For a 45‑year‑old Hispanic male with newly diagnosed diabetes (A1C 14.5 %), creatinine 0.68 mg/dL, eGFR >90 mL/min/1.73 m², weight 98.4 kg, not in diabetic ketoacidosis, and recent insulin drip rates of 2, 2, 3, 2, 2, 3 units over the past 6 hours, what should his once‑daily basal insulin (insulin glargine, Lantus) dose, insulin‑sensitivity factor, and insulin‑to‑carbohydrate ratio be?

Basal Insulin Dosing for Newly Diagnosed Type 2 Diabetes

For this patient, initiate Lantus at 20 units once daily at bedtime, with an insulin sensitivity factor (ISF) of 1:50 and an insulin-to-carbohydrate ratio (ICR) of 1:10.

Rationale for Basal Insulin Dose

Your patient's insulin drip averaged 2.3 units/hour over the past 6 hours, totaling approximately 14 units over that period. Extrapolated to 24 hours, this suggests a total daily insulin requirement of approximately 55 units. However, since he is not in DKA and has newly diagnosed type 2 diabetes with preserved renal function, we should use a more conservative conversion approach 1, 2.

Calculation Method:

• Total daily insulin requirement estimate: 0.2 units/kg × 98.4 kg = 19.7 units/day
• Basal insulin component: Approximately 50% of total daily dose = ~10 units
• However, given his recent insulin drip requirements and A1C of 14.5%, start at the higher end: 20 units once daily

The ADA 2025 guidelines recommend starting basal insulin at either 10 units per day OR 0.1-0.2 units/kg per day 1. The FDA label for Lantus specifically states that for type 2 diabetes patients not currently on insulin, the recommended starting dose is 10 units (or 0.2 units/kg) once daily 2. Given his significant hyperglycemia (A1C 14.5%) and recent insulin requirements on drip, starting at 0.2 units/kg (approximately 20 units) is appropriate.

Insulin Sensitivity Factor (ISF)

Use the "1500 Rule" for rapid-acting insulin or "1800 Rule" for regular insulin:

• 1500 ÷ estimated total daily insulin dose (50 units) = 1:30
• However, for newly diagnosed patients with preserved renal function and to minimize hypoglycemia risk, start more conservatively at 1:50

This means 1 unit of rapid-acting insulin will lower blood glucose by approximately 50 mg/dL.

Insulin-to-Carbohydrate Ratio (ICR)

Use the "500 Rule":

• 500 ÷ estimated total daily insulin dose (50 units) = 1:10

This means 1 unit of rapid-acting insulin covers 10 grams of carbohydrate.

Titration Strategy

Following ADA 2025 guidelines 1:

• Set fasting plasma glucose goal: 80-130 mg/dL
• Titration algorithm: Increase Lantus by 2 units every 3 days until fasting glucose reaches goal without hypoglycemia
• For hypoglycemia: If blood glucose <70 mg/dL without clear cause, reduce dose by 10-20% (2-4 units)
• Reassess every 3-6 months to avoid therapeutic inertia

Important Considerations

Renal Function

His eGFR >90 mL/min/1.73 m² is excellent, requiring no dose adjustment 2, 3. Insulin glargine has not been extensively studied in renal impairment, but his normal kidney function eliminates this concern.

Timing and Administration

• Administer Lantus once daily at the same time each day (typically bedtime) 2
• Do NOT mix with other insulins - Lantus must be given separately 2
• Rotate injection sites within the same region (abdomen, thigh, or deltoid) 2

Common Pitfalls to Avoid

1. Do not use Lantus intravenously - the usual subcutaneous dose given IV could cause severe hypoglycemia 2
2. Do not dilute or mix Lantus with any other insulin or solution 2
3. Monitor for nocturnal hypoglycemia - although Lantus has a flat profile, risk exists in the first 4 weeks 4
4. Ensure basal insulin is never stopped - even if patient becomes NPO, continue basal insulin (unlike prandial insulin) 5

Prandial Insulin Coverage

If adding mealtime insulin becomes necessary (if A1C remains >7% after basal optimization):

• Start with 4 units of rapid-acting insulin before the largest meal 1
• Alternatively, use 10% of basal dose (2 units in this case, though 4 units is more practical)
• Titrate by 1-2 units or 10-15% based on postprandial glucose readings 1

Monitoring Requirements

• Daily fasting glucose for titration
• Pre-meal and 2-hour postprandial glucose if adding prandial insulin
• A1C every 3 months until at goal, then every 6 months 1
• Prescribe glucagon for emergency hypoglycemia treatment 1

This approach balances aggressive glycemic control (given his A1C of 14.5%) with safety, using evidence-based starting doses and titration algorithms that minimize hypoglycemia risk while achieving target glucose levels 1, 2.