dL, which serves as the diagnostic threshold established by the American Diabetes Association. 1, 2
Diagnostic Glucose Threshold
Blood glucose ≥600 mg/dL is the defining criterion for HHS diagnosis, distinguishing it from diabetic ketoacidosis (DKA) where the threshold is only ≥250 mg/dL 1, 2
The glucose elevation in HHS is typically much more severe than in DKA, with many patients presenting with levels well above 600 mg/dL 3, 4
In documented case reports, glucose levels have been observed as high as 1,456 mg/dL in adolescent patients presenting with HHS 5
Clinical Context of Hyperglycemia in HHS
HHS develops over days to a week (unlike DKA which develops over hours to days), allowing glucose to reach these extremely elevated levels 2
The severe hyperglycemia occurs without significant ketoacidosis (ketones ≤3.0 mmol/L, pH ≥7.30, bicarbonate ≥15 mEq/L), which is the key metabolic distinction from DKA 1, 2, 6
Effective serum osmolality ≥320 mOsm/kg H₂O accompanies the hyperglycemia, calculated as: 2[measured Na (mEq/L)] + glucose (mg/dL)/18 1, 2
Treatment Target Glucose Levels
Once treatment is initiated, plasma glucose should decrease at 50-75 mg/dL per hour with fluid resuscitation and insulin therapy 1
When glucose reaches 300 mg/dL, decrease insulin infusion rate to 0.05-0.1 U/kg/h (3-6 U/h) and add dextrose (5-10%) to IV fluids 1, 2
Target glucose of 10-15 mmol/L (180-270 mg/dL) in the first 24 hours is recommended by the Joint British Diabetes Societies 6
HHS resolution criteria include blood glucose <15 mmol/L (270 mg/dL) along with osmolality <300 mOsm/kg and correction of hypovolemia 6
Important Clinical Pitfall
- Do not withhold insulin until glucose stops falling with IV fluids alone unless ketonemia is absent, as this older recommendation has been superseded by current guidelines recommending insulin initiation once renal function is assured and potassium ≥3.3 mEq/L 2