How should insulin be dosed in an NBM (nothing by mouth) patient with HbA1c (glycated hemoglobin) of 10% and random blood glucose (RBS) of 400 mg/dL?

Insulin Management in NBM Patient with HbA1c 10% and RBS 400 mg/dL

For an NBM (nothing by mouth) patient with severe hyperglycemia (HbA1c 10%, RBS 400 mg/dL), initiate basal insulin ONLY at 0.5 U/kg/day given as a single daily dose, plus correctional insulin every 4-6 hours using rapid-acting insulin analogs. Do NOT give prandial insulin since the patient is not eating.

Initial Insulin Dosing Algorithm

Step 1: Calculate Total Daily Dose (TDD)

For this patient with RBS 400 mg/dL (within the 201-400 mg/dL range) and HbA1c >10%, start with 0.5 U/kg/day 1. This represents the upper end of the recommended range given the severe hyperglycemia.

Important caveat: Reduce to 0.2-0.3 U/kg/day if the patient is:

• Age ≥70 years
• GFR <60 mL/min
• Frail or malnourished 1

Step 2: Distribute the Insulin Dose

Since the patient is NBM:

• 100% of TDD = Basal insulin (glargine once daily or detemir/NPH twice daily)
• 0% prandial insulin (hold completely - patient not eating) 1

For example, in a 70 kg patient without contraindications:

• TDD = 70 kg × 0.5 U/kg = 35 units
• Give 35 units of basal insulin (glargine once daily at same time each day, OR detemir/NPH 17-18 units twice daily)

Step 3: Add Correctional (Supplemental) Insulin

Critical for NBM patients: Add correctional doses using the "insulin-sensitive" or "usual" column depending on patient factors 1:

• Rapid-acting insulin analog: Every 4-6 hours
• Regular insulin: Every 6 hours (at 6-12-6-12 schedule)

Use the insulin-sensitive column for:

• Elderly patients
• Those not eating
• Impaired renal function 1

Correctional Scale (from Endocrine Society Guidelines):

Blood Glucose (mg/dL)	Insulin-Sensitive	Usual	Insulin-Resistant
141-180	2 units	4 units	6 units
181-220	4 units	6 units	8 units
221-260	6 units	8 units	10 units
261-300	8 units	10 units	12 units
301-350	10 units	12 units	14 units
351-400	12 units	14 units	16 units
≥400	14 units	16 units	18 units

For your patient with RBS 400 mg/dL, start with 14 units (insulin-sensitive) or 16 units (usual) of rapid-acting insulin immediately 1.

Ongoing Management

Monitoring Schedule

• Check blood glucose every 4-6 hours (before scheduled correctional doses)
• Adjust basal insulin based on fasting/morning glucose trends
• Continue correctional insulin at each check 1

Titration Strategy

For persistent hyperglycemia (≥2 readings ≥180 mg/dL in 24 hours):

• Increase basal insulin by 10-20% every 1-3 days
• If requiring >24 units of correctional insulin in 24 hours, add that total to the next day's basal dose 1, 2

For hypoglycemia:

• BG <70 mg/dL: Reduce basal by 10-20%
• BG <40 mg/dL: Reduce basal by 20-40% 3

Critical Pitfalls to Avoid

1. Never use sliding-scale insulin (SSI) alone - this results in 3-fold increased risk of hyperglycemia >200 mg/dL and poor outcomes 1

2. Do NOT give prandial insulin to NBM patients - this causes severe hypoglycemia. Only basal + correctional insulin 1

3. If patient starts eating: Immediately restart prandial insulin at 50% of original TDD divided into three pre-meal doses, while continuing basal insulin 1

4. Discontinue oral diabetes medications on admission - they are contraindicated in acute illness and NBM status 1

5. Watch for glucose toxicity resolution - as hyperglycemia improves over days, insulin requirements may DROP significantly, requiring dose reductions to prevent hypoglycemia 3

When to Intensify

The severe hyperglycemia (HbA1c >10%, BG ≥300 mg/dL) indicates glucose toxicity that requires prompt reduction 3. If basal + correctional insulin fails to achieve BG <180 mg/dL within 24-48 hours, consider:

• Increasing basal insulin more aggressively (by 20% daily)
• Consulting endocrinology for possible insulin infusion if critically ill 3

Once eating resumes: Transition to full basal-bolus regimen with 50% basal and 50% prandial (divided into three pre-meal doses), maintaining correctional insulin at all times 1.