For a 49‑year‑old woman with type 2 diabetes mellitus, BMI 41 kg/m², weight 123 kg, hemoglobin A1c 10.9 %, normal renal and hepatic function, and no severe hypoglycemia unawareness, what initial insulin glargine (Lantus) dose, carbohydrate‑to‑insulin ratio, and correction factor should be used?

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Last updated: February 14, 2026 • View editorial policy

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Insulin Dosing for a 49‑Year‑Old Woman with Severe Uncontrolled Type 2 Diabetes

For this patient with BMI 41 kg/m², weight 123 kg, and HbA1c 10.9 %, immediate basal‑bolus insulin therapy is required: start Lantus at 25–30 units once daily (0.2–0.25 units/kg/day) and add 4–6 units of rapid‑acting insulin before each of the three largest meals, while continuing metformin at maximum tolerated dose.12

Immediate Insulin Regimen

Basal Insulin (Lantus) Dosing

  • Start Lantus at 25–30 units once daily (approximately 0.2–0.25 units/kg/day for 123 kg), administered at bedtime or the same time each day.12
  • The standard starting range of 0.1–0.2 units/kg/day (12–25 units) is insufficient for HbA1c 10.9 %; patients with severe hyperglycemia (HbA1c ≥ 9 %) require higher initial doses of 0.3–0.5 units/kg/day total insulin, but given obesity and insulin resistance, starting conservatively at 0.2–0.25 units/kg/day for basal alone is appropriate.12

Prandial Insulin Coverage

  • Start 4–6 units of rapid‑acting insulin (lispro, aspart, or glulisine) before each of the three largest meals (breakfast, lunch, dinner), administered 0–15 minutes before eating.12
  • At HbA1c 10.9 %, basal insulin alone will be inadequate; prandial coverage is required from the outset to address both fasting and postprandial hyperglycemia.12

Titration Protocols

Basal Insulin (Lantus) Titration

  • Increase Lantus by 4 units every 3 days if fasting glucose is ≥ 180 mg/dL.1
  • Increase Lantus by 2 units every 3 days if fasting glucose is 140–179 mg/dL.1
  • Target fasting glucose: 80–130 mg/dL.1
  • Critical threshold: When Lantus approaches 0.5 units/kg/day (≈ 62 units), stop further basal escalation and intensify prandial insulin instead to avoid "over‑basalization" with increased hypoglycemia risk.1

Prandial Insulin Titration

  • Increase each meal dose by 1–2 units every 3 days based on the 2‑hour postprandial glucose reading for that meal.12
  • Target postprandial glucose: < 180 mg/dL.1
  • If unexplained hypoglycemia (glucose < 70 mg/dL) occurs, reduce the implicated dose by 10–20 % immediately.1

Carbohydrate‑to‑Insulin Ratio (Initial Estimate)

  • Start with a 1:10 ratio (1 unit per 10 grams of carbohydrate) as a reasonable initial estimate for patients with obesity and insulin resistance.1
  • The formula 450 ÷ total daily insulin dose can be used once the total daily dose is established; for example, if total daily insulin reaches 60 units, the ratio would be 450 ÷ 60 = 1 unit per 7.5 grams of carbohydrate.1
  • Adjust the ratio every 3 days if postprandial glucose consistently misses the target (< 180 mg/dL); tighten the ratio (e.g., 1:8 or 1:7) if postprandial glucose remains elevated.1

Correction Factor (Insulin Sensitivity Factor)

  • Initial correction scale (simplified approach):
    • Add 2 units of rapid‑acting insulin for pre‑meal glucose > 250 mg/dL.1
    • Add 4 units for pre‑meal glucose > 350 mg/dL.1
  • Individualized correction factor: Once total daily insulin dose is established, calculate the insulin sensitivity factor (ISF) as 1500 ÷ total daily dose (for regular insulin) or 1700 ÷ total daily dose (for rapid‑acting analogs).1
    • For example, if total daily insulin is 60 units, ISF = 1500 ÷ 60 = 25 mg/dL per unit (i.e., 1 unit lowers glucose by ≈ 25 mg/dL).1
    • Correction dose = (Current glucose – Target glucose) ÷ ISF.1
  • Adjust the ISF every 3 days if correction doses consistently fail to bring glucose into target range or cause hypoglycemia.1

Foundation Therapy: Metformin Must Continue

  • Continue or start metformin at maximum tolerated dose (up to 2000–2550 mg daily) unless contraindicated.12
  • Metformin reduces total insulin requirements by 20–30 % and provides superior glycemic control when combined with insulin compared with insulin alone.12
  • Do not discontinue metformin when starting insulin; this is a common pitfall that leads to higher insulin requirements and more weight gain.1

Monitoring Requirements

  • Check fasting glucose daily during the titration phase to guide Lantus adjustments.1
  • Check pre‑meal glucose before each meal to calculate correction doses.1
  • Obtain 2‑hour postprandial glucose after each meal to assess prandial insulin adequacy and guide titration.1
  • Reassess HbA1c every 3 months during intensive titration; expect an HbA1c reduction of 2–3 % (from 10.9 % to ≈ 8–9 %) over 3–6 months with appropriate basal‑bolus therapy.2

Expected Clinical Outcomes

  • With properly implemented basal‑bolus therapy at weight‑based dosing, ≈ 68 % of patients achieve mean glucose < 140 mg/dL, compared with ≈ 38 % on sliding‑scale insulin alone.1
  • HbA1c reduction of 2–3 % is achievable over 3–6 months with intensive titration.2
  • Correctly executed basal‑bolus regimens do not increase hypoglycemia incidence compared with inadequate sliding‑scale approaches.1

Hypoglycemia Management

  • Treat glucose < 70 mg/dL immediately with 15 grams of fast‑acting carbohydrate, recheck in 15 minutes, and repeat if needed.1
  • If hypoglycemia occurs without an obvious cause, reduce the implicated insulin dose by 10–20 % promptly.1
  • Never administer rapid‑acting insulin at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk.1

Critical Pitfalls to Avoid

  • Do not delay prandial insulin initiation when HbA1c is 10.9 %; basal insulin alone will be insufficient, and prolonged severe hyperglycemia increases complication risk.12
  • Do not continue escalating Lantus beyond 0.5–1.0 units/kg/day (62–123 units) without addressing postprandial hyperglycemia; this leads to over‑basalization with increased hypoglycemia risk and suboptimal control.1
  • Do not discontinue metformin when starting insulin unless contraindicated; this leads to higher insulin requirements and more weight gain.12
  • Do not rely solely on correction insulin without scheduled basal and prandial doses; sliding‑scale insulin as monotherapy is condemned by major diabetes guidelines as ineffective and unsafe.1

Patient Education Essentials

  • Insulin injection technique and site rotation to prevent lipohypertrophy.1
  • Hypoglycemia recognition and treatment (symptoms, < 70 mg/dL threshold, 15‑gram carbohydrate rule).1
  • Self‑monitoring of blood glucose: at least four daily measurements (fasting, pre‑meal, bedtime) during titration.1
  • "Sick day" management: continue insulin even if not eating, check glucose every 4 hours, maintain hydration.1
  • Ketone testing when glucose > 300 mg/dL with nausea/vomiting.1

References

1
Guideline

Initial Dosing for Lantus (Insulin Glargine) in Patients Requiring Insulin Therapy

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

2
Guideline

Insulin Dosing and Discharge Plan for Type 2 Diabetes with Severe Hyperglycemia

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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