What is an appropriate sliding‑scale dosing protocol for regular (short‑acting) insulin in adult inpatients?

Sliding‑Scale Insulin Is Not Recommended as a Primary Regimen

Sliding‑scale insulin (SSI) used alone is strongly discouraged by all major diabetes guidelines and should be replaced immediately with a scheduled basal‑bolus insulin regimen for hospitalized adults with diabetes. 1, 2, 3

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Why Sliding‑Scale Insulin Fails

• SSI treats hyperglycemia reactively after glucose spikes, rather than preventing it, leading to dangerous glucose fluctuations that worsen both hyper‑ and hypoglycemia. 1, 2, 4, 5
• Only ≈38 % of patients on SSI alone achieve mean glucose < 140 mg/dL, compared with ≈68 % using a scheduled basal‑bolus approach. 1, 2, 6
• SSI regimens are often left unchanged throughout hospitalization even when control remains poor, perpetuating inadequate management. 2, 7
• Meta‑analysis of 11 RCTs (1,322 patients) showed SSI resulted in significantly higher mean glucose and increased hyperglycemic events without any benefit in glycemic control. 8
• In one observational study, SSI was subtherapeutic after 84 % of injections, with glucose remaining elevated despite treatment. 7

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The Correct Approach: Scheduled Basal‑Bolus Insulin

Initial Dosing

• Standard‑risk patients (insulin‑naïve or low‑dose home therapy): start with 0.3–0.5 U/kg/day total daily dose, split 50 % basal (once daily) and 50 % prandial (divided among three meals). 1, 2, 3
• High‑risk patients (age > 65 yr, renal impairment, poor oral intake): use 0.1–0.25 U/kg/day to minimize hypoglycemia risk. 1, 2, 3
• Patients on high‑dose home insulin (≥0.6 U/kg/day): reduce total daily dose by 20 % on admission. 1, 2, 3

Basal Insulin Titration

• Increase basal dose by 2 U every 3 days if fasting glucose is 140–179 mg/dL. 1
• Increase basal dose by 4 U every 3 days if fasting glucose is ≥180 mg/dL. 1
• Target fasting glucose 80–130 mg/dL. 1
• Stop basal escalation when dose reaches 0.5–1.0 U/kg/day without achieving targets; add prandial insulin instead. 1

Prandial Insulin

• Start with 4 U rapid‑acting insulin before each of the three largest meals (or ≈10 % of current basal dose). 1
• Administer 0–15 minutes before meals. 1
• Titrate each meal dose by 1–2 U (≈10–15 %) every 3 days based on 2‑hour post‑prandial glucose. 1
• Target post‑prandial glucose < 180 mg/dL. 1

Correction Doses (Adjunct Only)

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

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When SSI Might Be Acceptable (Rare Exceptions)

• Mild stress hyperglycemia in patients without pre‑existing diabetes. 2, 3
• Well‑controlled diabetes (HbA1c < 7 %) on minimal home therapy with only mild hyperglycemia during hospitalization. 2, 3
• NPO patients with no nutritional replacement and only mild hyperglycemia. 2, 3
• New steroid therapy or patients tapering steroids. 2, 3

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Clinical Outcomes: Basal‑Bolus vs SSI

• Glycemic control: 68 % of patients on basal‑bolus achieve mean glucose < 140 mg/dL versus 38 % on SSI alone. 1, 2, 6
• Complications: Basal‑bolus therapy reduces postoperative wound infections and acute renal failure compared with SSI. 2
• Hypoglycemia: Properly implemented basal‑bolus regimens do not increase hypoglycemia incidence compared with SSI. 1, 6
• Target glucose range for non‑critically ill hospitalized patients: 140–180 mg/dL. 1, 2

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Monitoring Requirements

• Patients eating regular meals: check glucose before each meal and at bedtime (minimum 4 times daily). 1
• Patients with poor intake or NPO: check glucose every 4–6 hours. 1
• Use daily fasting glucose to guide basal insulin adjustments. 1
• Obtain 2‑hour post‑prandial glucose after each meal to assess prandial adequacy. 1

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Critical Pitfalls to Avoid

• Never use SSI as monotherapy in hospitalized patients with diabetes—it is condemned by all major guidelines. 1, 2, 3, 4, 8, 5
• Never use SSI as monotherapy in type 1 diabetes—it can precipitate diabetic ketoacidosis. 1, 3
• Do not delay adding prandial insulin when basal insulin alone fails to achieve target fasting glucose. 1
• Do not rely solely on correction doses without adjusting scheduled basal and prandial insulin. 1, 2, 3
• Avoid premixed insulin (70/30) in hospitals due to unacceptably high hypoglycemia rates (64 % vs 24 % with basal‑bolus). 1, 2, 3, 6
• Do not give rapid‑acting insulin at bedtime as a sole correction dose—it markedly raises nocturnal hypoglycemia risk. 1

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Hypoglycemia Management

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

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Summary Algorithm

1. Discontinue SSI as monotherapy immediately. 1, 2, 3
2. Start basal insulin (glargine, detemir, or degludec) at 0.3–0.5 U/kg/day (50 % of total dose). 1, 2, 3
3. Start prandial insulin (lispro, aspart, or glulisine) at 4 U before each meal (50 % of total dose divided). 1, 2, 3
4. Add correction doses (2 U for glucose > 250 mg/dL; 4 U for > 350 mg/dL) as a supplement only. 1, 2
5. Titrate basal insulin every 3 days based on fasting glucose. 1
6. Titrate prandial insulin every 3 days based on 2‑hour post‑prandial glucose. 1
7. Monitor glucose before each meal and at bedtime. 1