For a 70‑kg adult patient, how many units of insulin aspart should be prescribed to cover three months of sliding‑scale supplementation?

Prescribing Insulin Aspart for 3‑Month Sliding‑Scale Supplementation: Evidence‑Based Guidance

Sliding‑Scale Insulin as Monotherapy Is Explicitly Condemned and Should Not Be Prescribed

Major diabetes guideline societies—including the American Diabetes Association, the Endocrine Society, and the American College of Physicians—explicitly condemn the use of sliding‑scale insulin (SSI) as the sole insulin regimen for any patient requiring insulin therapy. 1, 2, 3 This reactive approach treats hyperglycemia only after it occurs, leading to dangerous glucose fluctuations that worsen both hyper‑ and hypoglycemia. 1, 2, 3

Why Sliding‑Scale Monotherapy Fails

• Only ≈38 % of patients achieve a mean glucose < 140 mg/dL with SSI alone, compared with ≈68 % when a scheduled basal‑bolus regimen is used. 1, 2, 3
• SSI provides no basal insulin to suppress hepatic glucose production between meals and overnight, resulting in persistent fasting hyperglycemia. 1, 2, 3
• SSI lacks scheduled prandial insulin, causing post‑prandial spikes that are later corrected with large reactive doses, creating a cycle of hyperglycemia → large correction → hypoglycemia → rebound hyperglycemia. 1, 2, 3
• In hospitalized patients, SSI monotherapy is associated with a 3‑fold higher risk of hyperglycemic episodes compared with no pharmacologic regimen at all. 4
• Retrospective studies show that SSI is ineffectual in 84 % of administered doses, with glucose levels remaining elevated despite repeated injections. 5

The Correct Prescription: Basal‑Bolus Insulin Regimen with Correction Doses

For a 70‑kg adult requiring insulin therapy, prescribe a scheduled basal‑bolus regimen comprising basal insulin (long‑acting), prandial insulin (rapid‑acting before meals), and correction doses of insulin aspart as a supplement—never as monotherapy. 1, 2, 3

Initial Dosing Algorithm

Component	Starting Dose	Timing	Purpose
Basal insulin (glargine, detemir, or degludec)	10 units once daily (or 0.1–0.2 U/kg = 7–14 U for 70 kg)	Bedtime or same time daily	Suppresses hepatic glucose production 24 hours; prevents fasting hyperglycemia [1,2,3]
Prandial insulin aspart	4 units before each of the three largest meals (total ≈12 U/day)	0–15 minutes before meals	Covers meal‑related glucose excursions [1,2,3]
Correction insulin aspart	2 U for pre‑meal glucose > 250 mg/dL; 4 U for > 350 mg/dL	In addition to scheduled prandial dose	Supplements scheduled insulin when glucose exceeds target [1,2,3]

Three‑Month Supply Calculation

• Basal insulin: 10 U/day × 90 days = 900 units (≈9 vials of 10 mL at 100 U/mL, or ≈3 boxes of prefilled pens).
• Prandial insulin aspart: 12 U/day × 90 days = 1,080 units (≈11 vials or ≈4 boxes of pens).
• Correction insulin aspart: Estimate ≈2–4 U/day average × 90 days = 180–360 units (≈2–4 vials or ≈1 box of pens).
• Total insulin aspart for 3 months: ≈1,260–1,440 units (≈13–15 vials or ≈5 boxes of prefilled pens).

Prescribe insulin aspart in a quantity sufficient to cover both scheduled prandial doses and anticipated correction doses for 90 days, typically ≈1,500 units (15 vials or 5 boxes of pens). 1, 2, 3

Titration Protocols for Optimal Glycemic Control

Basal Insulin Titration

• Increase basal dose by 2 U every 3 days if fasting glucose is 140–179 mg/dL. 1, 2, 3
• Increase basal dose by 4 U every 3 days if fasting glucose is ≥180 mg/dL. 1, 2, 3
• Target fasting glucose 80–130 mg/dL. 1, 2, 3
• Stop basal escalation when the dose approaches 0.5 U/kg/day (≈35 U for 70 kg) without achieving targets; add or intensify prandial insulin instead. 1, 2, 3

Prandial Insulin Aspart Titration

• Increase each meal dose by 1–2 U (≈10–15 %) every 3 days based on the 2‑hour post‑prandial glucose reading. 1, 2, 3
• Target post‑prandial glucose < 180 mg/dL. 1, 2, 3
• Administer insulin aspart 0–15 minutes before meals (ideally immediately before eating) for optimal post‑prandial control. 1, 6

Correction Dose Protocol (Adjunct Only)

• Add 2 U of insulin aspart for pre‑meal glucose > 250 mg/dL. 1, 2, 3
• Add 4 U for pre‑meal glucose > 350 mg/dL. 1, 2, 3
• Correction doses must supplement—not replace—scheduled basal and prandial insulin. 1, 2, 3

Monitoring Requirements

• Daily fasting glucose to guide basal insulin adjustments. 1, 2, 3
• Pre‑meal glucose before each meal to calculate correction doses. 1, 2, 3
• 2‑hour post‑prandial glucose after each meal to assess prandial adequacy. 1, 2, 3
• HbA1c every 3 months until stable control is achieved. 1, 2, 3

Expected Clinical Outcomes

• With properly implemented basal‑bolus therapy using insulin aspart, ≈68 % of patients achieve mean glucose < 140 mg/dL versus ≈38 % with SSI alone. 1, 2, 3
• Insulin aspart shows a lower incidence of major or nocturnal hypoglycemic events compared with regular human insulin, while providing similar overall tolerability. 1, 6
• The faster onset and shorter duration of insulin aspart allow more flexible meal timing and better post‑prandial glucose control than regular insulin. 1, 6

Critical Pitfalls to Avoid

• Never prescribe insulin aspart as sliding‑scale monotherapy; this approach is condemned by all major diabetes guidelines and shown to be ineffective. 1, 2, 3, 4, 5
• Do not delay adding prandial insulin when basal insulin alone fails to achieve targets. 1, 2, 3
• Never use insulin aspart at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk. 1, 2, 3
• Do not rely solely on correction doses without adjusting scheduled basal and prandial insulin when frequent corrections are needed. 1, 2, 3

Hypoglycemia Management

• Treat glucose < 70 mg/dL promptly with 15 g of fast‑acting carbohydrate, recheck in 15 minutes, and repeat if needed. 1, 2, 3
• If hypoglycemia occurs without an obvious cause, reduce the implicated insulin dose by 10–20 % immediately. 1, 2, 3

Sample Prescription

Insulin aspart (NovoLog®, Humalog®, or Apidra®)

• Quantity: 1,500 units (15 vials of 10 mL at 100 U/mL, or 5 boxes of prefilled pens)
• Directions: Administer 4 units subcutaneously 0–15 minutes before each of the three largest meals. Add 2 units for pre‑meal glucose > 250 mg/dL or 4 units for > 350 mg/dL. Titrate each meal dose by 1–2 units every 3 days based on 2‑hour post‑prandial glucose, targeting < 180 mg/dL.
• Refills: 0 (reassess after 3 months)

Insulin glargine (Lantus®, Basaglar®, or Toujeo®)

• Quantity: 900 units (9 vials or 3 boxes of pens)
• Directions: Administer 10 units subcutaneously once daily at bedtime. Increase by 2 units every 3 days if fasting glucose 140–179 mg/dL, or by 4 units every 3 days if fasting glucose ≥180 mg/dL, targeting 80–130 mg/dL.
• Refills: 0 (reassess after 3 months)