Hyperosmolar Hyperglycemic State (HHS)

HHS is about osmolality, not ketones. It is severe hyperglycemia with hyperosmolality and dehydration, and ketoacidosis is little or absent. The 2024 consensus asks for four things, and you need all of them. First, plasma glucose ≥600 mg/dL. Second, effective serum osmolality >300 mOsm/kg (or total osmolality >320 mOsm/kg). Third, BHB <3.0 mmol/L (or urine ketones less than 2+). Fourth, no acidosis: pH ≥7.30 and bicarbonate (HCO₃⁻) ≥15 mEq/L (consensus diagnostic table). A separate bicarbonate cut-off of 18 mEq/L, with pH ≥7.30, picks the insulin dose (see ED & ICU). Mental status is no longer a diagnostic criterion. It is still common, and it drives risk.

The insulin deficit is partial. It is enough to stop glucose getting into cells, but counter-regulatory hormones keep the liver pushing glucose out. Glucose climbs past the renal threshold and pulls water with it in an osmotic diuresis. Fluid and electrolytes go out with the urine. The rising osmolality dulls thirst and consciousness. Insulin is not short enough to drive the lipolysis and ketogenesis of DKA. That is why ketones stay low.

• Typical patient: older adult with type 2 diabetes, often with a reduced ability to drink water.
• Common triggers: infection, myocardial infarction, stroke, missed or reduced insulin or oral agents, poor oral intake, and medicines that raise glucose, such as glucocorticoids and antipsychotics. SGLT2 inhibitors are the trap here. They raise DKA risk, so a mixed picture becomes more likely.
• Course: Expect days of polyuria, thirst and weakness first. Then confusion, obtundation or seizure as osmolality climbs. Severe cases bring hypotension and thrombosis, and both are common.

Typical Presentation

Picture an older adult. Known or undiagnosed diabetes, days of thirst and polyuria, weakness, and dehydration: dry mucosa, reduced skin turgor, orthostatic symptoms. Confusion or drowsiness is common. A focal deficit, seizure or coma can be the first sign. Kussmaul breathing and fruity breath are DKA signs. In HHS they are usually absent or mild.

Red Flags

• Glucose ≥600 mg/dL with any change in mental status, or with hypotension
• Calculated effective osmolality above 300 mOsm/kg, or confusion with a glucose well above 600 mg/dL
• Decreasing responsiveness, seizure, focal neurologic deficit or a fall in GCS
• Hypotension, tachycardia, cool or mottled skin, or signs of shock
• Potassium below 3.5 mEq/L on any lab result, or suspected from ECG changes such as flat T waves or U waves (insulin must wait)
• Glucose below 70 mg/dL, especially in a patient taking insulin or a sulfonylurea

The bedside glucose and a basic chemistry make the diagnosis. Osmolality and pH tell you how sick the patient is. BHB separates HHS from mixed DKA/HHS. Potassium decides when insulin can start.

• Diabetic ketoacidosis (DKA): Ketones and acidosis are the tell, and glucose is often lower. Mixed DKA/HHS carries features of both. See Diabetic Ketoacidosis.
• Stroke or intracranial hemorrhage: A focal deficit, unilateral weakness or headache does not prove HHS, even with a high glucose. Image the head when a focal finding or trauma is present. See Acute Ischemic Stroke.
• Sepsis: Fever, hypotension and a rising lactate point to infection as the trigger. That infection must be treated alongside HHS. See Sepsis and Septic Shock.
• Hypoglycemia with altered mental status: A low glucose is the opposite finding, and it is treated first. See Hypoglycemia.
• Toxic or metabolic causes of confusion: Don't blame HHS alone for confusion yet. Check glucose, osmolality and the medication list first.

Every level runs the same pathway. Your BLS job is scene safety, airway, monitoring and early notification.

1. Scene safety and baseline: confirm the patient is responsive, check breathing and a fingerstick glucose if the protocol allows.
2. Airway and position: position on the side if vomiting or drowsy, suction as needed, and support oxygen to the SpO₂ target in the protocol.
3. Oral intake: none if the patient is confused, drowsy or vomiting. Do not give oral fluids or food to an unresponsive or confused patient.
4. Medications: document the insulin, oral diabetes drugs and last dose. Do not assist with insulin or oral hypoglycemics unless protocol and medical direction allow.
5. Monitor and transport: recheck mental status and vital signs in transit, and call early so the receiving team can prepare.

Doses vary by protocol; follow local protocols and medical direction.

• IV access and cardiac monitor (Paramedic/RN/CCT): establish IV access and monitor rhythm. Draw glucose, electrolytes, BUN, creatinine and, where the protocol allows, BHB, venous gas and osmolality, without delaying fluids.
• 12-lead ECG (Paramedic/RN/CCT): look for peaked T waves, QRS widening, or ischemia; treat hyperkalemia per protocol.
• Isotonic fluid (Paramedic/RN/CCT): 0.9% saline or a balanced crystalloid, started early. Hospital HHS care follows the fluid-first pathway: 500–1,000 mL/hr for 2–4 hr in patients without cardiac or renal compromise. Prehospital bolus size follows local protocol; use smaller boluses with lung reassessment in older adults, heart failure or end-stage kidney disease. See Normal Saline or Lactated Ringer's.
• Hypoglycemia (Paramedic/RN/CCT): treat per protocol with dextrose and recheck glucose after treatment. See Dextrose.
• No insulin prehospital: insulin is started in the ED or ICU after fluids have begun and potassium is known to be above 3.5 mEq/L. See Insulin.
• Potassium (Paramedic/RN/CCT): give only per protocol and only when the result or ECG supports it. Potassium below 3.5 mEq/L is replaced before insulin. See Potassium Chloride.
• Vomiting: control per protocol so fluids can be given. See Ondansetron.
• Airway (Paramedic/RN/CCT): intubation is rarely the first step, but a falling GCS or failing airway calls for RSI with hemodynamic support in place; hypotension at induction is common in dehydrated patients. See RSI.
• Seizure: treat per protocol and check glucose and sodium.

Fluids come first, then insulin. Potassium and glucose get adjusted together. The consensus correction targets are in the table below.

• Insulin (adult HHS): fixed-rate IV regular insulin at 0.05 units/kg/hr once fluid resuscitation has begun and potassium is above 3.5 mEq/L. Use 0.1 units/kg/hr for mixed DKA/HHS (BHB 3.0 mmol/L or above, urine ketones 2+ or more, pH below 7.30, or HCO₃⁻ below 18 mEq/L). Some have recommended holding insulin, with fluids alone, until glucose stops falling. The aim is to avoid a rapid fall in osmolality. See Insulin.
• Potassium: below 3.5 mEq/L, hold insulin and give IV potassium at 10 mEq/hr, then recheck. Once insulin starts, recheck K⁺ 2 hr later and every 4 hr. From 3.5 to 5 mEq/L, add potassium to fluids per protocol to hold about 4–5 mEq/L. Above 5 mEq/L, add none until rechecked. See Potassium Chloride.
• Fluid choice: 0.9% saline or balanced crystalloid, per local availability. The consensus notes balanced solutions were linked to less hyperchloremic acidosis, though most of that evidence comes from DKA. Once volume is restored, choose fluid by blood pressure, heart rate, intake and output, and sodium. Replace estimated deficits over 24–48 hr. As glucose falls, measured Na⁺ rises by about 1.6 mmol/L per 100 mg/dL glucose fall. That rise alone is no reason for hypotonic fluid. Use 0.45% saline only if osmolality is still not falling despite adequate positive fluid balance and insulin. Reassess volume status and lung findings at every check.
• Osmolality correction: The consensus caps the glucose fall at 90–120 mg/dL/hr, and the osmolality fall at 3–8 mOsm/kg/hr. Both limits guard against cerebral edema. The consensus also says serum sodium should not fall by more than 10 mmol/L in 24 hr.
• Bicarbonate: Not routine (consensus, DKA data). Consider it only if pH is below 7.0, per protocol. A pH below 7.30 falls outside pure HHS, so look for mixed DKA/HHS. See Sodium Bicarbonate.
• Phosphate: Routine replacement is not indicated. Consider it only if phosphate is below 1.0 mmol/L, with muscle weakness, or respiratory or cardiac compromise (consensus, DKA data).
• Subcutaneous insulin: Not recommended for HHS (consensus). Use the intravenous route.
• Thrombosis prevention: Prophylactic-dose low-molecular-weight heparin, unless thrombosis is suspected (consensus). With CrCl below 30 mL/min, the enoxaparin label gives 30 mg subcutaneously once daily for medical prophylaxis. Check renal function first, or follow protocol for an alternative such as unfractionated heparin. See Enoxaparin.
• Resolution: The consensus has no agreed definition of resolution. It does consider HHS resolved when osmolality is below 300 mOsm/kg, hyperglycemia is corrected (glucose below 250 mg/dL), urine output is above 0.5 mL/kg/hr and cognition has improved.
• Transition: Transition advice comes from the consensus, written for DKA and applied here by analogy. It uses a 1–2 hr overlap, with basal insulin started 1–2 hr before the infusion stops, per protocol.
• Disposition: ICU for coma, seizure, hypotension or falling mental status. A patient on an insulin infusion needs close monitoring, in ICU or step-down per local policy. Step-down fits the patient who is alert and stable on fluids alone.

• Destination: a hospital that can run an insulin infusion and manage HHS. ICU-capable hospital for coma, seizure, hypotension or falling mental status; pediatric-capable center for children.
• Keep running: IV access and fluid rate per protocol; cardiac monitor; repeat glucose per protocol and at least every 1–2 hr if an insulin infusion is running.
• Insulin in transit (CCT): dedicated line and pump; confirm bag concentration and pump rate against the order.
• Watch for overload: Crackles, rising work of breathing or falling SpO₂ in heart failure or kidney failure are your warning. Stop the bolus and reassess.
• Airway: protect it in a drowsy or vomiting patient; keep the respiratory pattern you found on scene.
• Handoff: symptom onset, glucose trend, fluid volume given, potassium if known, mental status, precipitant and time of last insulin dose.

• Pediatrics: HHS is uncommon in children. Fluid and insulin doses are weight-based and follow the pediatric DKA/HHS protocol. The ISPAD 2022 guideline covers both conditions (reference 3). Pediatric shock boluses follow the Pediatric Shock page. Cerebral edema is a serious DKA complication. In adults with HHS it is described as rare (consensus). In a child, any fall in mental status needs urgent reassessment per the pediatric DKA/HHS protocol. This page gives no doses. Find them at weight-based dosing and vital signs.
• Pregnancy: HHS in pregnancy is rare, and it carries fetal risk. Treat it as high risk. Bring the obstetric team in early, and use an obstetric-capable hospital. Pregnant patients are at risk of fluid overload. Give fluids cautiously, with frequent lung and volume reassessment. In later pregnancy, position them on the left side to relieve aortocaval compression.
• Older Adults: This is the usual HHS patient. Expect reduced thirst to delay the diagnosis. Use smaller boluses, with frequent hemodynamic and lung checks.
• Renal Impairment: Kidney failure raises the risk of fluid overload and hyperkalemia. Insulin clearance is reduced too. Reassess volume and potassium before each bolus or dose change.
• Hepatic Impairment: Impaired gluconeogenesis and low glycogen stores raise the hypoglycemia risk on insulin. Check glucose more often.
• Patients on Anticoagulants: Therapeutic anticoagulation already covers thrombosis, so don't add prophylactic LMWH on top. Check bleeding risk and renal function before you add any anticoagulant. With CrCl below 30 mL/min, enoxaparin prophylaxis is 30 mg SC once daily. Or use unfractionated heparin per protocol.
• Patients on SGLT2 Inhibitors: SGLT2 inhibitors raise DKA risk, which makes a mixed DKA/HHS picture more likely. The consensus advises stopping them on admission. Glucocorticoids and antipsychotics also raise glucose, so review the full medication list.
• Patients on Beta-Blockers: Adrenergic warning signs of hypoglycemia may be blunted. Rely on glucose checks and mental status.

• Error: Starting insulin before the potassium is known. Check potassium first. Below 3.5 mEq/L, replace it and hold the insulin.
• Error: A normal urine ketone test is not proof there is no crisis. Use osmolality and mental status. The BHB result decides HHS versus mixed DKA/HHS.
• Error: Anchoring on the glucose is the trap. A glucose of 600 mg/dL with confusion may still be a stroke, infection or MI. Check for each trigger.
• Error: Correcting osmolality too fast, with big boluses or fast insulin. Hold to the consensus limits and recheck every 4 hr.
• Error: Stopping insulin once glucose drops below 250 mg/dL. Add dextrose and keep the infusion running until the endpoints are met.
• Error: Ignoring pulmonary edema in older adults or heart failure. Reassess the lungs after every bolus.
• Warning: Hypoglycemia after insulin is common. Mental status may not recover quickly, so check glucose at each interval.