Insulin Dosing for a 49‑Year‑Old Female with Severe Uncontrolled Type 2 Diabetes
For this patient (weight 123 kg, BMI 41, A1c 10.9 %), start insulin glargine (Lantus) at 25 units once daily at bedtime, use a carbohydrate‑to‑insulin ratio of 1:10 (1 unit per 10 g carbohydrate) for prandial insulin, and apply an insulin sensitivity factor of 30 mg/dL per unit for correction doses.
Initial Basal Insulin (Lantus) Dose
Start with 0.2 units/kg/day (≈ 25 units once daily at bedtime) given the severe hyperglycemia (A1c 10.9 %). The standard starting range for insulin‑naïve type 2 diabetes patients is 10 units or 0.1–0.2 units/kg/day, but patients with A1c ≥ 9 % warrant the higher end of this range to achieve glycemic targets faster 1.
Administer Lantus at the same time each evening (ideally 20:00 h) to maintain stable 24‑hour basal coverage 1.
Continue metformin at the maximum tolerated dose (up to 2,000–2,550 mg/day) unless contraindicated; this combination reduces total insulin requirements by 20–30 % and provides superior glycemic control compared with insulin alone 1.
Basal Insulin Titration Protocol
Increase Lantus by 2 units every 3 days if fasting glucose is 140–179 mg/dL 1.
Increase Lantus by 4 units every 3 days if fasting glucose is ≥ 180 mg/dL 1.
Target fasting glucose: 80–130 mg/dL 1.
Stop escalating basal insulin when the dose approaches 0.5 units/kg/day (≈ 62 units for this patient). Beyond this threshold, add prandial insulin rather than continuing basal escalation to avoid "over‑basalization," which increases hypoglycemia risk without improving control 1.
If unexplained hypoglycemia (glucose < 70 mg/dL) occurs, reduce the current basal dose by 10–20 % immediately 1.
Carbohydrate‑to‑Insulin Ratio (Prandial Insulin)
Start with a 1:10 ratio (1 unit of rapid‑acting insulin per 10 g carbohydrate) for meal coverage 1.
This ratio can be calculated using the formula 450 ÷ total daily insulin dose (TDD). For example, if the patient's TDD reaches 50 units after titration, the ratio becomes 450 ÷ 50 = 9 g carbohydrate per unit (≈ 1:9) 1.
Initiate prandial insulin when:
Start with 4 units of rapid‑acting insulin (lispro, aspart, or glulisine) before the largest meal, or use 10 % of the current basal dose 1.
Administer rapid‑acting insulin 0–15 minutes before meals for optimal postprandial control 1.
Titrate each meal dose by 1–2 units (≈ 10–15 %) every 3 days based on 2‑hour postprandial glucose readings, targeting postprandial glucose < 180 mg/dL 1.
Insulin Sensitivity Factor (Correction Scale)
Use an insulin sensitivity factor (ISF) of 1,500 ÷ TDD for regular insulin or 1,700 ÷ TDD for rapid‑acting analogs 1.
For a patient with an estimated TDD of 50 units, the ISF is 1,500 ÷ 50 = 30 mg/dL per unit (i.e., 1 unit of insulin lowers glucose by ≈ 30 mg/dL) 1.
Simplified correction protocol (for patients not using carbohydrate counting):
Correction doses are always given in addition to scheduled prandial insulin, never as a replacement 1.
Never administer rapid‑acting insulin at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk 1.
Monitoring Requirements
Check fasting glucose daily during the titration phase to guide basal insulin adjustments 1.
Measure pre‑meal glucose before each meal to calculate correction doses 1.
Obtain 2‑hour postprandial glucose after meals to assess prandial insulin adequacy and guide further titration 1.
Reassess A1c every 3 months during intensive titration 1.
Expected Clinical Outcomes
With properly implemented basal‑bolus therapy, ≈ 68 % of patients achieve mean glucose < 140 mg/dL, compared with ≈ 38 % on sliding‑scale insulin alone 1.
A1c reduction of 2–3 % (from 10.9 % to ≈ 7.9–8.9 %) is achievable within 3–6 months with intensive titration 1.
Correctly executed basal‑bolus regimens do not increase hypoglycemia incidence compared with inadequate sliding‑scale approaches 1.
Critical Thresholds and Warning Signs
Signs of "over‑basalization" that require adding prandial insulin rather than further basal escalation 1:
- Basal dose > 0.5 units/kg/day (≈ 62 units for this patient).
- Bedtime‑to‑morning glucose differential ≥ 50 mg/dL.
- Recurrent hypoglycemia episodes.
- High glucose variability throughout the day.
When basal insulin approaches 0.5–1.0 units/kg/day without achieving glycemic targets, add prandial insulin or a GLP‑1 receptor agonist rather than continuing basal escalation 1.
Hypoglycemia Management
Treat any glucose < 70 mg/dL immediately with 15 g 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.
Common Pitfalls to Avoid
Do not delay insulin initiation in patients not achieving glycemic goals with oral medications; prolonged hyperglycemia increases complication risk 1.
Do not discontinue metformin when starting insulin unless contraindicated; this leads to higher insulin requirements and more weight gain 1.
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.
Do not rely solely on correction insulin without adjusting scheduled basal and prandial doses; this perpetuates inadequate control 1.