For a female patient weighing 43 kg with a hemoglobin A1c of 13 % and normal renal function who is started on insulin glargine (100 units/mL), how many milliliters of insulin should be administered, how often should it be given each day, and which oral antidiabetic agents should be added?

Insulin Glargine Dosing and Adjunctive Therapy

Start with 10 units (0.1 mL) of insulin glargine 100 units/mL subcutaneously once daily at the same time each day, and add a GLP-1 receptor agonist as your primary oral/injectable adjunctive therapy. 1, 2

Initial Insulin Dosing

For your 43 kg patient with HbA1c of 13%, you have two evidence-based starting options:

• Conservative approach: 10 units once daily (0.1 mL of the 100 units/mL formulation) 1, 2
• Weight-based approach: 0.1-0.2 units/kg/day = 4.3-8.6 units, which rounds to approximately 5-10 units once daily 1, 2

Given the severely elevated HbA1c of 13%, I recommend starting at 10 units (0.1 mL) once daily. This provides adequate initial glycemic control while minimizing hypoglycemia risk in this low-weight patient. The FDA label and 2025 ADA guidelines both support this conservative 10-unit starting dose for type 2 diabetes patients not currently on insulin 2.

Dosing Frequency

Administer once daily at the same time every day - this is non-negotiable for insulin glargine 2. The timing can be any time of day, but consistency is critical for stable basal coverage.

Volume Calculation

• 10 units ÷ 100 units/mL = 0.1 mL per injection
• As you titrate upward, each 10-unit increase = 0.1 mL increase

Titration Strategy

Increase by 2 units every 3 days until fasting plasma glucose reaches 80-130 mg/dL without hypoglycemia 1. This is the evidence-based titration algorithm from the 2025 ADA Standards of Care.

Key titration principles:

• Set a clear fasting plasma glucose target (typically 80-130 mg/dL)
• Patient should check fasting glucose daily during titration
• If hypoglycemia occurs without clear cause, reduce dose by 10-20% 1
• Maximum doses can reach 0.5-1.0 units/kg/day (22-43 units for this patient) before considering intensification 3

Adjunctive Antidiabetic Therapy

Add a GLP-1 receptor agonist (semaglutide, dulaglutide, or liraglutide) as first-line adjunctive therapy 1. The 2025 ADA guidelines explicitly prioritize GLP-1 RAs when HbA1c remains above goal on basal insulin, particularly before considering prandial insulin intensification.

Why GLP-1 RA First?

• Superior cardiovascular and renal protection compared to other oral agents
• Reduces postprandial glucose excursions that basal insulin doesn't address
• Mitigates insulin-associated weight gain (critical in a 43 kg patient where further weight loss would be concerning)
• Can use fixed-ratio combination products (iGlarLixi or IDegLira) if appropriate 1

Alternative Oral Agents

If GLP-1 RA is contraindicated or not tolerated:

• Metformin: Continue or add if not already prescribed (reduces insulin dose requirements and weight gain) 4
• SGLT2 inhibitors: Consider for additional cardiovascular/renal benefits if appropriate

Do not abruptly discontinue existing oral medications when starting insulin - this causes rebound hyperglycemia 4.

Critical Monitoring Points

Watch for Overbasalization

If you find yourself continuously escalating basal insulin beyond 0.5 units/kg/day (~22 units) without meaningful fasting glucose improvement:

• Stop increasing basal insulin
• Add GLP-1 RA if not already prescribed 1
• Consider adding prandial insulin with the largest meal (start 4 units or 10% of basal dose) 1

Hypoglycemia Management

• Prescribe glucagon for emergency use 1
• If hypoglycemia occurs, reduce dose by 10-20% 1
• Increase glucose monitoring frequency during titration 2

Injection Technique

• Rotate sites within same region (abdomen, thigh, or deltoid) 2
• Avoid lipodystrophy areas - can cause erratic absorption and hypoglycemia 2

Common Pitfalls to Avoid

1. Don't mix or dilute insulin glargine - it must be given alone 2
2. Don't give intravenously or via pump - subcutaneous only 2
3. Don't continue escalating basal insulin indefinitely - recognize overbasalization and add adjunctive agents 1
4. Don't forget to address postprandial hyperglycemia - basal insulin only controls fasting glucose; with HbA1c of 13%, this patient will need postprandial coverage via GLP-1 RA or eventual prandial insulin 1