What are the guidelines for initiating long-acting insulin (e.g. glargine (insulin glargine) or detemir (insulin detemir)) therapy?

Initiating Long-Acting Insulin Therapy

Starting Dose

For insulin-naive patients with type 2 diabetes, start with 10 units once daily or 0.1-0.2 units/kg/day of long-acting insulin (glargine or detemir), administered at the same time each day. 1

• For a typical adult patient, 10 units once daily is the standard starting dose 1
• Higher starting doses of 0.3-0.5 units/kg/day should be considered for patients with severe hyperglycemia (A1C ≥9%, blood glucose ≥300-350 mg/dL, or symptomatic/catabolic features) 1, 2
• For type 1 diabetes, total daily insulin requirements typically range from 0.4-1.0 units/kg/day, with approximately 50% as basal insulin 1, 3

Timing of Administration

Administer long-acting insulin at the same time each day to maintain stable blood glucose levels. 3

• Glargine is typically given once daily, often at bedtime 4
• Detemir may require twice-daily dosing when once-daily administration fails to provide 24-hour coverage 2, 3

Dose Titration Protocol

Increase the basal insulin dose by 2-4 units (or 10-15%) every 3 days until fasting blood glucose reaches 80-130 mg/dL. 1

Specific Titration Algorithm:

• If fasting glucose ≥180 mg/dL: increase by 4 units every 3 days 1
• If fasting glucose 140-179 mg/dL: increase by 2 units every 3 days 1
• If >2 fasting glucose values per week are <80 mg/dL: decrease dose by 2 units 2
• If hypoglycemia occurs: reduce dose by 10-20% 1

Foundation Therapy

Continue metformin when initiating insulin unless contraindicated, as it reduces weight gain, lowers insulin requirements, and decreases hypoglycemia risk. 5, 1

• Do not abruptly discontinue oral medications when starting insulin due to risk of rebound hyperglycemia 5

When to Add Prandial Insulin

Add prandial insulin when basal insulin has been optimized (fasting glucose 80-130 mg/dL) but A1C remains above target after 3-6 months, or when basal insulin dose approaches 0.5-1.0 units/kg/day without achieving glycemic goals. 1, 2

Signs of Overbasalization (indicating need for prandial insulin):

• Basal dose >0.5 units/kg/day 1
• High bedtime-to-morning glucose differential (≥50 mg/dL) 1
• Hypoglycemia episodes 1
• High glucose variability 1

Starting Prandial Insulin:

• Begin with 4 units of rapid-acting insulin before the largest meal, or use 10% of the basal dose 2, 1
• Titrate by 1-2 units every 3 days based on pre-meal and 2-hour postprandial glucose readings 1

Monitoring Requirements

Daily fasting blood glucose monitoring is essential during the titration phase. 1

• Monitor fasting glucose daily during active titration 1
• Reassess every 3 days during active titration and every 3-6 months once stable 1
• Set individualized fasting plasma glucose goals (typically 80-130 mg/dL for most adults, 90-150 mg/dL for older adults) 2, 1

Special Populations

Older Adults:

• Use more conservative targets (fasting glucose 90-150 mg/dL) 2
• Once-daily basal insulin is associated with minimal side effects and is a reasonable option 2
• Consider lower starting doses (0.1-0.25 units/kg/day) for high-risk patients including elderly, those with renal failure, or poor oral intake 1

Hospitalized Patients:

• For insulin-naive hospitalized patients, start with 0.3-0.5 units/kg/day total daily dose, with half as basal insulin 1
• For patients on high-dose home insulin (≥0.6 units/kg/day), reduce total daily dose by 20% to prevent hypoglycemia 1

Critical Pitfalls to Avoid

Do not delay insulin initiation in patients not achieving glycemic goals with oral medications—this causes harm. 1

• Avoid continuing to escalate basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to suboptimal control and increased hypoglycemia risk 1
• Do not ignore the need for prandial insulin when basal insulin exceeds 0.5 units/kg/day and A1C remains elevated 2, 1
• Never dilute or mix insulin glargine with other insulins due to its low pH 1, 3
• Avoid intramuscular injection of long-acting insulin, as severe hypoglycemia may result 5
• Rotate injection sites continuously within a given area to prevent lipodystrophy, which delays insulin absorption 6, 5

Patient Education Essentials

Educate patients on proper injection technique, site rotation, hypoglycemia recognition and treatment, and "sick day" management rules. 1

• Teach recognition and treatment of hypoglycemia symptoms 1
• Instruct on self-monitoring of blood glucose 1
• Emphasize consistent timing of daily administration 3
• Warn about early symptoms of hyperglycemia (nausea, vomiting, drowsiness, flushed dry skin, increased urination, thirst) 6