DKA vs HHS
How to tell DKA and HHS apart when a board question makes them look alike.
Step 2 CK pairs are in open beta while clinical review finishes. Spot an issue? Tell us.
Marked anion gap acidosis with ketonemia is the key discriminator for DKA.
Side by side
Anion gap metabolic acidosis with positive serum ketones and bicarbonate below 18 mEq/L indicates DKA.
Severe hyperglycemia with effective serum osmolality above 320 mOsm/kg and minimal ketosis indicates HHS.
Near-complete insulin deficiency drives lipolysis and ketoacid production.
Relative insulin deficiency limits ketogenesis but allows profound hyperglycemia and osmotic dehydration.
DKA typically has glucose above 250 mg/dL, arterial pH below 7.30, bicarbonate below 18 mEq/L, and anion gap above 12 with positive beta-hydroxybutyrate.
HHS usually has glucose above 600 mg/dL, osmolality above 320 mOsm/kg, pH above 7.30, bicarbonate above 18 mEq/L, and little or no ketonemia.
The trap
Anchoring on glucose level alone leads to misclassification, especially when DKA is euglycemic on SGLT2 inhibitors. Acid-base status and ketones determine the diagnosis and insulin-potassium sequence.
The repair move
Next best step: give 0.9% saline 1 to 1.5 liters in the first hour, check potassium, replete potassium before insulin if K+ is below 3.3 mEq/L, then start IV regular insulin at 0.1 units/kg/hour and close the anion gap before transitioning to subcutaneous insulin. In HHS, prioritize aggressive fluids first and correct osmolality gradually.
Try a free question
CoreA 20-year-old with diabetes has glucose 420 mg/dL, pH 7.14, bicarbonate 9 mEq/L, and potassium 2.9 mEq/L. What is the next best step in management?
Show answer and explanation
Answer: B. Give IV potassium replacement before insulin. Severe hypokalemia must be corrected before insulin to prevent life-threatening arrhythmias.
Why the other choices are tempting
- A. Wrong. Immediate insulin with potassium below 3.3 mEq/L is unsafe.
- C. Wrong. Bicarbonate is reserved for extreme acidemia and is not routine first-line.
- D. Wrong. Oral agents are inappropriate in acute DKA.
- E. Wrong. This metabolic emergency requires inpatient intensive treatment.
Flashcards
Tap a card to flip it.
Which laboratory pattern confirms DKA rather than HHS?
Anion gap metabolic acidosis with ketonemia and low bicarbonate.
What threshold defines severe hyperosmolarity in HHS?
Effective serum osmolality greater than 320 mOsm/kg.
Quick answers
What is the fastest way to tell DKA from HHS?
Marked anion gap acidosis with ketonemia is the key discriminator for DKA.
What is the key clue for DKA?
Anion gap metabolic acidosis with positive serum ketones and bicarbonate below 18 mEq/L indicates DKA.
What is the key clue for HHS?
Severe hyperglycemia with effective serum osmolality above 320 mOsm/kg and minimal ketosis indicates HHS.
What is the common trap with DKA vs HHS?
Anchoring on glucose level alone leads to misclassification, especially when DKA is euglycemic on SGLT2 inhibitors. Acid-base status and ketones determine the diagnosis and insulin-potassium sequence.