In a 71‑kg (156‑lb) woman with BMI 29.5, blood pressure 110/70 mm Hg, heart rate 70 bpm, respiratory rate 22/min, temperature 97.4 °F, oxygen saturation 96%, undergoing chemotherapy every 2 weeks and currently on insulin glargine (Lantus) 16 units nightly with glucose readings around 300 mg/dL, how should I start a rapid‑acting insulin such as insulin aspart (Novolog) and what initial dosing regimen is recommended?

Starting Rapid-Acting Insulin in a Patient on Basal Insulin with Persistent Hyperglycemia

Start insulin aspart (Novolog) 4 units before the largest meal or the meal with the greatest postprandial glucose excursion, and consider reducing the Lantus dose by 10% (from 16 to 14-15 units) if A1C is less than 8%. 11

Initial Dosing Strategy

Given glucose readings around 300 mg/dL despite 16 units of basal insulin nightly, this patient requires prandial insulin intensification. The 2025 ADA Standards of Care provide clear guidance:

Step 1: Add Single Prandial Dose

• Start with 4 units of rapid-acting insulin (Novolog/aspart) before one meal 11
• Alternative calculation: 10% of current basal dose = 1.6 units, rounded to 2 units (though 4 units is the standard recommendation) 11
• Target the largest meal or the meal causing the highest postprandial glucose spike 11

Step 2: Adjust Basal Insulin

• If A1C <8%: reduce basal insulin by 4 units or 10% (from 16 to 12-14 units) 1
• If A1C ≥8%: maintain current basal dose initially 1
• This prevents overbasalization and reduces hypoglycemia risk

Titration Protocol

Increase prandial insulin by 1-2 units or 10-15% every 2-3 days based on premeal glucose readings: 12

• If premeal glucose >140 mg/dL: increase the previous meal's insulin dose by 10-20%
• If premeal glucose <70 mg/dL: decrease the previous meal's insulin dose by 10-20%
• Target premeal glucose: <110-140 mg/dL 2

Progression if Goals Not Met

If A1C remains above goal after optimizing one prandial dose:

1. Add a second prandial dose before the next largest meal (start with 4 units)
2. Progress to full basal-bolus (insulin before all three meals) if needed 11
3. Each prandial dose is titrated independently based on the subsequent premeal glucose

Critical Considerations for This Patient

Chemotherapy Context

• Corticosteroid-induced hyperglycemia is common with chemotherapy regimens
• Glucose patterns may fluctuate with treatment cycles (every 2 weeks in this case)
• More frequent monitoring during and after chemotherapy infusions is essential
• Consider whether hyperglycemia is primarily fasting (basal issue) vs. postprandial (prandial issue)

Signs of Overbasalization

Watch for these signals that indicate need for prandial rather than more basal insulin: 11

• Bedtime-to-morning glucose differential >50 mg/dL
• Basal dose >0.5 units/kg/day (this patient: 16 units ÷ 70.76 kg = 0.23 units/kg - still room to increase basal)
• Hypoglycemia with continued hyperglycemia
• High glucose variability

Alternative Consideration

Before adding prandial insulin, ensure basal insulin is optimized: The current dose of 16 units (0.23 units/kg) is relatively modest. The 2025 ADA guidelines recommend starting basal at 0.1-0.2 units/kg and titrating by 2 units every 3 days until fasting glucose is controlled. 11 With glucose at 300 mg/dL, you could:

1. First optimize basal insulin by increasing Lantus by 2 units every 3 days until fasting glucose <130 mg/dL
2. Then add prandial insulin if postprandial or overall glycemic control remains inadequate

However, given the severity of hyperglycemia (≥300 mg/dL), the 2023 AACE guidelines support starting both basal and prandial insulin simultaneously in this scenario. 2

Practical Implementation

Recommended approach for this patient:

• Increase Lantus to 18-20 units nightly (titrate by 2 units every 3 days targeting fasting glucose <130 mg/dL)
• Start Novolog 4 units before dinner (typically the largest meal)
• Monitor premeal glucose before each meal and at bedtime
• Titrate Novolog by 1-2 units every 2-3 days based on the next premeal glucose reading
• Prescribe glucagon for emergency hypoglycemia management 1

Hypoglycemia Management Protocol

If blood glucose <70 mg/dL: 11

• Determine cause (missed meal, increased activity, excessive dose)
• If no clear reason: reduce the corresponding insulin dose by 10-20%
• If blood glucose <40 mg/dL: reduce dose by 20-40% 2

This stepwise approach balances aggressive glucose control (critical given readings of 300 mg/dL) with safety, particularly important in a patient undergoing chemotherapy who may have variable appetite and increased infection risk from hyperglycemia.