Bit · Endo
DKA vs HHS
Two hyperglycemic emergencies. DKA = insulin is absent, ketones are the headline. HHS = insulin is just low enough to stop fat breakdown but not enough to control glucose — so glucose runs to 1000+ and the patient dries out.
Mechanism
Both start with too little insulin and too much glucose. The pivot is whether there is enough insulin to suppress lipolysis:
- DKA — almost no insulin. Adipose tissue runs free, releases free fatty acids, liver makes ketone bodies. Anion gap acidosis. Glucose typically 400–800.
- HHS — small amount of insulin remains. Lipolysis stays suppressed, so no ketones. But the residual insulin can't keep up with glucose — osmotic diuresis ramps for days. Glucose >600, often >1000. Patient is profoundly dehydrated and altered.
Differentiator Table
| DKA | HHS | |
| Typical patient | T1DM (or new dx) | Older T2DM |
| Glucose | 400–800 mg/dL | >600, often >1000 |
| Ketones | ↑↑ (β-hydroxybutyrate) | Minimal / absent |
| Arterial pH | <7.30 | ≥7.30 |
| Anion gap | ↑↑ | Normal or mildly ↑ |
| Serum osm | <320 mOsm/kg | >320 mOsm/kg |
| Mental status | Variable | Stupor / coma (osm-driven) |
| Onset | Hours to a day | Days |
| First-line tx | IV fluids → insulin drip → K⁺ replacement | IV fluids (huge volume) → insulin drip → K⁺ |
The Pivot
Two numbers decide it:
- pH below 7.30 with ketones? → DKA.
- Glucose >600 with serum osm >320 and minimal/no ketones? → HHS.
Patient can have features of both ('mixed') — treat as the more severe of the two.
NBME-Style Stem
A 72-year-old woman with type 2 diabetes is brought in obtunded. She was last seen well 3 days ago. Glucose 1180 mg/dL, Na⁺ 152 mEq/L (corrected), bicarbonate 22 mEq/L, arterial pH 7.34, ketones trace, serum osm 348 mOsm/kg. Which of the following is the most appropriate initial step?
Concept Anchor
DKA and HHS are the same disease at different insulin levels — drop insulin to zero and you light up the ketone factory (DKA); leave a trickle of insulin and you suppress ketones but glucose runs the patient dry over days (HHS).