How should I adjust basal (long‑acting), bolus (rapid‑acting), premixed, and NPH insulin doses based on fasting and pre‑meal blood glucose levels?

Adjusting Insulin Doses Based on Blood Glucose and Insulin Type

Basal (Long-Acting) Insulin Adjustment

For patients on basal insulin (glargine, detemir, degludec, NPH), titrate based on fasting glucose values using a systematic 3-day protocol. 1

Standard Titration Algorithm

• Start basal insulin at 10 units once daily or 0.1–0.2 units/kg/day for insulin-naïve type 2 diabetes patients 1, 2
• Increase by 2 units every 3 days if fasting glucose is 140–179 mg/dL 1
• Increase by 4 units every 3 days if fasting glucose is ≥180 mg/dL 1
• Target fasting glucose: 80–130 mg/dL 1
• Reduce dose by 10–20% immediately if any glucose reading falls below 70 mg/dL 1

Critical Threshold: When to Stop Basal Escalation

When basal insulin reaches 0.5–1.0 units/kg/day without achieving glycemic targets, stop further basal increases and add prandial insulin or a GLP-1 receptor agonist instead. 1, 2 Continuing to escalate basal insulin beyond this threshold leads to "over-basalization" with increased hypoglycemia risk and suboptimal control. 1, 2

Clinical signals of over-basalization include: 1, 2

• Basal dose >0.5 units/kg/day
• Bedtime-to-morning glucose differential ≥50 mg/dL
• Episodes of hypoglycemia despite overall hyperglycemia
• High glucose variability throughout the day

NPH-Specific Considerations

• NPH requires twice-daily dosing in most patients due to its shorter duration of action (12–16 hours) 1, 3
• Administer NPH at breakfast and bedtime to provide adequate 24-hour coverage 1, 3
• When converting from once-daily long-acting insulin to NPH, split the total dose as two-thirds in the morning and one-third at bedtime 1

Bolus (Rapid-Acting) Insulin Adjustment

For patients on rapid-acting insulin (lispro, aspart, glulisine), adjust each meal dose independently based on 2-hour post-prandial glucose values using a 3-day titration cycle. 1

Initiation and Titration Protocol

• Start with 4 units before the largest meal or 10% of the current basal dose 1, 2
• Administer 0–15 minutes before meals for optimal post-prandial control 1
• Increase each meal dose by 1–2 units (10–15%) every 3 days based on 2-hour post-prandial glucose 1
• Target post-prandial glucose: <180 mg/dL 1
• Reduce the implicated dose by 10–20% if hypoglycemia occurs 1

Correction (Supplemental) Dosing

• Add 2 units for pre-meal glucose >250 mg/dL 1
• Add 4 units for pre-meal glucose >350 mg/dL 1
• Correction insulin must supplement—not replace—scheduled prandial doses 1

Carbohydrate-Based Dosing (Advanced)

• Calculate insulin-to-carbohydrate ratio (ICR) as 450 ÷ total daily insulin dose 1
• Example: 45 units total daily dose → ICR of 1 unit per 10 grams carbohydrate 1
• Adjust ICR if post-prandial glucose consistently misses target 1

Premixed Insulin (70/30,75/25,50/50) Adjustment

Premixed insulin provides both basal and prandial coverage with fixed ratios, requiring consistent meal timing and carbohydrate intake. 4, 5

Initiation from Basal-Bolus Regimen

• Calculate total daily dose from current regimen 4
• Reduce total by 20% if current dose exceeds 0.6 units/kg/day 4
• Distribute as two-thirds before breakfast, one-third before dinner 4, 5
• Administer 30 minutes before meals (for human insulin 70/30) 4

Titration Protocol

• Adjust doses every 2 weeks based on fasting glucose patterns 1, 4
• Target fasting glucose: 90–150 mg/dL 1
• If ≥50% of fasting values exceed goal: increase dose by 2 units 1
• If >2 fasting values per week are <80 mg/dL: decrease dose by 2 units 1

Critical Limitations

Premixed insulin is contraindicated in hospitalized patients due to 64% hypoglycemia rates versus 24% with basal-bolus therapy. 5 Avoid in patients with: 4, 5

• Irregular meal timing or variable carbohydrate intake
• Need for maximal dosing flexibility
• Acute illness or hospitalization

NPH Insulin-Specific Adjustment

NPH insulin requires twice-daily administration in most patients and has a pronounced peak at 4–10 hours after injection. 1, 3

Dosing Schedule

• Administer before breakfast and at bedtime 1, 3
• For patients on enteral/parenteral feeding: start with 5 units every 12 hours 2
• Adjust based on pre-lunch glucose (for morning dose) and fasting glucose (for bedtime dose) 1, 3

Conversion from Long-Acting Insulin

• When switching from once-daily glargine to NPH, use two-thirds of the glargine dose in the morning and one-third at bedtime 1
• Monitor closely for hypoglycemia during the first week of conversion 1

Special Clinical Situations

Hospitalized Patients (Non-Critical Care)

• Start with 0.3–0.5 units/kg/day total insulin (50% basal, 50% prandial) 1
• For high-risk patients (age >65, renal impairment, poor intake): use 0.1–0.25 units/kg/day 1
• Check glucose before each meal and at bedtime (minimum 4 times daily) 1
• Never use sliding-scale insulin as monotherapy—it achieves target glucose in only 38% versus 68% with basal-bolus therapy 1

Steroid-Induced Hyperglycemia

• Increase prandial and correction insulin by 40–60% in addition to basal insulin 1
• Focus increases on lunch and dinner doses when morning prednisone is used 1
• Consider adding morning NPH to align with steroid peak effect 1

Patients with Renal Impairment

• For CKD Stage 5: reduce total daily insulin by 50% (type 2 diabetes) or 35–40% (type 1 diabetes) 1
• Use lower starting doses (0.1–0.25 units/kg/day) and titrate conservatively 1
• Monitor glucose more frequently due to prolonged insulin action 1

Perioperative Management

• Reduce basal insulin by 25% the evening before surgery 1
• Continue basal insulin even when NPO—never completely withhold 1
• Monitor glucose every 2–4 hours perioperatively 1
• Target glucose 80–180 mg/dL 1

Monitoring Requirements

Daily Monitoring During Titration

• Fasting glucose daily to guide basal insulin adjustments 1
• Pre-meal glucose before each meal to calculate correction doses 1
• 2-hour post-prandial glucose after meals to assess prandial adequacy 1
• Bedtime glucose to evaluate overall daily pattern 1

Long-Term Monitoring

• HbA1c every 3 months during intensive titration 1
• Reassess insulin regimen every 3–6 months once stable 1

Hypoglycemia Management Protocol

Treat any glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate, recheck in 15 minutes, and repeat if needed. 1

• Reduce the implicated insulin dose by 10–20% before the next administration 1
• Never use rapid-acting insulin at bedtime as a sole correction dose—it markedly raises nocturnal hypoglycemia risk 1
• Document every hypoglycemic episode for quality tracking 1

Common Pitfalls to Avoid

• Never delay insulin initiation in patients not achieving glycemic goals with oral medications—prolonged hyperglycemia increases complication risk 1, 2
• Never discontinue metformin when starting insulin unless contraindicated—it reduces total insulin requirements by 20–30% 1, 2
• Never use sliding-scale insulin as monotherapy—major diabetes guidelines condemn this reactive approach 1
• Never continue escalating basal insulin beyond 0.5–1.0 units/kg/day without addressing post-prandial hyperglycemia 1, 2
• Never rely solely on correction doses without adjusting scheduled basal and prandial insulin 1

Expected Clinical Outcomes

• With properly implemented basal-bolus therapy, 68% of patients achieve mean glucose <140 mg/dL versus 38% with sliding-scale alone 1
• HbA1c reductions of 2–3% are achievable over 3–6 months with intensive titration 1
• Correctly executed regimens do not increase hypoglycemia incidence compared with inadequate approaches 1