What is the recommended basal‑bolus insulin regimen, including starting total daily dose, basal‑to‑bolus split, and glucose monitoring, for an adult with type 1 diabetes or a type 2 diabetic uncontrolled on oral agents who can perform multiple daily injections?

Basal-Bolus Insulin Regimen for Type 1 Diabetes and Uncontrolled Type 2 Diabetes

For adults with type 1 diabetes or type 2 diabetes uncontrolled on oral agents who can perform multiple daily injections, initiate a basal-bolus regimen with a total daily dose of 0.5 units/kg/day for type 1 diabetes (split 40–50% basal and 50–60% prandial) or 0.3–0.5 units/kg/day for type 2 diabetes (split 50% basal and 50% prandial), administered as once-daily long-acting insulin (glargine, detemir, or degludec) and rapid-acting insulin (lispro, aspart, or glulisine) 0–15 minutes before each of three meals. 1, 2

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Starting Total Daily Dose

Type 1 Diabetes

• Begin with 0.5 units/kg/day as the standard starting point for metabolically stable adults; the acceptable range is 0.4–1.0 units/kg/day. 1
• Patients in the honeymoon phase or with residual beta-cell function may require lower doses of 0.2–0.6 units/kg/day. 1
• Higher doses (approaching 1.0 units/kg/day) are needed during puberty, pregnancy, or acute illness. 1
• Patients presenting with diabetic ketoacidosis require higher initial doses of 0.6–1.0 units/kg/day before subsequent titration. 1

Type 2 Diabetes

• For insulin-naive patients with moderate hyperglycemia (HbA1c < 9%), start with 10 units once daily or 0.1–0.2 units/kg/day of basal insulin alone, continuing metformin and possibly one additional oral agent. 1
• For severe hyperglycemia (HbA1c ≥ 9%, blood glucose ≥ 300–350 mg/dL, or symptomatic/catabolic features), initiate a full basal-bolus regimen immediately with 0.3–0.5 units/kg/day total daily dose. 1, 2
• For high-risk patients (age > 65 years, renal impairment, poor oral intake), use lower starting doses of 0.1–0.25 units/kg/day to minimize hypoglycemia risk. 1, 2

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Basal-to-Bolus Split

Type 1 Diabetes

• Allocate 40–50% of the total daily dose as basal insulin (long-acting analog given once daily, typically at bedtime). 1
• Allocate 50–60% of the total daily dose as prandial insulin (rapid-acting analog divided among three meals). 1
• For a 70 kg patient: 0.5 units/kg/day = 35 units total → 14–18 units basal (once daily) + 17–21 units prandial (≈ 6–7 units per meal). 1

Type 2 Diabetes

• Use a 50:50 split between basal and prandial insulin for patients requiring full basal-bolus therapy. 1, 2
• For a 70 kg patient starting at 0.4 units/kg/day: 28 units total → 14 units basal (once daily) + 14 units prandial (≈ 4–5 units per meal). 1, 2
• When transitioning from basal-only therapy, add prandial insulin when basal insulin exceeds 0.5 units/kg/day without achieving HbA1c goals, or when fasting glucose is controlled but HbA1c remains above target after 3–6 months. 1

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Insulin Selection and Administration

Basal Insulin Options

• Insulin glargine (Lantus, Toujeo): Once-daily dosing, typically at bedtime or the same time each day. 1, 3
• Insulin detemir (Levemir): Once or twice-daily dosing; may require 38% higher total daily dose than glargine for equivalent control. 1
• Insulin degludec (Tresiba): Once-daily dosing at any time of day (adults) or the same time daily (pediatrics); allows ≥ 8 hours between doses if missed. 3

Prandial Insulin Options

• Rapid-acting analogs (lispro, aspart, glulisine): Administer 0–15 minutes before meals for optimal postprandial control; onset 0.25–0.5 hours, peak 1–3 hours, duration 3–5 hours. 1, 2
• Regular human insulin: Administer 30–45 minutes before meals; slower onset and longer duration than rapid-acting analogs. 1
• Ultra-rapid-acting analogs (faster aspart, ultra-rapid lispro): May be considered for patients requiring more immediate postprandial coverage. 2

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Glucose Monitoring

Frequency

• Type 1 diabetes: Check glucose before each meal, at bedtime, occasionally 2 hours postprandial, before exercise, and when hypoglycemia is suspected—typically 6–10 checks per day during intensive management. 1
• Type 2 diabetes on basal-bolus therapy: Check glucose fasting daily, before each meal, and 2 hours postprandial during titration; minimum 4 checks daily. 1, 2
• Hospitalized patients eating regular meals: Check glucose before each meal and at bedtime. 1
• Hospitalized patients NPO or with poor intake: Check glucose every 4–6 hours. 1

Targets

• Fasting/pre-meal glucose: 80–130 mg/dL (4.4–7.2 mmol/L). 1
• Postprandial glucose (2 hours after meals): < 180 mg/dL (< 10.0 mmol/L). 1, 4
• HbA1c: < 7.0% for most adults; < 7.5% (< 58 mmol/mol) for children with type 1 diabetes. 5
• Hospitalized non-critically ill patients: 140–180 mg/dL; more stringent targets of 110–140 mg/dL may be appropriate for selected stable patients. 1

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Titration Protocols

Basal Insulin Titration

• Fasting glucose 140–179 mg/dL: Increase basal dose by 2 units every 3 days. 1, 2
• Fasting glucose ≥ 180 mg/dL: Increase basal dose by 4 units every 3 days. 1, 2
• Target fasting glucose: 80–130 mg/dL. 1
• If hypoglycemia occurs (glucose < 70 mg/dL) without clear cause: Reduce basal dose by 10–20% immediately. 1, 2

Prandial Insulin Titration

• Adjust each meal dose by 1–2 units (or 10–15%) every 3 days based on the 2-hour postprandial glucose reading for that meal. 1, 2
• Target postprandial glucose: < 180 mg/dL. 1
• If hypoglycemia occurs after a specific meal, reduce that meal's prandial dose by 10–20%. 1

Carbohydrate-Based Dosing (Advanced)

• Calculate an insulin-to-carbohydrate ratio (ICR) using the formula: 450 ÷ total daily dose (for rapid-acting analogs) or 500 ÷ total daily dose (for regular insulin). 1
• Example: Total daily dose of 45 units → ICR = 450 ÷ 45 = 1 unit per 10 grams of carbohydrate. 1
• A common starting ratio is 1 unit per 10–15 grams of carbohydrate. 1

Correction (Supplemental) Insulin

• Add 2 units of rapid-acting insulin for pre-meal glucose > 250 mg/dL. 1
• Add 4 units of rapid-acting insulin for pre-meal glucose > 350 mg/dL. 1
• For individualized correction, calculate an insulin sensitivity factor (ISF): 1500 ÷ total daily dose (for regular insulin) or 1700 ÷ total daily dose (for rapid-acting analogs). 1
• Correction dose = (Current glucose – Target glucose) ÷ ISF. 1

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Critical Threshold: Recognizing "Over-Basalization"

• When basal insulin approaches 0.5–1.0 units/kg/day without achieving glycemic targets, add or intensify prandial insulin rather than continuing to escalate basal insulin alone. 1, 2
• Clinical signals of over-basalization include: basal dose > 0.5 units/kg/day, bedtime-to-morning glucose differential ≥ 50 mg/dL, hypoglycemia episodes, and high glucose variability. 1
• Further basal escalation beyond this threshold produces diminishing returns with increased hypoglycemia risk. 1

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Stepwise Intensification for Type 2 Diabetes

Step 1: Basal Insulin Only

• Start with 10 units once daily or 0.1–0.2 units/kg/day of long-acting insulin, continuing metformin (unless contraindicated) and possibly one additional oral agent. 1
• Titrate by 2–4 units every 3 days until fasting glucose reaches 80–130 mg/dL. 1

Step 2: Basal-Plus (Single Prandial Dose)

• When basal insulin is optimized but HbA1c remains above goal after 3–6 months, add 4 units of rapid-acting insulin before the largest meal (or 10% of the basal dose). 1, 2, 4, 6
• Titrate this single prandial dose by 1–2 units every 3 days based on 2-hour postprandial glucose. 1, 2

Step 3: Basal-Plus-Plus (Two Prandial Doses)

• If HbA1c remains above goal, add a second prandial dose before the next largest meal, starting with 4 units. 2, 6
• Continue titration based on postprandial glucose readings. 2

Step 4: Full Basal-Bolus (Three Prandial Doses)

• Add a third prandial dose before the remaining meal to achieve a full basal-bolus regimen with three pre-meal injections. 2, 4, 6
• This stepwise approach allows gradual intensification while minimizing injection burden. 2, 6

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Foundation Therapy: Continue Metformin

• Continue metformin at maximum tolerated dose (up to 2,000–2,550 mg/day) when initiating or intensifying insulin therapy, unless contraindicated. 1, 5
• Metformin reduces total insulin requirements by 20–30%, provides superior glycemic control, and limits weight gain compared with insulin alone. 1
• Discontinue sulfonylureas when advancing beyond basal-only insulin to prevent additive hypoglycemia risk. 1

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Hypoglycemia Management

• Treat any glucose < 70 mg/dL immediately with 15 grams of fast-acting carbohydrate (e.g., glucose tablets, juice), recheck in 15 minutes, and repeat if needed. 1
• If hypoglycemia occurs without an obvious cause, reduce the implicated insulin dose by 10–20% immediately before the next administration. 1, 2
• Never administer rapid-acting insulin at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk. 1
• Scrupulous avoidance of hypoglycemia for 2–3 weeks can reverse hypoglycemia unawareness if present. 1

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Common Pitfalls to Avoid

• Never use sliding-scale insulin as monotherapy in type 1 diabetes or as the sole regimen in type 2 diabetes; it is condemned by all major diabetes guidelines as ineffective and unsafe. 1, 7
• Do not delay insulin initiation in patients not achieving glycemic goals with oral medications; this prolongs hyperglycemia exposure and increases complication risk. 1
• Do not discontinue metformin when starting insulin unless contraindicated; this leads to higher insulin requirements and more weight gain. 1, 5
• Do not continue escalating basal insulin beyond 0.5–1.0 units/kg/day without addressing postprandial hyperglycemia; this causes over-basalization with increased hypoglycemia risk and suboptimal control. 1, 2
• Do not abruptly discontinue oral medications when starting insulin; continue metformin and discontinue sulfonylureas only when advancing beyond basal-only therapy. 1, 5

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Patient Education Essentials

• Insulin injection technique and site rotation to prevent lipohypertrophy; use the shortest needles (4-mm pen or 6-mm syringe) as first-line choice. 1, 5
• Recognition and treatment of hypoglycemia: symptoms, < 70 mg/dL threshold, 15-gram carbohydrate rule. 1
• Self-monitoring of blood glucose: at least 4 checks daily during titration (fasting, pre-meal, bedtime, occasional postprandial). 1
• "Sick day" management rules: continue insulin even if not eating, check glucose every 4 hours, maintain hydration, check ketones if glucose > 300 mg/dL with symptoms. 1
• Insulin storage and handling: store unopened vials/pens in refrigerator; in-use vials/pens may be kept at room temperature for up to 28–42 days depending on formulation. 1

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Expected Clinical Outcomes

• With appropriately implemented basal-bolus therapy, ≈ 68% of patients achieve mean glucose < 140 mg/dL versus ≈ 38% with sliding-scale insulin alone. 1, 7
• HbA1c reduction of 2–3% (or 3–4% in severe hyperglycemia) is achievable over 3–6 months with intensive titration. 1
• Properly executed basal-bolus regimens do not increase overall hypoglycemia incidence compared with inadequate sliding-scale approaches. 1, 7
• Basal-bolus therapy is associated with fewer hypoglycemic events and less weight gain compared with premixed insulin regimens. 7