DKA vs HHS
How to tell DKA and HHS apart when a board question makes them look alike.
DKA is ketotic anion-gap acidosis; HHS is hyperosmolar dehydration with absent or mild ketones and little acidosis.
Side by side
Ketones, anion gap metabolic acidosis, abdominal pain, Kussmaul respirations, and dehydration.
Extreme hyperglycemia, hyperosmolality, altered mental status, and absent or mild ketones.
Severe insulin deficiency triggers lipolysis and ketone production.
Enough insulin remains to suppress ketogenesis but not enough to control glucose.
Low bicarbonate, low pH, ketonemia, and anion gap point to DKA.
Very high glucose and serum osmolality with little acidosis point to HHS.
The trap
Glucose level alone does not pick the diagnosis. DKA can present with glucose as low as 250 mg/dL (especially euglycemic DKA on SGLT2 inhibitors), while HHS often runs above 1000 mg/dL. The deciding axis is the ketone and acid-base profile. DKA has pH below 7.30, bicarbonate under 18 mEq/L, an anion gap above 12, positive serum and urine ketones, and Kussmaul respirations in a younger type 1 diabetic. HHS has pH above 7.30, bicarbonate above 18 mEq/L, minimal or absent ketones, but serum osmolality above 320 mOsm/kg driving altered mental status in an older type 2 diabetic. Both need IV normal saline 1 to 2 L first, then insulin and aggressive potassium replacement because insulin drives potassium into cells and total body potassium is depleted even when serum potassium looks normal.
Watch it explained
The repair move
Read the pH, bicarbonate, anion gap, and ketone line before reacting to the glucose value.
Try a free question
CoreA young patient with type 1 diabetes has abdominal pain, vomiting, Kussmaul respirations, positive serum ketones, and anion gap metabolic acidosis. Which diagnosis is most likely?
Show answer and explanation
Answer: A. DKA. Ketones plus anion gap acidosis and Kussmaul respirations point to DKA.
Why the other choices are tempting
- B. HHS has extreme hyperglycemia and hyperosmolality with absent or mild ketones.
- C. Lactic acidosis does not produce ketonemia as the key feature.
- D. SIADH causes hyponatremia from water retention.
- E. DI causes dilute polyuria and hypernatremia.
Flashcards
Tap a card to flip it.
What acid-base pattern separates DKA from HHS?
DKA has anion-gap metabolic acidosis with low bicarbonate and ketones; HHS has little acidosis.
Why are ketones prominent in DKA?
Severe insulin deficiency permits lipolysis and hepatic ketone production.
Quick answers
What is the fastest way to tell DKA from HHS?
DKA is ketotic anion-gap acidosis; HHS is hyperosmolar dehydration with absent or mild ketones and little acidosis.
What is the key clue for DKA?
Ketones, anion gap metabolic acidosis, abdominal pain, Kussmaul respirations, and dehydration.
What is the key clue for HHS?
Extreme hyperglycemia, hyperosmolality, altered mental status, and absent or mild ketones.
What is the common trap with DKA vs HHS?
Glucose level alone does not pick the diagnosis. DKA can present with glucose as low as 250 mg/dL (especially euglycemic DKA on SGLT2 inhibitors), while HHS often runs above 1000 mg/dL. The deciding axis is the ketone and acid-base profile. DKA has pH below 7.30, bicarbonate under 18 mEq/L, an anion gap above 12, positive serum and urine ketones, and Kussmaul respirations in a younger type 1 diabetic. HHS has pH above 7.30, bicarbonate above 18 mEq/L, minimal or absent ketones, but serum osmolality above 320 mOsm/kg driving altered mental status in an older type 2 diabetic. Both need IV normal saline 1 to 2 L first, then insulin and aggressive potassium replacement because insulin drives potassium into cells and total body potassium is depleted even when serum potassium looks normal.