Hyperglycemia, DKA, and HHS
Key Takeaways
- DKA is diagnosed with hyperglycemia (glucose >=200 mg/dL or known diabetes), ketosis (beta-hydroxybutyrate >=3.0 mmol/L), and metabolic acidosis (pH <7.3 or bicarbonate <18 mEq/L).
- HHS is diagnosed with glucose usually >600 mg/dL, elevated serum osmolality (effective >300 or total >320 mOsm/kg), minimal ketosis, and pH >=7.3.
- Euglycemic DKA, linked to SGLT2 inhibitor use, can occur with blood glucose below 200 mg/dL, so ketone testing -- not glucose alone -- confirms the diagnosis.
- DKA occurs more often in type 1 diabetes and younger people, while HHS occurs more often in type 2 diabetes and older adults, with higher mortality.
- Sick-day rules direct people with diabetes to never stop basal/background insulin, check glucose and ketones frequently during illness, and stay hydrated.
Hyperglycemia
Hyperglycemia is elevated blood glucose above an individual's target range. It arises from insufficient insulin action relative to glucose load — from missed medication doses, illness, stress hormones, corticosteroid use, or excess carbohydrate intake. As glucose rises, it exceeds the kidney's reabsorption threshold and spills into the urine, pulling water with it through osmotic diuresis; this drives the classic symptoms of polyuria, polydipsia, and dehydration, alongside blurred vision, fatigue, headache, and slow wound healing. Marked hyperglycemia — generally above roughly 250 mg/dL, especially in someone with type 1 diabetes or on insulin — warrants ketone testing because it can signal the start of a hyperglycemic crisis. Left uncorrected, hyperglycemia can progress to one of two life-threatening emergencies: diabetic ketoacidosis (DKA) and the hyperglycemic hyperosmolar state (HHS).
DKA vs. HHS: Diagnostic Criteria
| Criterion | DKA | HHS |
|---|---|---|
| Blood glucose | Usually >250 mg/dL (current consensus criteria use ≥200 mg/dL, or any level with known diabetes, to also capture euglycemic DKA) | Usually >600 mg/dL |
| pH | <7.3 | ≥7.3 (absence of acidosis) |
| Bicarbonate | <18 mEq/L | ≥15 mEq/L (near-normal) |
| Ketones | Positive — beta-hydroxybutyrate ≥3.0 mmol/L; an elevated anion gap (>12 mmol/L) traditionally supports the diagnosis | Minimal to absent — beta-hydroxybutyrate <3.0 mmol/L |
| Serum osmolality | Variable | Elevated — effective osmolality >300 mOsm/kg or total >320 mOsm/kg |
| Onset | Rapid, over hours | Gradual, over days |
| Typically seen in | Type 1 diabetes (also type 2 during severe illness/stress) | Type 2 diabetes, especially older adults |
Point-of-care blood beta-hydroxybutyrate testing is now the preferred way to diagnose and monitor DKA; anion gap is a supportive but no longer first-line criterion. Clinically, DKA classically presents with rapid, deep Kussmaul breathing, fruity (acetone) breath odor, nausea, vomiting, and abdominal pain, while HHS presents more gradually with profound dehydration and neurologic changes — lethargy, confusion, focal deficits, or seizures — driven by extreme hyperosmolarity. Clinical overlap between DKA and HHS occurs in up to one-third of hyperglycemic crises, and HHS carries a higher mortality rate than DKA because of the degree of dehydration and the comorbidities common in the older adults it typically affects.
Emergency Treatment Overview
Both DKA and HHS are medical emergencies typically managed in an emergency department or intensive care setting, built on three coordinated pillars: IV fluid resuscitation to correct the profound dehydration driven by osmotic diuresis (more severe in HHS), IV insulin therapy to shut off ketone production and gradually lower glucose, and electrolyte monitoring and repletion, especially potassium — insulin drives potassium into cells, so serum potassium can fall sharply during treatment even if it started high. Glucose and, in DKA, ketones/anion gap are followed serially until resolution, and any precipitating cause (infection, missed insulin, new medication) is identified and treated. Correcting glucose too quickly, particularly in HHS, risks dangerous shifts in osmolality, so treatment is deliberately gradual and closely monitored.
Euglycemic DKA and SGLT2 Inhibitors
Euglycemic DKA — ketoacidosis with blood glucose below 200 mg/dL — occurs in roughly 10% of DKA presentations and is increasingly common with SGLT2 inhibitor use, in both type 1 diabetes (off-label) and type 2 diabetes, because these medications lower glucose independent of insulin (via urinary glucose excretion) and can mask the usual glucose warning sign. Anyone taking an SGLT2 inhibitor needs ketone testing whenever they feel unwell, even with a normal-looking glucose reading, because relying on glucose alone can delay recognition of a true emergency.
Precipitating Factors
DKA is most often precipitated by infection or illness, missed or inadequate insulin doses (including pump or infusion-site failure), new-onset type 1 diabetes, myocardial infarction or stroke, and SGLT2 inhibitor use during illness, fasting, surgery, or a very-low-carbohydrate diet. HHS is most often precipitated by infection (the leading cause), medication nonadherence, new-onset type 2 diabetes, and dehydration, along with medications such as glucocorticoids, diuretics, and antipsychotics; older adults with limited access to water, impaired thirst sensation, or cognitive impairment are at particular risk because reduced fluid intake allows hyperosmolarity to progress unchecked.
Sick-Day Rules and Prevention
- Never stop basal/background insulin, even when not eating — illness raises counter-regulatory hormones, so insulin needs typically increase, not decrease
- Check blood glucose every 2-4 hours during illness
- Check ketones (blood or urine) whenever glucose exceeds about 250 mg/dL, during illness, or with nausea/vomiting, especially for type 1 diabetes or insulin pump users
- Take supplemental rapid-acting insulin correction doses as directed by the individualized sick-day plan
- Stay hydrated with sugar-free fluids; if unable to eat normally, replace carbohydrate with small sips of juice or regular soda
- Avoid strenuous exercise when ketones are present, since exercising in this state can worsen ketosis rather than lower glucose
- Hold SGLT2 inhibitors during acute illness, prolonged fasting, or before surgery to reduce euglycemic DKA risk
- Keep a written sick-day plan developed with the care team, including emergency contact numbers and ketone-testing supplies
When to Seek Emergency Care
Seek immediate emergency care for persistent vomiting or inability to keep fluids down, moderate-to-large ketones that do not improve with correction doses and fluids, blood glucose that stays high despite repeated correction doses, rapid deep (Kussmaul) breathing or fruity-smelling breath, severe abdominal pain, signs of dehydration, or any confusion, extreme drowsiness, or altered mental status — these signal possible DKA or HHS and require prompt evaluation and treatment rather than continued home management.
A person with type 2 diabetes presents with blood glucose of 680 mg/dL, pH 7.35, serum bicarbonate 22 mEq/L, minimal ketones, and effective serum osmolality of 328 mOsm/kg. Which condition is this?
A person taking an SGLT2 inhibitor develops nausea and vomiting during a viral illness. Their blood glucose reads 175 mg/dL, which looks reassuring. What is the priority action?