What is the recommended dosing and administration of insulin glargine (long-acting insulin analog) for an adult or geriatric patient with diabetes, possibly alongside hypertension or heart failure?

Insulin Glargine Dosing and Administration

Initial Dosing for Type 2 Diabetes

For insulin-naive adults with type 2 diabetes, start insulin glargine at 10 units once daily OR 0.1-0.2 units/kg body weight, administered at the same time each day, and continue metformin unless contraindicated. 1, 2

• The FDA-approved starting dose is 0.2 units/kg or up to 10 units once daily for type 2 diabetes patients not currently on insulin 2
• For patients with severe hyperglycemia (A1C ≥9%, blood glucose ≥300-350 mg/dL), consider higher starting doses of 0.3-0.5 units/kg/day as total daily insulin using a basal-bolus regimen from the outset 1
• Administer subcutaneously into the abdominal area, thigh, or deltoid, rotating injection sites within the same region 2

Initial Dosing for Type 1 Diabetes

For type 1 diabetes, start with approximately one-third of the total daily insulin requirement as insulin glargine, with the remaining two-thirds provided as short-acting premeal insulin. 2

• Total daily insulin requirements typically range from 0.4-1.0 units/kg/day, with 0.5 units/kg/day being typical for metabolically stable patients 1
• Approximately 40-60% should be given as basal insulin (glargine) and 50-60% as prandial insulin divided among meals 1
• Insulin glargine must be used concomitantly with short-acting insulin in type 1 diabetes 2

Dose Titration Protocol

Increase insulin glargine by 2 units every 3 days if fasting glucose is 140-179 mg/dL, or by 4 units every 3 days if fasting glucose is ≥180 mg/dL, until reaching target fasting glucose of 80-130 mg/dL. 1

• If hypoglycemia occurs without clear cause, reduce the dose by 10-20% immediately 1
• If more than 2 fasting glucose values per week are <80 mg/dL, decrease the dose by 2 units 1
• Daily fasting blood glucose monitoring is essential during titration 1

Critical Threshold: When to Add Prandial Insulin

When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone to prevent "overbasalization." 1

• Clinical signals of overbasalization include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia episodes, and high glucose variability 1
• Start prandial insulin with 4 units of rapid-acting insulin before the largest meal, or use 10% of the current basal dose 1
• Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on 2-hour postprandial glucose readings 1

Special Populations

Elderly Patients (≥65 years)

In elderly patients, administer insulin glargine in the morning rather than at bedtime to reduce nocturnal hypoglycemia risk, and use conservative starting doses of 0.1-0.15 units/kg/day. 3, 4

• Target fasting glucose of 90-150 mg/dL rather than the standard 80-130 mg/dL 4
• Increase dose by only 2 units if ≥50% of fasting values are above goal 4
• Decrease dose by 2 units if >2 fasting values/week are <80 mg/dL 4
• Hypoglycemia may be difficult to recognize in geriatric patients 2

Hospitalized Patients

For hospitalized patients with reduced oral intake, start with a lower total daily dose of 0.1-0.15 units/kg/day, given mainly as basal insulin. 3

• 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
• Additional rapid-acting insulin analogs should be administered as correctional insulin for glucose levels >180 mg/dL before meals and at bedtime 3
• Noninsulin antihyperglycemic agents are not recommended for hospitalized patients 3

Patients with Renal or Hepatic Impairment

Frequent glucose monitoring and dose adjustment are necessary in patients with renal or hepatic impairment due to increased hypoglycemia risk. 2

• For CKD stage 5 with type 2 diabetes, reduce total daily insulin dose by 50% 1
• For CKD stage 5 with type 1 diabetes, reduce total daily insulin dose by 35-40% 1

Administration Guidelines

Administer insulin glargine subcutaneously once daily at the same time every day; do not administer intravenously, via insulin pump, or mix with other insulins. 2

• The solution must be clear and colorless with no visible particles 2
• Rotate injection sites within the same region to reduce risk of lipodystrophy and localized cutaneous amyloidosis 2
• Do not inject into areas of lipodystrophy or localized cutaneous amyloidosis 2

Switching from Other Insulins

When switching from twice-daily NPH insulin to once-daily insulin glargine, start with 80% of the total NPH dosage being discontinued. 2

• When switching from once-daily NPH insulin, use the same dosage 2
• When switching from TOUJEO (insulin glargine 300 units/mL), start with 80% of the TOUJEO dosage 2

Twice-Daily Dosing Considerations

Consider twice-daily insulin glargine dosing when once-daily administration fails to provide adequate 24-hour coverage, particularly in type 1 diabetes with high glycemic variability. 1, 5

• Indications include: inadequate 24-hour coverage, persistent nocturnal hypoglycemia with morning hyperglycemia, or refractory glycemic patterns 1
• This approach may be necessary in labile type 1 diabetes or obese, insulin-resistant patients requiring high insulin volumes 6

Common Pitfalls to Avoid

• Never delay insulin initiation in patients not achieving glycemic goals with oral medications, as this prolongs hyperglycemia exposure 1
• Never discontinue metformin when starting insulin unless contraindicated, as the combination provides superior control with less weight gain 1
• Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this causes overbasalization with increased hypoglycemia risk 1
• Never use sliding scale insulin as monotherapy in hospitalized patients; always provide scheduled basal insulin 1
• Never mix or dilute insulin glargine with any other insulin or solution due to its acidic pH 3, 2

Monitoring Requirements

• Check fasting blood glucose daily during titration phase 1, 4
• Increase frequency of blood glucose monitoring during any insulin regimen changes 2
• Reassess every 3 days during active titration and every 3-6 months once stable 1
• Monitor for signs of overbasalization at each clinical visit 1