Can Total Daily Dose (TDD) of insulin be calculated daily based on basal, bolus, and correction doses to adjust new basal and bolus dosing for hospitalized patients with impaired glucose control?

Daily TDD Recalculation for Inpatient Insulin Adjustment: Not Recommended

You should NOT calculate TDD daily based on basal + bolus + correction doses to adjust insulin for hospitalized patients. This approach fundamentally misunderstands how insulin therapy should be managed in the hospital setting and can lead to dangerous dosing errors.

Why Daily TDD Recalculation Is Inappropriate

Basal Insulin Should Be Adjusted Based on Fasting Glucose, Not Total Daily Use

• Basal insulin titration must be based on fasting plasma glucose values, not on the total amount of insulin administered the previous day 1, 2.
• The American Diabetes Association recommends increasing basal insulin by 2 units every 3 days if fasting glucose is 140-179 mg/dL, or by 4 units every 3 days if fasting glucose is ≥180 mg/dL 2, 3.
• Basal insulin addresses fasting and between-meal glucose levels through restraining hepatic glucose production—it does not address postprandial hyperglycemia 2.

Correction Insulin Reflects Acute Hyperglycemia, Not Basal Needs

• Correction (sliding scale) insulin addresses acute hyperglycemic excursions and does not accumulate to steady state 2.
• If you recalculate TDD daily including correction doses, you will inappropriately escalate basal insulin in response to postprandial hyperglycemia, leading to "overbasalization" 2, 4.
• The two components (basal and correctional insulin) should be adjusted independently on their respective schedules 2.

The 3-Day Titration Standard Exists for Safety Reasons

• Basal insulin can be adjusted every 3 days after a change is made, even when patients are concurrently receiving short-acting insulin (SSI) three times daily 2.
• This 3-day interval allows sufficient time to assess the effect of dose changes while avoiding dangerous over-correction 2, 3.
• Do not wait longer than 3 days between basal insulin adjustments in stable patients, as this unnecessarily prolongs the time to achieve glycemic targets 2.

The Correct Approach to Inpatient Insulin Management

Scheduled Basal-Bolus Regimen Is Preferred

• Outside of critical care units, scheduled subcutaneous insulin that delivers basal, nutritional, and correction components (basal-bolus regimen) is recommended for patients with good nutritional intake 1.
• Sole use of sliding scale insulin in the inpatient hospital setting is strongly discouraged 1.

Initial Dosing for Hospitalized Patients

• For hospitalized patients who are insulin-naive or on low-dose insulin, the American Diabetes Association recommends a total daily dose of 0.3-0.5 units/kg, with half as basal insulin 2, 3.
• For patients on high-dose home insulin (≥0.6 units/kg/day), reduce the total daily dose by 20% to prevent hypoglycemia 2, 3.
• Lower doses (0.1-0.25 units/kg/day) are recommended for high-risk patients, such as the elderly (>65 years), those with renal failure, or poor oral intake 2, 3.

Basal Insulin Titration Protocol

• Titrate basal insulin based on fasting glucose values every 3 days 2, 3:
  • If fasting glucose ≥180 mg/dL: increase by 4 units
  • If fasting glucose 140-179 mg/dL: increase by 2 units
  • Target fasting glucose: 80-130 mg/dL
• If hypoglycemia occurs without clear cause, reduce the dose by 10-20% immediately 2, 3.

Prandial Insulin Adjustment

• Prandial insulin should be titrated by 1-2 units or 10-15% every 3 days based on pre-meal and 2-hour postprandial glucose readings 2, 3.
• Start with 4 units of rapid-acting insulin before the largest meal or 10% of the current basal dose 2, 3.

Correction Insulin Guidelines

• Correction insulin should be adjusted based on insulin sensitivity factor (ISF), calculated as 1500/TDD or 1700/TDD 2.
• If correction doses consistently fail to bring glucose into target range, adjust the ISF, not the basal dose 2.

Critical Threshold: Recognizing Overbasalization

Warning Signs That You're Escalating Basal Insulin Inappropriately

• When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, consider adding prandial insulin rather than continuing to escalate basal insulin alone 1, 2, 4.
• Clinical signals of overbasalization include 2, 4:
  • Basal insulin dose >0.5 units/kg/day
  • Bedtime-to-morning glucose differential ≥50 mg/dL
  • Hypoglycemia
  • High glucose variability

What to Do Instead of Increasing Basal Insulin

• Add prandial insulin when fasting glucose is at target but A1C remains above goal after 3-6 months of basal insulin titration 4.
• Add prandial insulin when significant postprandial glucose excursions occur (>180 mg/dL) 4.

When TDD Should Be Recalculated

Periodic Reassessment, Not Daily Recalculation

• Total daily dose (TDD) should be recalculated periodically (every few weeks to months) to update carbohydrate-to-insulin ratios and correction factors, not daily 2.
• For type 1 diabetes on pump therapy, approximately 40-60% of TDD should be basal delivery, with the remainder as mealtime and correction boluses 2.
• For multiple daily injections with long-acting analogs, generally 50% of TDD should be given as basal insulin 2.

Common Pitfalls to Avoid

The Danger of Daily TDD Recalculation

• Continuing to increase basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia leads to suboptimal control and increased hypoglycemia risk 2, 4.
• Blood glucose in the 200s mg/dL likely reflects both inadequate basal coverage AND postprandial excursions requiring mealtime insulin 2.

Hypoglycemia Management Failures

• 75% of hospitalized patients who experienced hypoglycemia had no basal insulin dose adjustment before the next administration 1, 2.
• A hypoglycemia management protocol should be adopted and implemented by each hospital or hospital system 1.
• For individual patients, treatment regimens should be reviewed and changed as necessary to prevent further hypoglycemia when a blood glucose value of <70 mg/dL (3.9 mmol/L) is documented 1.

Monitoring Requirements

• In hospitalized patients with diabetes who are eating, bedside glucose monitoring should be performed before meals; in those not eating, glucose monitoring is advised every 4-6 hours 1.
• Assess adequacy of insulin dose at every clinical visit, looking for signs of overbasalization, and adjust the basal dose by 10-20% immediately if hypoglycemia occurs 2.