Is it safe to administer a single 90‑unit dose of Lantus (insulin glargine)?

Can You Take 90 Units of Lantus at One Time?

Yes, a single 90‑unit dose of Lantus (insulin glargine) can be administered safely when clinically indicated, because there is no absolute maximum dose for insulin glargine—dosing is individualized based on metabolic needs, body weight, insulin resistance, and concurrent medications. 1

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Evidence Supporting High‑Dose Basal Insulin

• The FDA does not impose a maximum dose for insulin glargine; dosing is individualized according to metabolic needs, body weight, illness severity, and concomitant medications, and can exceed 1 unit/kg/day in severe insulin resistance or acute illness. 1
• Patients with type 2 diabetes often require ≥1 unit/kg/day due to insulin resistance, meaning a 90‑kg (≈200‑lb) adult may need ≥90 units of basal insulin daily. 1, 2
• In hospitalized patients with severe hyperglycemia, total daily insulin doses of 0.3–0.5 units/kg/day are recommended, with approximately 50 % allocated to basal insulin—for a 180‑kg patient, this translates to ≈27–45 units of basal insulin, but higher doses are frequently required in practice. 1
• When basal insulin exceeds 0.5 units/kg/day (e.g., 45 units for a 90‑kg patient) without achieving glycemic targets, guidelines recommend adding prandial insulin or a GLP‑1 receptor agonist rather than further basal escalation to avoid "over‑basalization." 1, 2

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Practical Considerations for 90‑Unit Doses

Injection Volume and Comfort

• U‑100 insulin glargine (Lantus) delivers 100 units per mL, so a 90‑unit dose equals 0.9 mL—a volume that is well tolerated in a single subcutaneous injection. 2
• For patients requiring even larger doses (>100 units), U‑300 insulin glargine (Toujeo) reduces injection volume by delivering 300 units per mL, improving comfort without compromising efficacy. 2, 3

Absorption and Duration

• Insulin glargine forms amorphous microprecipitates in subcutaneous tissue (pH >7.4), from which insulin is gradually released over approximately 24 hours, providing a relatively constant basal insulin supply without pronounced peaks. 4, 5
• The peakless profile of insulin glargine allows once‑daily dosing at any time of day (preferably at the same time daily), and the pharmacokinetic properties support doses well above 90 units when clinically necessary. 4, 5, 6

When to Consider Twice‑Daily Dosing

• In some patients, glargine may not last 24 hours, and dividing the dose into two daily injections should be considered—for example, splitting 90 units into 45 units twice daily. 2, 7
• Twice‑daily dosing is particularly useful in type 1 diabetes with high glycemic variability, patients requiring high basal insulin doses, or those with refractory hypoglycemia despite optimized once‑daily regimens. 1, 7
• A case report demonstrated that a patient with morning hypoglycemia on once‑daily glargine achieved resolution of hypoglycemia by switching to a twice‑daily regimen, despite no improvement with dose titration or timing changes. 7

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Critical Thresholds and Warning Signs

Over‑Basalization

• Basal insulin dose >0.5 units/kg/day without achieving glycemic targets signals the need to add prandial insulin or a GLP‑1 receptor agonist rather than continuing basal escalation. 1, 2
• Clinical signs of over‑basalization include:
  • Bedtime‑to‑morning glucose differential ≥50 mg/dL
  • Episodes of hypoglycemia despite overall hyperglycemia
  • High glucose variability throughout the day 1

Hypoglycemia Management

• If any unexplained hypoglycemia (glucose <70 mg/dL) occurs, reduce the basal insulin dose by 10–20 % immediately before the next administration. 1
• Treat glucose <70 mg/dL with 15 g of fast‑acting carbohydrate, recheck in 15 minutes, and repeat if needed. 1

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Monitoring Requirements

• Daily fasting glucose checks are essential during titration to guide basal insulin adjustments. 1, 2
• Target fasting glucose range: 80–130 mg/dL. 1
• If fasting glucose remains ≥180 mg/dL, increase the basal dose by 4 units every 3 days; if fasting glucose is 140–179 mg/dL, increase by 2 units every 3 days. 1

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Common Pitfalls to Avoid

• Do not delay insulin initiation or prescribe inadequate doses in patients with severe hyperglycemia; immediate basal‑bolus therapy is required when fasting glucose exceeds 180 mg/dL despite oral agents. 1
• Do not continue escalating basal insulin beyond 0.5–1.0 units/kg/day without addressing post‑prandial hyperglycemia, as this leads to over‑basalization with increased hypoglycemia risk and suboptimal control. 1, 2
• Do not mix insulin glargine with any other insulin or solution due to its low pH (≈4.0), which would alter its pharmacokinetic profile; when basal and prandial insulin are required together, administer as separate injections. 1, 2

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Special Populations

High‑Dose Insulin Users

• Patients requiring large basal insulin doses benefit from reduced injection volume when using the more concentrated U‑300 formulation (Toujeo), improving injection comfort without compromising efficacy. 2, 3
• U‑300 glargine (Toujeo) is not bioequivalent to U‑100 glargine (Lantus); unit‑for‑unit conversion is inappropriate, and clinicians should adjust the basal dose and reinforce glucose monitoring when patients switch formulations. 3

Hospitalized Patients

• For hospitalized patients on high‑dose home insulin (≥0.6 units/kg/day), reduce the total daily dose by 20 % upon admission to prevent hypoglycemia. 1
• In elderly patients (>65 years), those with renal impairment, or poor oral intake, use lower starting doses of 0.1–0.25 units/kg/day to minimize hypoglycemia risk. 1

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Conclusion

A single 90‑unit dose of Lantus is safe and appropriate when clinically indicated, particularly in patients with severe insulin resistance or type 2 diabetes requiring high basal insulin doses. 1, 2 The key is to ensure proper monitoring, recognize signs of over‑basalization, and add prandial insulin or a GLP‑1 receptor agonist when basal insulin exceeds 0.5 units/kg/day without achieving glycemic targets. 1, 2