How should I initiate insulin glargine (Lantus) therapy, including starting dose, titration, administration, monitoring, and follow‑up?

Starting Lantus (Insulin Glargine) Therapy

Initial Dosing

For insulin-naïve adults with type 2 diabetes, start Lantus at 10 units once daily or 0.1–0.2 units/kg body weight, administered at the same time each day, while continuing metformin unless contraindicated. 1

• The standard starting dose is 10 units once daily for most patients with mild-to-moderate hyperglycemia 1
• Weight-based dosing of 0.1–0.2 units/kg/day is appropriate when fasting glucose is 200–300 mg/dL or HbA1c is 8–9% 1
• For severe hyperglycemia (HbA1c ≥9%, glucose ≥300 mg/dL, or symptomatic/catabolic features), consider higher starting doses of 0.3–0.5 units/kg/day as part of a basal-bolus regimen 1

Type 1 Diabetes Initiation

• For adults with type 1 diabetes, the total daily insulin requirement is typically 0.4–1.0 units/kg/day, with 0.5 units/kg/day being standard for metabolically stable patients 1
• Allocate approximately 40–50% of the total daily dose to Lantus as basal insulin, with the remaining 50–60% as rapid-acting prandial insulin 1
• Type 1 diabetes always requires a basal-bolus regimen from the outset; basal insulin alone is insufficient 1

Administration Technique

• Inject Lantus subcutaneously in the abdomen, thigh, or deltoid region 1
• Administer at the same time each day—typically bedtime (20:00 h), though morning dosing is acceptable if preferred 1, 2
• Never mix or dilute Lantus with any other insulin or solution due to its acidic pH (4.0); it must be given as a separate injection 3, 4
• Rotate injection sites within the same region to prevent lipohypertrophy 1

Systematic Titration Protocol

Increase Lantus by 2–4 units every 3 days based on fasting glucose values until the target range of 80–130 mg/dL is achieved. 1

Fasting Glucose	Dose Adjustment	Frequency
140–179 mg/dL	Increase by 2 units	Every 3 days
≥180 mg/dL	Increase by 4 units	Every 3 days
<80 mg/dL (≥2 readings/week)	Decrease by 2 units	Immediately
<70 mg/dL (any reading)	Decrease by 10–20%	Immediately

• Target fasting glucose: 80–130 mg/dL 3, 1
• Equip patients with a self-titration algorithm based on daily fasting glucose monitoring to improve glycemic control 3, 1

Monitoring Requirements

• Daily fasting glucose checks are essential during the titration phase 1
• Measure HbA1c every 3 months during intensive titration 1
• Reassess the insulin regimen every 3–6 months once stable to avoid therapeutic inertia 1
• Check for clinical signals of over-basalization at every visit: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia episodes, or high glucose variability 1

Critical Threshold: When to Stop Escalating Basal Insulin

When Lantus 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

• Further basal increases beyond this threshold lead to "over-basalization" with increased hypoglycemia risk and suboptimal control 1
• Signs requiring prandial insulin addition include:
  • Basal dose >0.5 units/kg/day with unmet HbA1c goal 1
  • Fasting glucose controlled (80–130 mg/dL) but HbA1c remains above target after 3–6 months 1
  • Significant postprandial glucose excursions (>180 mg/dL) 1

Adding Prandial Insulin

• Start with 4 units of rapid-acting insulin (lispro, aspart, or glulisine) before the largest meal 1
• Alternatively, use 10% of the current basal dose as the initial prandial amount 1
• Administer rapid-acting insulin 0–15 minutes before meals 1
• Titrate each meal dose by 1–2 units every 3 days based on 2-hour postprandial glucose, targeting <180 mg/dL 1

Combination Therapy with Metformin

Continue metformin at the maximum tolerated dose (up to 2,000–2,550 mg daily) when initiating Lantus; this combination reduces total insulin requirements by 20–30% and provides superior glycemic control. 1

• Metformin should not be discontinued when starting insulin unless contraindicated (e.g., renal impairment, acute illness) 1
• The combination of metformin plus basal insulin is explicitly endorsed by the American Diabetes Association 1
• Discontinue sulfonylureas when advancing beyond basal-only insulin to prevent additive hypoglycemia risk 3, 1

Hypoglycemia Management

• Treat any glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate (4 glucose tablets or 4 oz juice) 1
• Recheck glucose in 15 minutes and repeat treatment if needed 1
• If hypoglycemia occurs without an obvious cause, reduce the Lantus dose by 10–20% immediately before the next injection 1
• Provide comprehensive education on hypoglycemia recognition, treatment, and prevention 1

Special Populations

Elderly Patients (>65 years)

• Start with lower doses of 0.1–0.25 units/kg/day to minimize hypoglycemia risk due to increased insulin sensitivity 1
• Consider less stringent glycemic targets (HbA1c <8%) for those with limited life expectancy or multiple comorbidities 1

Renal Impairment

• Use lower starting doses of 0.1–0.25 units/kg/day in patients with eGFR <45 mL/min/1.73 m² 1
• For CKD stage 5, reduce total daily insulin by 50% for type 2 diabetes and 35–40% for type 1 diabetes 1
• Titrate conservatively and monitor closely for hypoglycemia, as insulin clearance decreases with declining kidney function 1

Hospitalized Patients

• For patients on high-dose home insulin (≥0.6 units/kg/day), reduce the total daily dose by 20% upon admission to prevent hypoglycemia 1
• For NPO or poor oral intake, administer 75–80% of the usual long-acting analog dose to maintain basal coverage while lowering hypoglycemia risk 1
• Never fully discontinue basal insulin in type 1 diabetes or insulin-dependent type 2 diabetes, even when NPO, to prevent diabetic ketoacidosis 1

Pregnancy

• While Lantus is used in pregnant women with diabetes, there is no definitive study confirming its benefits over NPH insulin 5
• Insulin requirements typically increase during pregnancy and drop dramatically postpartum (reduce by 50% immediately after delivery) 1

Twice-Daily Dosing Considerations

Lantus is typically administered once daily, but twice-daily dosing should be considered when once-daily administration fails to provide adequate 24-hour coverage. 1, 6

• Indications for splitting to twice daily include:

  • Persistent nocturnal hypoglycemia with morning hyperglycemia despite dose adjustments 6
  • Type 1 diabetes with high glycemic variability 1
  • Inadequate 24-hour coverage (glucose rising >50 mg/dL from bedtime to morning) 1
  • Very high total daily doses where injection volume becomes problematic 5

• When splitting, divide the total daily dose into two injections (e.g., morning and bedtime) rather than simply doubling the dose 6

Common Pitfalls to Avoid

• Never delay insulin initiation in patients not achieving glycemic goals with oral medications; prolonged hyperglycemia increases complication risk 1
• Never discontinue metformin when starting Lantus unless contraindicated; this leads to higher insulin requirements and more weight gain 1
• Never continue escalating Lantus beyond 0.5–1.0 units/kg/day without addressing postprandial hyperglycemia; this causes over-basalization with increased hypoglycemia and suboptimal control 1
• Never use Lantus to treat postprandial hyperglycemia; it provides basal coverage only and must be supplemented with rapid-acting insulin at mealtimes for glucose surges after meals 5
• Never mix Lantus with other insulins in the same syringe; it will coprecipitate short-acting insulins and alter absorption 5, 7
• Do not rely solely on correction (sliding-scale) insulin without scheduled basal coverage; this reactive approach is condemned by major diabetes guidelines 1

Expected Clinical Outcomes

• With proper titration, Lantus provides relatively constant basal insulin levels for approximately 24 hours without pronounced peaks 5, 8, 9
• The major advantage over NPH insulin is a lower frequency of hypoglycemic reactions, especially nocturnal episodes, while achieving equivalent glycemic control 5, 8, 9
• Basal insulin optimization alone can produce an HbA1c reduction of 1.5–2.0% 1
• Patients report higher treatment satisfaction with Lantus compared to NPH insulin due to once-daily dosing and reduced hypoglycemia 8
• The reproducibility of plasma insulin levels is improved with Lantus compared to NPH, allowing easier dose titration 7

Patient Education Essentials

• Teach proper injection technique and site rotation to prevent lipohypertrophy 1
• Provide education on hypoglycemia recognition and treatment (symptoms, <70 mg/dL threshold, 15-gram carbohydrate rule) 1
• Instruct on "sick day" management: continue insulin even if not eating, check glucose every 4 hours, maintain hydration 1
• Emphasize the importance of daily fasting glucose monitoring during titration 1
• Explain insulin storage and handling: store unopened vials/pens in refrigerator; once opened, can be kept at room temperature (36–86°F) for up to 28 days 1
• Provide a glucagon emergency kit and train family members on its use for severe hypoglycemia 1