Which statement best differentiates DKA from HHS?

• A. DKA presents with ketoacidosis and anion gap metabolic acidosis, while HHS shows marked hyperglycemia with high osmolality and minimal ketosis.
• B. HHS presents with ketoacidosis with anion gap metabolic acidosis, whereas DKA shows high osmolality and minimal ketosis.
• C. DKA and HHS both have ketoacidosis, but HHS lacks acidosis.
• D. DKA has high osmolality with little ketosis; HHS has ketoacidosis with acidosis.

Answer: (A)

The distinguishing idea is how ketosis and acid-base status differ from osmolality in these two emergencies. Diabetic ketoacidosis arises from a severe lack of insulin that triggers lipolysis and production of ketone bodies, leading to ketoacidosis with an elevated anion gap metabolic acidosis (low pH, low bicarbonate). In hyperosmolar hyperglycemic state, there is enough insulin to inhibit substantial ketogenesis, but not enough to curb glucose, so you get very high blood glucose and a high serum osmolality with little or no ketosis and usually normal or near-normal pH and bicarbonate.

So the best way to differentiate is that DKA features ketoacidosis with anion-gap acidosis, while HHS shows marked hyperglycemia with high osmolality and minimal ketosis.