How should insulin be managed in a patient who is nil per os (NPO)?

Insulin Management in NPO Patients

For patients who are NPO, continue basal insulin at 60-80% of the usual dose and monitor blood glucose every 4-6 hours with correction insulin as needed. 1, 2

Core Management Strategy

A basal plus correction insulin regimen is the preferred treatment for noncritically ill hospitalized patients who are NPO. 1, 2 This approach maintains baseline insulin coverage while preventing dangerous hyperglycemia and metabolic decompensation that occurs when basal insulin is discontinued. 2

Specific Dosing Recommendations

• Reduce basal insulin to 60-80% of the home dose when the patient becomes NPO 1, 2
• For patients on long-acting analogs (glargine, degludec, detemir), administer 60-80% of the usual dose 1
• For patients on NPH insulin, give half of the usual dose 1
• Monitor blood glucose every 4-6 hours while NPO status continues 1, 2
• Add short-acting or rapid-acting correction insulin for hyperglycemia based on monitoring results 1, 2

Target Glucose Range

• Maintain blood glucose between 80-180 mg/dL in the perioperative and NPO setting 1
• Tighter glycemic control does not improve outcomes and increases hypoglycemia risk 1

Critical Pitfalls to Avoid

Never discontinue basal insulin completely when a patient is NPO - this leads to significant hyperglycemia and metabolic decompensation. 2 The "hold-the-insulin" routine is dangerous and reflects misunderstanding of the body's basal insulin needs. 3

Never rely solely on sliding scale insulin (SSI) without basal coverage - SSI as the sole method of insulin treatment is strongly discouraged in hospitalized patients. 1, 2 This reactive approach leads to poor glycemic control and rapid glucose fluctuations. 2

Evidence Quality and Nuances

The American Diabetes Association guidelines consistently recommend this approach across multiple years (2015,2018,2019), demonstrating strong consensus. 1, 2 A 2020 retrospective study of 258 patients found no difference in hypoglycemia rates between those receiving ≤50% versus >50% of home basal insulin, though the lower dose group had higher rates of hyperglycemia (97.6% vs 89%). 4 This suggests that while dose reduction prevents hypoglycemia, excessive reduction (below 50%) may lead to inadequate glycemic control.

Recent automated insulin algorithms have shown promise in NPO patients, with lower rates of both hypoglycemia (0.65% vs 1.10%) and severe hyperglycemia (5.40% vs 6.65%) compared to conventional physician-driven dosing. 5, 6

Special Populations

Type 1 Diabetes Patients

• Must continue basal insulin even when NPO to prevent diabetic ketoacidosis 1
• If DKA develops and resolves while patient remains NPO, continue intravenous insulin and fluid replacement with overlap when transitioning to subcutaneous insulin 1, 7

Patients on Enteral/Parenteral Nutrition Who Become NPO

• Continue prior basal insulin dose or calculate from total daily dose (usually 30-50% of total daily dose) 1, 2
• If no prior basal insulin, consider 5 units NPH/detemir every 12 hours or 10 units glargine every 24 hours 1

Patients with Renal or Hepatic Disease

• Monitor more closely for hypoglycemia as these conditions increase hypoglycemia risk in NPO patients 1, 8
• Consider more conservative dose reductions in this population 8

Monitoring and Adjustment Algorithm

1. Before NPO status: Identify patients at risk (kidney disease, previous hypoglycemia, variable oral intake) 8
2. At initiation of NPO: Reduce basal insulin to 60-80% of usual dose 1, 2
3. Every 4-6 hours: Check blood glucose and administer correction insulin as needed 1, 2
4. Daily reassessment: Adjust basal insulin based on glucose trends - if persistent hyperglycemia occurs, increase dose; if hypoglycemia occurs, reduce by an additional 20% 2, 8
5. When resuming oral intake: Transition to full basal-bolus regimen with prandial insulin coverage 1