How do I adjust the dose of long‑acting basal insulin (e.g., insulin glargine, insulin degludec) based on fasting glucose targets, hypoglycemia, and patient factors such as age, renal or hepatic impairment, and what interval should I wait between dose changes?

Long-Acting Basal Insulin Dose Adjustment

Adjust long-acting basal insulin by increasing 2 units every 3 days when fasting glucose is 140–179 mg/dL, or by 4 units every 3 days when fasting glucose is ≥180 mg/dL, targeting 80–130 mg/dL; if hypoglycemia occurs, reduce the dose by 10–20% immediately.1

Standard Titration Algorithm

• Start with 10 units once daily or 0.1–0.2 units/kg/day for insulin-naïve patients with type 2 diabetes, administered at the same time each day.12
• Increase by 2 units every 3 days if fasting glucose is 140–179 mg/dL.12
• Increase by 4 units every 3 days if fasting glucose is ≥180 mg/dL.12
• Target fasting glucose: 80–130 mg/dL (4.4–7.2 mmol/L).12
• Wait 3 days between dose changes to allow steady-state pharmacokinetics and avoid day-to-day variability.2

Hypoglycemia-Driven Dose Reduction

• Reduce the dose by 10–20% immediately if any unexplained hypoglycemic episode (glucose <70 mg/dL) occurs—do not wait for the next scheduled adjustment.12
• If more than two fasting glucose values per week are <80 mg/dL, decrease the basal dose by 2 units.2
• Treat glucose <70 mg/dL with 15 g of fast-acting carbohydrate, recheck in 15 minutes, and repeat if needed.12

Patient-Specific Factors Requiring Lower Starting Doses

Age

• Elderly patients (>65 years): Start with 0.1–0.25 units/kg/day to minimize hypoglycemia risk; greater caution is required as older individuals may have increased sensitivity to insulin and difficulty recognizing hypoglycemia.123
• Pediatric patients (≥1 year): Start at a reduced dose compared to previous insulin therapy to minimize hypoglycemia risk; safety and effectiveness are not established in children <1 year.3

Renal Impairment

• eGFR <60 mL/min/1.73 m²: Start with 0.1–0.25 units/kg/day and intensify glucose monitoring; insulin clearance decreases with declining kidney function.123
• CKD Stage 5 (dialysis): Reduce total daily insulin by 50% for type 2 diabetes and 35–40% for type 1 diabetes.2
• No dose adjustment is required based solely on renal function, but individual titration with intensified monitoring is essential.3

Hepatic Impairment

• Mild, moderate, or severe hepatic impairment: No pharmacokinetic differences exist, but intensify glucose monitoring and adjust doses individually as insulin requirements may change unpredictably.23

Poor Oral Intake or NPO Status

• Hospitalized patients with limited intake: Start with 0.1–0.25 units/kg/day given primarily as basal insulin, with correction doses only for glucose >180 mg/dL.12
• Never completely withhold basal insulin in NPO patients, as it suppresses hepatic glucose production independent of food intake and prevents ketoacidosis.2

High-Dose Home Insulin Users

• Patients on ≥0.6 units/kg/day at home: Reduce total daily dose by 20% upon hospitalization to prevent hypoglycemia.12

Critical Threshold: When to Stop Escalating Basal Insulin

• 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.1245
• Clinical signals of "over-basalization" requiring cessation of basal escalation include:125
  • Basal dose >0.5 units/kg/day
  • Bedtime-to-morning glucose differential ≥50 mg/dL
  • Episodes of hypoglycemia despite overall hyperglycemia
  • High glucose variability throughout the day

Monitoring Requirements

• Daily fasting glucose checks are essential during titration to guide basal insulin adjustments.125
• Reassess every 3 days during active titration to adjust the dose.125
• Reassess every 3–6 months once stable to avoid therapeutic inertia.2
• Check HbA1c every 3 months during intensive titration.2

Special Considerations by Insulin Type

Insulin Glargine (Lantus, Basaglar, Semglee)

• Duration of action: up to 24 hours with a peakless profile; administer once daily at the same time.1467
• May require twice-daily dosing in type 1 diabetes when once-daily administration fails to provide 24-hour coverage, particularly with high glycemic variability.24
• Do not dilute or mix with any other insulin due to its acidic pH (~4).24

Insulin Glargine U-300 (Toujeo)

• Longer duration of action than U-100 glargine, providing more stable 24-hour coverage with reduced glucose variability.45
• Requires approximately 10–18% higher daily doses compared to U-100 glargine to achieve equivalent glycemic control.45
• Significantly lower rates of clinically significant hypoglycemia (<54 mg/dL) compared to U-100 glargine in head-to-head trials.45
• When switching from U-100 to U-300 glargine, increase the daily dose by 10–18% (e.g., 66 U Lantus → 73–78 U Toujeo).45

Insulin Degludec (Tresiba)

• Ultra-long duration of action (>42 hours) with the most consistent day-to-day pharmacodynamics; can be administered at any time of day.378
• Lower day-to-day variability in fasting glucose compared to glargine, particularly beneficial in type 1 diabetes.98
• Superior hypoglycemia safety profile: 40% lower rate of severe hypoglycemia compared to glargine in cardiovascular outcomes trial (4.9% vs. 6.6%).8
• Wait at least 1 week before making subsequent dose adjustments to fully assess glucose outcomes due to ultra-long half-life.2

Insulin Detemir (Levemir)

• Duration of action: up to 24 hours, but frequently requires twice-daily dosing to maintain 24-hour coverage.710
• When converting from glargine to detemir, the total daily dose of detemir should be approximately 38% higher than glargine.2

Perioperative and Acute Illness Management

• Reduce basal insulin by approximately 25% the evening before surgery to achieve target glucose with decreased hypoglycemia risk.2
• While NPO perioperatively, monitor glucose every 2–4 hours and treat with short- or rapid-acting insulin as needed; aim for 80–180 mg/dL.2
• During acute illness with poor oral intake, reduce to 0.1–0.25 units/kg/day for high-risk patients.12
• Glucocorticoid therapy can require extraordinary insulin amounts; increase prandial and correction insulin by 40–60% in addition to basal insulin.2

Foundation Therapy Maintenance

• Continue metformin (unless contraindicated) at maximum tolerated dose (up to 2,000–2,550 mg daily) throughout basal insulin titration; the combination reduces total insulin requirements by 20–30% and provides superior glycemic control.125
• Discontinue sulfonylureas when advancing beyond basal-only insulin to prevent hypoglycemia.2

Common Pitfalls to Avoid

• Never delay insulin initiation in patients not achieving glycemic goals with oral medications; prolonged hyperglycemia increases complication risk.12
• Never discontinue metformin when starting insulin unless contraindicated; this leads to higher insulin requirements and more weight gain.2
• Never 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.125
• Never reduce the dose based on a single low reading—look for patterns over 2–3 days before making adjustments.5
• Never completely withhold basal insulin in type 1 diabetes or insulin-dependent type 2 diabetes, even when NPO, to prevent diabetic ketoacidosis.2
• Do not wait longer than 3 days between basal insulin adjustments in stable patients; this unnecessarily prolongs time to achieve glycemic targets.2
• 75% of hospitalized patients who experience hypoglycemia receive no basal insulin dose adjustment before the next administration—this common management gap must be avoided.2