Situation: A 76-year-old woman with type 2 diabetes mellitus is brought from home after three days of increasing drowsiness and poor oral intake during a febrile illness. She weighs 60 kg. The provider diagnoses hyperosmolar hyperglycemic state (HHS). Under the 2024 international consensus on hyperglycemic crises, what is the usual starting rate of the intravenous (IV) regular insulin infusion in HHS?

The consensus starts IV insulin at 0.05 units/kg/h in HHS, half the 0.1 units/kg/h used in DKA, because glucose in HHS is lowered gradually to reduce the risk of cerebral edema and because fluids alone already lower glucose substantially.

Why the infusion starts low in HHS

In hyperosmolar hyperglycemic state, the primary physiologic problem is profound water deficit and hyperosmolality, not ketoacidosis. Because the patient still has some endogenous insulin secretion, fluid replacement alone lowers serum glucose substantially before exogenous insulin is even added. Starting insulin at the same rate used for diabetic ketoacidosis would therefore overshoot and drop glucose too quickly. The 2024 international consensus recommendation is to begin regular insulin at 0.05 units/kg/h in HHS, which is half the 0.1 units/kg/h commonly used in DKA .

Parameter	HHS	DKA
Usual starting IV regular insulin	0.05 units/kg/h	0.1 units/kg/h
Primary defect	Water deficit and hyperosmolality	Insulin deficiency with ketoacidosis
Response to fluids alone	Glucose falls markedly	Glucose falls less markedly
Main risk with rapid insulin	Cerebral edema from osmotic shifts	Hypokalemia and cerebral edema

Why gradual glucose lowering matters

HHS develops over days to weeks, allowing brain cells to generate idiogenic osmoles that protect intracellular volume against the high extracellular osmolality. If serum glucose is corrected too rapidly, water shifts into brain cells faster than those osmoles can be cleared, producing cerebral edema. A low initial insulin infusion rate, combined with aggressive isotonic fluid resuscitation, permits a controlled decline in glucose and osmolality .

Key point! In HHS, insulin is not the first priority. Fluid resuscitation is started first, and insulin is typically withheld until glucose stops falling with fluids alone or until potassium is confirmed adequate. When insulin is started, the low rate of 0.05 units/kg/h reflects the principle of gradual correction .

Watch out! Do not confuse the HHS insulin starting rate with the DKA rate. A patient with mixed DKA/HHS features may require individualized dosing, but for pure HHS the consensus default is the lower rate .

Clinical application for this patient

This 76-year-old, 60 kg woman has type 2 diabetes and a three-day history of drowsiness and poor oral intake during a febrile illness. Her presentation is consistent with insidious dehydration, hyperglycemia, and hyperosmolality rather than abrupt ketoacidosis. At 0.05 units/kg/h, her initial infusion would be 3 units/h. The priority is to restore intravascular volume with isotonic crystalloid while monitoring glucose, osmolality, electrolytes, and mental status. Insulin is titrated only after the initial fluid-driven decline in glucose plateaus, and the goal is a controlled reduction rather than rapid normalization .

Why the other options are incorrect

0.02 units/kg/h is lower than the consensus starting dose and would unnecessarily delay glucose control once fluids alone are no longer lowering glucose. 0.1 units/kg/h is the DKA starting rate and is too aggressive for most HHS patients because it increases the risk of overly rapid osmotic shifts. 0.14 units/kg/h exceeds even the DKA rate and has no role as an initial infusion in hyperglycemic crises. The distinction matters because HHS mortality remains high, and avoidable complications such as cerebral edema and electrolyte derangements are directly tied to the speed of correction .