Overview — What This Companion Covers
This page is a companion to Juicebox Podcast Episode 820, "The Math Behind Setting Basal Insulin." It walks through the weight-based formulas commonly referenced in diabetes education for establishing a theoretical Total Daily Dose (TDD) of insulin, and from that, an estimated basal range.
These calculations appear in standard diabetes textbooks and are used by clinicians as a starting point — not a finished prescription. The formulas are population averages. Your actual insulin needs will depend on a wide range of individual factors that no formula can fully capture.
The TDD Formula — Where It Starts
For adults who are not in the honeymoon phase, the basic Total Daily Dose estimate begins with body weight. There are several equivalent ways to express the same formula:
Weight (lbs) × 0.25 = TDD estimate
Weight (kg) × 0.55 = TDD estimate
Example: 150 lbs ÷ 4 = 37.5 units estimated TDD
To convert: lbs ÷ 2.2 = kg (or lbs × 0.454 = kg)
This gives an estimated total of all insulin per day — both basal (background) and bolus (mealtime) combined. From that number, the expected basal dose is typically 40–60% of TDD.
Basal High = TDD × 0.60
Example: 37.5u TDD → Basal range: 15u – 22.5u per day
The Davidson/Bode research provides a related formula that includes a slightly different constant and a correction factor calculation:
Basal = 0.47 × TDD
Correction Factor (CF) = 1700 ÷ TDD
Carb-to-Insulin Ratio (CIR) = 2.8 × weight (lbs) ÷ TDD
Source: Davidson & Bode — pubmed.ncbi.nlm.nih.gov/19158048
Age Groups — The Formulas Differ
The standard adult formula does not apply uniformly across all ages. Insulin sensitivity and resistance change significantly through childhood, adolescence, and older adulthood.
| Age Group | TDD Starting Point | Basal Range (u/kg) | Notes |
|---|---|---|---|
| Adult (standard) | Weight (lbs) ÷ 4or kg × 0.55 |
0.15 – 0.70 u/kg | Covers inactive to very active adults not in honeymoon phase |
| Child (pre-puberty) | Weight (lbs) × 0.20or kg × 0.44 |
0.15 – 0.60 u/kg | Lower starting TDD than adults; activity adjustment still applies |
| Adolescent | Similar to adult TDD | 0.25 – 1.0 u/kg basal alone | Wide range due to puberty-driven insulin resistance; can be significantly higher than adult needs |
| Older Adult | Lower than standard adult | 0.1 – 0.5 u/kg | Basal needs tend to decrease with age; more conservative starting point |
⚠️ Adolescent Insulin Resistance
Puberty introduces significant hormonal changes that can drive insulin resistance well beyond adult levels. The adolescent basal range of 0.25–1.0 u/kg is intentionally wide — some teenagers require dramatically more insulin than the standard weight-based adult formula would suggest. This is a physiological reality, not a dosing error.
🧒 Pre-Puberty Starting Point
Children prior to puberty typically need less insulin than adults relative to body weight. The multiplier of 0.20 (lbs) or 0.44 (kg) provides a lower starting TDD. Activity level adjustments apply here just as they do for adults — a very active child will be toward the lower end of the basal range.
Activity Level — How It Shifts the Range
For all age groups, Total Daily Dose and basal needs typically decrease the more active the person is. Initial assessment is usually done at a moderate activity level, with adjustments made up or down based on real-world data.
| Activity Level | Basal Range (u/kg/day) | Context |
|---|---|---|
| Very Active | ~0.15 u/kg | High-intensity daily exercise, athletics |
| Active | ~0.25–0.35 u/kg | Regular exercise, physically demanding lifestyle |
| Moderate | ~0.40–0.50 u/kg | Standard starting point for most assessments |
| Low Active | ~0.55–0.60 u/kg | Mostly sedentary with light occasional activity |
| Sedentary | ~0.65–0.70 u/kg | Little to no regular physical activity |
Tools & Referenced Books
OpenSourceDiabetes.org Tool
For a more comprehensive pump settings optimization tool, John Walsh PA and Ruth Roberts MA (co-authors of Pumping Insulin) maintain a free calculator at:
This tool takes your current weight, current insulin doses, current blood glucose, and target blood glucose — then calculates suggested adjustments. It includes a note to contact your provider before acting on any suggestions.
Recommended Books
📘 Think Like a Pancreas
Gary Scheiner, MS, CDCES
Dosing strategy charts, tables, and the math behind insulin management in accessible language.
📗 Pumping Insulin
John Walsh / Ruth Roberts
The reference book for insulin pump settings. Includes the formulas this simulator is based on.
📙 Type 1 Diabetes in Children, Adolescents and Young Adults
Dr. Ragnar Hanas
Comprehensive pediatric and adolescent dosing strategies including age-adjusted formulas.
🔬 Davidson & Bode Research
The AIM system study providing the alternative formula: TDD = 0.24 × weight (lbs).
All Formulas at a Glance
| Group | TDD Formula | Basal Range |
|---|---|---|
| Adult | lbs ÷ 4 or kg × 0.55 | 40–60% of TDD · 0.15–0.70 u/kg |
| Child (pre-puberty) | lbs × 0.20 or kg × 0.44 | 0.15–0.60 u/kg |
| Adolescent | Similar to adult | 0.25–1.0 u/kg basal alone |
| Older Adult | Lower than adult | 0.1–0.5 u/kg |
| Davidson/Bode | lbs × 0.24 | Basal = TDD × 0.47 |
| kg conversion | lbs ÷ 2.2 or lbs × 0.454 | — |