Emergency & Acute Care

Hyperosmolar Hyperglycaemic State (HHS) — Clinical Reference

Last reviewed 2026-06-16 · TruelyserMD Clinical Reference
For Patients & General Readers

Hyperosmolar Hyperglycaemic State (HHS) is a serious complication of diabetes, most often seen in type 2 diabetes. It happens when blood sugar levels become extremely high, leading to severe dehydration and confusion. Prompt medical attention is crucial to prevent life-threatening complications like coma.

Clinical Overview

HHS is a hyperglycaemic crisis characterized by profound dehydration, hyperosmolarity, and altered mental status in the absence of significant ketoacidosis. It typically occurs in individuals with type 2 diabetes and is often precipitated by an underlying illness or event.

Clinical Presentation

Signs & Symptoms

Symptoms (Patient-Reported)

  • Extreme thirst (polydipsia)
  • Frequent urination (polyuria)
  • Severe dehydration
  • Confusion or disorientation
  • Drowsiness or lethargy
  • Weakness and fatigue
  • Nausea and vomiting

Signs (Clinician-Observed)

  • Dry mucous membranes
  • Sunken eyes
  • Poor skin turgor
  • Tachycardia
  • Hypotension
  • Neurological deficits (e.g., focal neurological signs, seizures)

Differential Diagnoses

ConditionDistinguishing Feature
Diabetic Ketoacidosis (DKA)DKA is characterized by significant ketosis (ketonuria/ketonemia) and metabolic acidosis, whereas HHS has minimal ketosis and no significant acidosis.
StrokeStroke presents with focal neurological deficits that may not be directly related to hyperglycemia or dehydration. HHS can cause neurological symptoms but typically due to hyperosmolarity and dehydration.
SepsisSepsis can cause hyperglycemia and altered mental status, but usually presents with signs of infection (fever, leukocytosis) and may not have the profound hyperosmolarity seen in HHS.
UremiaUremia can cause altered mental status and dehydration, but typically has elevated BUN and creatinine, and may have metabolic acidosis without significant hyperglycemia.
Hyperglycemic Hyperosmolar Nonketotic Coma (HHNC)This is essentially synonymous with HHS.
Medication Side Effects (e.g., diuretics, steroids)These can cause dehydration and electrolyte imbalances, but typically do not lead to the extreme hyperglycemia and hyperosmolarity seen in HHS without a predisposing diabetic state.

Red Flags — Seek Immediate Care

Key Investigations

Management Overview

Management of HHS involves aggressive fluid resuscitation to correct dehydration and hypovolemia, followed by careful insulin administration to lower blood glucose. Electrolyte replacement, particularly potassium, is critical, and treatment of precipitating factors is essential for recovery.

Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. TruelyserMD does not replace clinical judgement.