Yes, Type 1 Diabetics Can Develop HHNK (HHS)
Although hyperosmolar hyperglycemic state (HHS) is classically associated with type 2 diabetes, patients with type 1 diabetes can and do develop HHS, though it occurs less commonly than diabetic ketoacidosis (DKA). 1
Key Evidence from Guidelines
The American Diabetes Association's 2004 position statement explicitly states that "these disorders can occur in both type 1 and type 2 diabetes," referring to both DKA and HHS 1. This definitively answers your question—type 1 diabetics are not immune to HHS.
Why This Happens
The pathophysiology explains why type 1 diabetics can develop HHS:
- HHS occurs when plasma insulin concentrations are inadequate for glucose utilization but adequate (as determined by residual C-peptide) to prevent lipolysis and ketogenesis 1
- Even in type 1 diabetes, there may be enough residual insulin activity to suppress ketone production while still allowing severe hyperglycemia and hyperosmolarity to develop
- The evidence for this mechanism is acknowledged as weak, but clinical cases confirm it occurs 1
Clinical Reality: Case Reports Confirm This
Multiple recent case reports document HHS as the first presentation of type 1 diabetes in children and adolescents:
- A 2022 case of an adolescent male presenting with HHS and positive anti-GAD antibodies confirming T1DM 2
- A 2017 case of a 7-year-old girl with HHS as first presentation of T1DM 3
- A 2021 case of a 7-year-old boy with extremely high glucose (115 mmol/L) and HHS with T1DM 4
Diagnostic Criteria to Distinguish HHS from DKA
When evaluating a type 1 diabetic with hyperglycemia, use these criteria 1:
HHS characteristics:
- Plasma glucose ≥600 mg/dL
- Arterial pH >7.30
- Serum bicarbonate ≥15 mEq/L
- Small or absent ketones (key distinguishing feature)
- Effective serum osmolality ≥320 mOsm/kg
- Altered mental status more common than in DKA
DKA characteristics:
- Plasma glucose typically >250 mg/dL
- Arterial pH <7.30
- Serum bicarbonate <15 mEq/L
- Positive ketones (prominent feature)
- Variable osmolality
Critical Clinical Pitfalls
Don't assume all hyperglycemic type 1 diabetics have DKA—check osmolality and ketones to distinguish HHS from DKA 1
Mixed presentations occur—some patients can have overlapping features of both DKA and HHS 5
HHS has higher mortality (15%) than DKA (5%), so recognition is critical 1
The evolution differs: HHS typically develops over days to weeks, while DKA in type 1 diabetes usually evolves within 24 hours 1
Bottom Line for Practice
When a type 1 diabetic presents with severe hyperglycemia, measure serum osmolality and ketones to determine if they have DKA, HHS, or a mixed picture. The treatment approach differs, particularly regarding the rate of fluid replacement and insulin administration. HHS requires more gradual correction to avoid cerebral edema and osmotic demyelination syndrome 5.