Bedside Snapshot

Endogenous peptide hormone that promotes cellular uptake and storage of glucose, potassium, and other substrates. In critical care it's mainly used for: (1) DKA/HHS management, (2) IV insulin infusions for stress hyperglycemia, (3) rapid K⁺ shifting in hyperkalemia, and (4) high-dose insulin euglycemia therapy (HIET) in cardiogenic shock from calcium channel blocker (CCB) or beta-blocker overdose.

ICU glycemic targets: Major guidelines recommend starting or intensifying insulin for persistent glucose ≥180 mg/dL, aiming for a target range 140–180 mg/dL in most critically ill adults to balance control and hypoglycemia risk.

DKA (adult) – regular insulin IV: Common starting regimen is an infusion of 0.1 units/kg/hour (with or without a 0.1 units/kg IV bolus), titrated to drop glucose by about 50–70 mg/dL per hour while clearing ketoacidosis. HHS often uses 0.05 units/kg/hour due to greater osmotic shifts risk.

ICU insulin infusion for general hyperglycemia: Regular insulin is typically mixed as 1 unit/mL in 0.9% NaCl and run via infusion pump using weight-based or formula-based algorithms (e.g., starting around 1–3 units/hour and titrating hourly based on bedside glucose). Protocols differ by institution.

Hyperkalemia: Regular insulin 5–10 units IV bolus plus 25 g dextrose is standard to shift K⁺ intracellularly, lowering serum K⁺ by roughly 0.6–1.2 mEq/L within 15–30 minutes, with effect for 2–6 hours. Lower doses (e.g., 5 units) are increasingly used in renal failure to reduce hypoglycemia risk.

High-dose insulin euglycemia therapy (HIET): For CCB/β-blocker-induced cardiogenic shock, regular insulin is given as 1 unit/kg IV bolus, then infusion 0.5–1 units/kg/hour, titrated up to ~10 units/kg/hour with aggressive dextrose and electrolyte support. This improves inotropy and myocardial metabolism and is often more effective than vasopressors alone.

Major risks: Hypoglycemia (including delayed episodes after hyperkalemia or HIET therapy), hypokalemia, and fluid overload from dextrose support. HIET specifically requires continuous glucose, K⁺, and hemodynamic monitoring with protocolized titration.

Brand & Generic Names

Generic Name: Insulin (focus: regular insulin IV; brief notes on subcutaneous regimens)
Common Products (Acute Care Focus): Regular insulin (U-100; e.g., Humulin R, Novolin R) for IV infusions and boluses; rapid-acting analogs (lispro, aspart) and basal insulins (glargine, detemir, degludec, NPH) mainly for subcutaneous use

Medication Class

Peptide hormone; anabolic and antihyperglycemic agent; essential therapy in DKA/HHS; membrane Na⁺/K⁺-ATPase activator for hyperkalemia; high-dose inotrope/metabolic support in CCB/β-blocker toxicity

Pharmacology

Mechanism of Action (High-Yield for Critical Care):

Insulin binds to the insulin receptor (a transmembrane tyrosine kinase) on target cells, leading to autophosphorylation and activation of downstream signaling cascades (PI3K/Akt, MAPK)
Glucose metabolism: Promotes translocation of GLUT4 transporters to the cell membrane in skeletal muscle and adipose tissue, increasing glucose uptake; stimulates glycogenesis and lipogenesis while inhibiting gluconeogenesis, lipolysis, and ketogenesis
Potassium shift: Via Na⁺/K⁺-ATPase upregulation, insulin drives K⁺ into cells, acutely lowering serum K⁺. This is independent of its long-term metabolic effects and is the basis for hyperkalemia therapy
Myocardial effects in HIET: High-dose insulin improves cardiac myocyte carbohydrate utilization, promotes aerobic metabolism, enhances contractility, and improves vascular tone, thereby increasing cardiac output in CCB/β-blocker toxicity
Anabolic effects: Promotes protein synthesis, nucleic acid synthesis, and inhibits proteolysis; in hypercatabolic states (sepsis, trauma) insulin helps shift metabolism toward anabolic or at least less catabolic pathways while controlling glucose

Pharmacokinetics – Regular Insulin in ICU/ED:

Formulation: Human regular insulin U-100 (100 units/mL) in multidose vials or cartridges. For IV infusion, it is typically diluted in 0.9% NaCl to 1 unit/mL (e.g., 100 units in 100 mL NS, or 250 units in 250 mL NS) and run via infusion pump
Onset (IV): Essentially immediate distribution phase; onset of glucose-lowering effect within minutes, with very short distribution half-life
Duration (IV): After a change in infusion rate, steady-state effect is typically reached within 30–60 minutes; after stopping an infusion, effect largely dissipates over 30–60 minutes for moderate doses
Onset (subcutaneous regular insulin): ~30 minutes, peak 2–4 hours, duration 6–8 hours (longer in renal impairment or low perfusion). Rapid analogs (lispro/aspart/glulisine) have faster onset (10–20 minutes) and shorter duration (~3–5 hours)
Metabolism: Degraded primarily by insulinases in liver, kidney, and muscle; small amount renally excreted unchanged
Renal impairment: Decreased insulin clearance can prolong effect and increase risk of hypoglycemia; infusion protocols in CKD/ESRD often use lower starting rates and slower titration
Hepatic impairment: Reduced gluconeogenesis and glycogen stores may increase hypoglycemia risk even at modest insulin doses; close glucose monitoring and conservative dosing are required

Dosing & Administration

Medication Forms & ICU/ED Preparations:

Regular insulin U-100 vials (100 units/mL): Most common ICU/ED source for IV infusions and boluses. Always verify concentration and use a dedicated infusion pump for continuous drips
Standard ICU infusion mix: 1 unit/mL regular insulin in 0.9% NaCl (e.g., 100 units in 100 mL or 250 units in 250 mL). HIET may require more concentrated solutions (e.g., 10 units/mL) to avoid excessive volumes
Subcutaneous regimens: Rapid-acting analogs (lispro, aspart, glulisine) for prandial and correctional dosing; basal insulins (glargine, detemir, degludec, NPH) for background coverage when transitioning off drips or in stable inpatients
Insulin should be administered in-line alone when possible (avoid co-infusion with incompatible drugs); use dedicated line for HIET if feasible

Dosing – Key ICU/ED Scenarios (Regular Insulin):

Indication / Scenario	Typical Starting Dose	Titration / Targets	Notes
DKA – adult (IV regular insulin)	0.1 units/kg/hour IV infusion (with or without 0.1 units/kg IV bolus)	Aim for glucose fall ~50–70 mg/dL/hour and closure of anion gap	Bolus often omitted if adequate perfusion; adjust rate if glucose not falling or anion gap not closing
HHS – adult (IV regular insulin)	0.05 units/kg/hour IV infusion	Aim for glucose fall ~40–80 mg/dL/hour	Start after initial fluid resuscitation; slower correction to avoid rapid osmotic shifts
General ICU hyperglycemia (non-DKA/HHS)	Regular insulin infusion ~1–3 units/hour IV (≈0.02–0.05 units/kg/hour)	Titrate hourly to maintain glucose 140–180 mg/dL	Specific algorithm varies by institution (weight-based or formula-based)
Hyperkalemia – adult (K⁺ shift)	5–10 units regular insulin IV bolus + 25 g dextrose IV (e.g., 50 mL D50W)	Monitor glucose every 30–60 minutes for at least 4–6 hours	Consider 5 units in ESRD/elderly to reduce hypoglycemia risk; give dextrose unless marked hyperglycemia
High-dose insulin euglycemia therapy (HIET) – adult	1 units/kg IV bolus, then 0.5–1 units/kg/hour infusion	Titrate up by ~0.5–1 units/kg/hour to max ~10 units/kg/hour based on hemodynamic response	Requires dextrose infusion, frequent glucose and K⁺ checks, and invasive hemodynamic monitoring
Hypertriglyceridemic pancreatitis (example regimen)	0.05–0.1 units/kg/hour IV regular insulin	Titrate dextrose to maintain glucose ~120–180 mg/dL	Institution-specific; used to enhance lipoprotein lipase and reduce triglycerides

Additional Dosing & Titration Notes:

Always use a standardized institutional protocol for IV insulin infusions in ICU/ED; these are complex and require frequent bedside glucose checks (often every hour initially)
For DKA, insulin therapy is aimed at closing the anion gap and resolving ketoacidosis, not just normalizing glucose. When glucose falls below ~200–250 mg/dL, dextrose is added while continuing insulin until the gap closes
In HHS, aggressive fluid resuscitation is usually prioritized before starting insulin; insulin is started at lower rates to avoid overly rapid osmolar shifts that can precipitate cerebral edema
For HIET, be prepared for massive dextrose requirements (e.g., D10–D20 infusions) and frequent electrolyte replacement, especially potassium and occasionally magnesium and phosphate
Avoid abrupt discontinuation of insulin infusions in insulin-dependent diabetics or those recovering from DKA/HHS; overlap with subcutaneous basal insulin (e.g., give basal 2–4 hours before stopping drip) to prevent rebound hyperglycemia and ketoacidosis

Contraindications

Absolute/Relative Contraindications (For IV Insulin as a Drug):

There are no absolute contraindications in life-threatening hyperglycemia, DKA/HHS, hyperkalemia, or CCB/β-blocker cardiogenic shock when insulin is indicated
True insulin allergy is rare but possible; desensitization or alternative preparations (e.g., human vs analog) may be needed in non-emergent settings

Major Precautions:

Hypoglycemia: The main acute risk. Requires protocolized glucose monitoring (hourly or more often when changing rates) and prompt dextrose rescue for low values
Renal impairment: Reduced insulin clearance increases hypoglycemia risk; lower initial doses and slower titration are often warranted, particularly for non-DKA indications
Hepatic impairment, malnutrition, or sepsis: Diminished glycogen stores and impaired gluconeogenesis predispose to hypoglycemia; liberal dextrose support may be necessary
Electrolyte shifts: Insulin causes intracellular K⁺ and phosphate shifts; monitor and replace potassium, phosphate, and magnesium as needed, especially during DKA/HHS or HIET
Volume status: Dextrose infusions required for HIET and hypoglycemia prevention can contribute to fluid overload; consider concentrated dextrose solutions via central access in volume-sensitive patients
Concomitant dextrose-lowering agents (e.g., sulfonylureas, SGLT2 inhibitors) or impaired counterregulatory responses (adrenal insufficiency, autonomic neuropathy) may exacerbate hypoglycemia risk

Adverse Effects

Common:

Hypoglycemia (sweating, tachycardia, tremor, confusion)
Injection site issues (for subcutaneous use): lipodystrophy, local irritation
Mild hypokalemia and hypophosphatemia with ongoing infusions

Serious:

Severe hypoglycemia leading to seizures, coma, or neurologic injury if not recognized and treated promptly
Profound hypokalemia, particularly in combination with other K⁺-shifting therapies (beta-agonists, bicarbonate) or dialysis
Cerebral edema in DKA/HHS if glucose/osmolality corrected too rapidly (multifactorial, not insulin alone but linked to overly aggressive therapy)
Rebound hyperglycemia or recurrence of ketoacidosis if insulin is stopped too early or basal coverage is inadequate in insulin-dependent patients

Monitoring

Bedside capillary or arterial/venous plasma glucose: At least hourly during IV insulin titration; every 15–30 minutes after rate changes in unstable patients or during HIET
Serum electrolytes (K⁺, Na⁺, Cl⁻, HCO₃⁻, Mg²⁺, PO₄³⁻) and BUN/creatinine every 2–4 hours in DKA/HHS and HIET until stable
Anion gap, β-hydroxybutyrate (if available), and venous blood gases in DKA to assess resolution of ketoacidosis
Hemodynamics, urine output, and lactate in HIET and hyperglycemic emergencies, particularly when insulin is being used in shock states
For subcutaneous regimens: pre-meal and bedtime glucose in stable inpatients; more frequent checks during changes in nutrition, steroids, or infection status

Standard ICU/ED Indications (Focus on IV Regular Insulin)

Diabetic ketoacidosis (DKA) – adult and pediatric: Continuous IV regular insulin infusion to suppress ketogenesis, correct hyperglycemia, and close the anion gap, alongside fluids and electrolytes
Hyperosmolar hyperglycemic state (HHS): Lower-dose IV insulin infusion to gradually decrease severe hyperglycemia and hyperosmolarity after initial fluid resuscitation
Stress hyperglycemia in critically ill patients (sepsis, post-op, trauma, neuro ICU): IV insulin infusion targeting glucose 140–180 mg/dL when persistent hyperglycemia ≥180 mg/dL is present
Hyperkalemia: IV regular insulin bolus with IV dextrose to acutely shift potassium intracellularly in life-threatening or significant hyperkalemia
High-dose insulin euglycemia therapy (HIET): CCB/β-blocker overdose with cardiogenic shock or refractory hypotension; insulin used as an inotropic/metabolic support agent with concurrent dextrose and electrolyte management
Hypertriglyceridemic pancreatitis: Insulin infusion (often 0.05–0.1 units/kg/hour) used to enhance lipoprotein lipase activity and lower triglycerides, typically in combination with dextrose to maintain euglycemia (institution-specific practice)

Clinical Pearls

DKA: Don't chase the glucose alone: In DKA, insulin's primary job is to shut down ketogenesis and close the anion gap; once glucose is ~200–250 mg/dL, add dextrose and continue insulin at a lower rate until the gap is closed.

Hyperkalemia K⁺-lowering is temporary: For hyperkalemia, insulin's K⁺-lowering effect lasts only a few hours and does nothing to remove total body potassium – always pair with definitive therapy (binders, diuretics, dialysis) as appropriate.

HIET is an inotrope, not just glucose control: When using HIET, think of insulin as a high-dose inotrope/metabolic modulator, not just a glucose drug – and treat glucose and K⁺ as continuous drips in their own right, not afterthoughts.

Prime the IV line: To reduce insulin adsorption to IV tubing (especially at very low rates), many protocols prime the line with insulin-containing solution before starting the infusion.

Never stop insulin abruptly in DKA/HHS: Never discontinue an insulin infusion in a known insulin-dependent diabetic or recent DKA/HHS patient without giving basal insulin and confirming that they are tolerating a subcutaneous regimen; otherwise, ketoacidosis can recur quickly.

References

American Diabetes Association. (2025). 16. Diabetes care in the hospital: Standards of Medical Care in Diabetes—2025. Diabetes Care.
Dhatariya, K. K., Corsino, L., Umpierrez, G. E., et al. (2020). Management of diabetes and hyperglycemia in hospitalized patients. In Endotext [Internet]. MDText.com, Inc.
Weingart, S. (2025). Glucose control (IBCC), Diabetic ketoacidosis (IBCC), Hyperosmolar hyperglycemic state (IBCC), Hyperkalemia (IBCC). EMCrit Project. https://emcrit.org/ibcc/
Engebretsen, K. M., Kaczmarek, K. M., Morgan, J., & Holger, J. S. (2011). High-dose insulin therapy in beta-blocker and calcium channel-blocker poisoning. Clinical Toxicology, 49(4), 277–283.
Moussavi, K., et al. (2020). Comparison of IV insulin dosing strategies for hyperkalemia. Critical Care Explorations, 2(4), e0087.

Insulin (ICU/ED)