HHS vs DKA: Signs and Diagnostic Differences

Hyperosmolar hyperglycemic state (HHS) and diabetic ketoacidosis (DKA) are serious diabetes-related emergencies caused by insufficient effective insulin. HHS usually causes profound dehydration and very high glucose with little ketoacidosis, while DKA causes significant ketone production and metabolic acidosis; the two conditions can overlap.

HHS Clinical Manifestations and Diagnostic Criteria vs DKA: At a Glance

HHS (hyperosmolar hyperglycemic state) and DKA (diabetic ketoacidosis) are acute complications of diabetes in which the body cannot use glucose effectively. Both can lead to dangerous dehydration and require urgent hospital treatment. The central distinction is that DKA involves substantial ketone production and blood acidity, while HHS involves more extreme hyperglycemia and hyperosmolality, usually with minimal ketosis or acidosis.

They are not always completely separate conditions. Some people have features of both, particularly severe high glucose with elevated ketones and acidosis. Clinicians therefore assess symptoms, examination findings and multiple laboratory results together rather than relying on one value alone.

Feature	DKA	HHS
Typical diabetes setting	More common in type 1 diabetes, but can occur in type 2 diabetes	More common in type 2 diabetes, especially in older adults, but can occur in other forms of diabetes
Usual onset	Hours to about 1 day	Days to weeks
Blood glucose	Usually at least 200 mg/dL (11.1 mmol/L), though it may be higher	Usually 600 mg/dL (33.3 mmol/L) or higher
Ketones	Clearly elevated	Absent or mildly elevated
Acid-base status	Metabolic acidosis is present	Usually no significant acidosis
Dehydration and osmolality	Present, variable severity	Often profound, with high serum osmolality
Common clinical pattern	Nausea, vomiting, abdominal pain, deep breathing	Marked thirst, weakness, confusion or reduced alertness

Clinical Manifestations: How HHS and DKA May Feel

Both conditions can cause intense thirst, frequent urination, dry mouth, fatigue, blurred vision and progressive dehydration. As dehydration worsens, a person may have dizziness, weakness, low blood pressure, a fast heartbeat or reduced urine output. Illness, infection or missed diabetes treatment may be present in the days before symptoms become severe.

DKA commonly produces nausea, vomiting and abdominal discomfort. The body attempts to compensate for acid buildup through deep, labored or rapid breathing, sometimes called Kussmaul breathing. A fruity or acetone-like breath odor can occur because of ketones, but it is not present in every case and should never be used as a home diagnostic test.

In HHS, severe fluid loss and high osmolality often have a stronger effect on brain function. Confusion, drowsiness, altered behavior, weakness, seizures or coma can occur, especially when illness has progressed without treatment. These symptoms can also arise in DKA, so mental status changes always need emergency evaluation.

How to Determine HHS vs DKA?

A clinician distinguishes HHS from DKA by combining the history and physical examination with urgent blood and urine testing. Important tests include plasma glucose, beta-hydroxybutyrate (the principal blood ketone), electrolytes, bicarbonate, blood pH, kidney function and measured or calculated serum osmolality. The clinical team also checks for triggers such as infection, heart attack, stroke, pancreatitis, medication effects or problems with insulin delivery.

DKA is favored when ketones are significantly elevated and there is metabolic acidosis, shown by a low bicarbonate level and low pH. HHS is favored when glucose and serum osmolality are markedly high, dehydration is substantial and ketosis or acidosis is absent or limited. A high anion gap supports ketoacidosis, but results must be interpreted in context because other illnesses can also affect acid-base balance.

It is important not to self-diagnose based on a glucose reading alone. A high reading can occur without DKA or HHS, and DKA can occasionally occur at lower glucose levels, including in people taking certain diabetes medicines such as SGLT2 inhibitors. Emergency clinicians use repeat tests and close monitoring because the situation can change during treatment.

What Are the Differences in Lab Values Between DKA and HHS?

In DKA, current consensus criteria generally include diabetes or hyperglycemia, significant ketonemia and metabolic acidosis. Blood glucose is often 200 mg/dL (11.1 mmol/L) or above, although glucose can be lower in euglycemic DKA. Beta-hydroxybutyrate is typically 3.0 mmol/L or higher, while bicarbonate is below 18 mmol/L and venous or arterial pH is below 7.30. The anion gap is commonly increased.

In HHS, plasma glucose is typically 600 mg/dL (33.3 mmol/L) or above and effective serum osmolality is generally above 300 mOsm/kg, or total serum osmolality above 320 mOsm/kg, depending on the criterion used. Significant ketonemia is not expected: beta-hydroxybutyrate is usually below 3.0 mmol/L. Bicarbonate is generally 15 mmol/L or higher, and pH is usually 7.30 or higher.

These thresholds are clinical guides rather than a substitute for professional assessment. Kidney impairment, dehydration, infection, vomiting, pregnancy and medicines can influence glucose, electrolyte and acid-base results. Potassium deserves particular attention: total body potassium may be depleted even when the initial blood potassium level appears normal or high.

• DKA pattern: elevated ketones plus acidosis.
• HHS pattern: extreme hyperglycemia plus hyperosmolality, with little or no acidosis.
• Mixed pattern: high osmolality alongside meaningful ketosis and acidosis.

What Are the Criteria for Diagnosing DKA and HHS?

Diagnostic criteria are based on international expert guidance and may be adapted slightly by local hospitals. For DKA, clinicians look for all three core components: diabetes or hyperglycemia, elevated ketones and metabolic acidosis. Severity is then assessed using pH, bicarbonate, ketone level and mental status, which helps guide the location and intensity of monitoring.

For HHS, the main components are severe hyperglycemia, hyperosmolality, limited ketone elevation and no clinically important metabolic acidosis. Mental status changes may be present, but they are no longer considered essential for diagnosis because HHS can be diagnosed before confusion develops. Clinicians also evaluate dehydration, circulation, kidney function and possible complications.

Both DKA and HHS should prompt a search for the underlying cause. Common triggers include missed or insufficient insulin, newly diagnosed diabetes, infection, surgery, trauma, heart attack, stroke, pancreatitis and some medicines. Addressing the trigger is an essential part of preventing recurrence. For broader information about diabetes types and long-term management, see diabetes.

What Are the Three Diagnostic Criteria for DKA?

The three diagnostic criteria for DKA are: first, diabetes or hyperglycemia; second, elevated ketones in the blood or urine, preferably measured as blood beta-hydroxybutyrate; and third, metabolic acidosis. Metabolic acidosis is identified through a low blood pH and/or low serum bicarbonate, with clinical interpretation of the full acid-base picture.

In practical terms, many current criteria use glucose of at least 200 mg/dL (11.1 mmol/L) or known diabetes, beta-hydroxybutyrate of at least 3.0 mmol/L or urine ketones of 2+ or more, and pH below 7.30 and/or bicarbonate below 18 mmol/L. Urine ketone testing can be useful, but blood beta-hydroxybutyrate more directly reflects the ketone responsible for DKA and is preferred when available.

DKA can be mild, moderate or severe. This classification is based largely on the degree of acidosis, ketone elevation and changes in alertness rather than glucose alone. Prompt treatment helps correct dehydration, insulin deficiency, electrolyte disturbances and the cause of the episode.

What to Do for Each Case: Treatment and Recovery

Suspected DKA or HHS should be treated in an emergency department or hospital, not at home. Treatment begins with carefully selected intravenous fluids, frequent checks of blood glucose and electrolytes, and insulin when it is safe to start. Potassium and other electrolytes are managed closely because treatment can shift them rapidly and affect heart and muscle function.

DKA treatment aims to stop ketone production, correct acidosis and restore fluid and electrolyte balance. HHS treatment prioritizes gradual restoration of circulation and hydration while glucose and osmolality are lowered safely. In both conditions, clinicians avoid overly rapid shifts in glucose or osmolality and adjust treatment based on repeat laboratory tests, urine output, heart and kidney health, and neurological status.

After recovery, the care plan may include diabetes education, review of insulin technique or medicines, sick-day guidance and follow-up testing. A clinician may advise when to check glucose and ketones during illness and when to temporarily seek medical advice about diabetes medicines. Acıbadem Health Point’s multidisciplinary specialists and JCI-accredited hospitals diagnose and treat diabetes emergencies for international patients.

When to Seek Medical Care

Emergency medical care is needed for a person with diabetes who has repeated vomiting, severe abdominal pain, deep or difficult breathing, confusion, fainting, seizures, inability to keep fluids down, signs of severe dehydration or very high glucose with worsening symptoms. These signs may indicate DKA, HHS or another urgent illness and should not be managed by waiting for symptoms to pass.

People who are unwell with diabetes should follow their individualized sick-day plan and contact their diabetes team promptly if glucose remains high, ketones are present, or insulin cannot be taken as prescribed. Anyone with new symptoms of diabetes, such as marked thirst, frequent urination and unexplained weakness, should arrange timely medical assessment before an emergency develops.

Family members and caregivers should seek urgent help if a person becomes unusually sleepy, confused or difficult to wake. Bringing available information about diabetes medicines, insulin use, recent glucose or ketone results and recent illnesses can help the emergency team begin care efficiently.

Frequently asked questions