Total Daily Dose (TDD) Insulin Calculator
Calculate total daily insulin dose from body weight, or enter a known TDD to instantly derive your carb ratio and sensitivity factor. Educational use only.
📊 TDD Calculator
Results
Estimated Total Daily Dose
units/day
units/day
g carbs per unit
mg/dL per unit
How to Use This Calculator
Choose Your Mode
"From Weight" calculates TDD using the standard formula. "Enter Known TDD" accepts your real daily dose and skips straight to derived values.
Enter Weight or TDD
For weight mode, select your diabetes type — this determines the dose factor. For known TDD, just enter the number.
Select Insulin Type
Rapid-acting analogs use the 1800 Rule for ISF; Regular (human) insulin uses the 1500 Rule.
Review Derived Values
See TDD, basal/bolus split, insulin-to-carb ratio, and sensitivity factor — all computed from your TDD in one step.
Verify the Formula
Every result shows the exact calculation. Share it with your provider to discuss how your actual values compare.
Titrate With Your Team
Use the estimate as a starting point — your actual TDD is refined through weeks of titration against real blood glucose data.
What Is Total Daily Dose and Why Does It Matter?
Total daily dose (TDD) is the single most important number in insulin management. It represents the total insulin your body uses in 24 hours — basal plus all bolus doses combined — and it is the foundation for every other insulin calculation. Get TDD right, and the derived ratios (carb ratio, sensitivity factor) become accurate starting points. Use a wrong TDD and every downstream calculation is off.
TDD from Weight
Standard ADA starting range. This calculator uses 0.5 u/kg as the Type 1 midpoint and 0.2 u/kg as the conservative Type 2 insulin-naïve start. Worked example: 80 kg × 0.5 = 40 units/day.
Empirical TDD (If Already on Insulin)
If you already take insulin, adding up your actual doses over a representative week gives a more accurate TDD than any formula. Use the "Enter Known TDD" mode above to feed this into the carb ratio and ISF calculations.
Derived Values from TDD
Once TDD is known, carb ratio and sensitivity factor follow directly. A TDD of 40 gives ICR = 12.5 g/unit and ISF = 45 mg/dL/unit (rapid-acting).
Basal–Bolus Split
TDD is typically divided roughly 50/50 between basal and bolus insulin as a starting point. In practice, the split is adjusted based on whether fasting or postprandial glucose is the primary problem. Some people do better at 40/60 or 60/40; your provider will guide the right split for your pattern.
Sources & References
- American Diabetes Association. Standards of Medical Care in Diabetes — 2024. Link
- Walsh J, Roberts R, Bailey T. "Guidelines for Optimal Bolus Calculator Settings." J Diabetes Sci Technol. 2011;5(1):129–135.
- Davidson PC et al. "Analysis of guidelines for basal-bolus insulin dosing." Endocr Pract. 2008;14(9):1095–1101.
Last reviewed: June 2025
Frequently Asked Questions
What is total daily dose of insulin?
TDD is the total insulin units used in 24 hours — all basal and bolus doses combined. It is the foundation for calculating insulin-to-carb ratio (500 ÷ TDD) and insulin sensitivity factor (1800 ÷ TDD). A 70 kg adult with Type 1 might have a TDD of ~35 units/day, while someone with significant insulin resistance might use 80+ units/day. TDD is determined by actual usage and clinical titration, not formulas alone.
How do I calculate my total daily insulin dose?
Two methods: (1) Formula estimate: TDD = weight (kg) × 0.5 u/kg/day — a starting point for those new to insulin. (2) Empirical method: If you already inject, add up all units taken over 3–7 representative days and divide by the number of days. The empirical method is more accurate because it reflects your actual insulin requirements, not a population average.
What is a high total daily dose of insulin?
There is no universal threshold — it depends on body weight and insulin resistance. A TDD above 1.0–1.5 u/kg/day may indicate significant resistance. People with obesity and Type 2 diabetes sometimes require 100–200+ units/day. At very high TDD, concentrated insulins (U-200 Humalog, U-300 Toujeo, U-500 Regular) reduce injection volume and are prescribed under specialist supervision. This calculator shows a plausibility warning for TDD above 500 u/day.
How is TDD used to calculate carb ratio and ISF?
Carb ratio (ICR) = 500 ÷ TDD — gives grams of carbohydrate covered by 1 unit of rapid-acting insulin. Insulin sensitivity factor (ISF) = 1800 ÷ TDD for rapid-acting analogs — gives mg/dL blood glucose drop per unit. Both are starting estimates. Real-world ICR and ISF need verification: check 2-hour postprandial readings (for ICR) and correction dose response (for ISF) with your care team.
Should I use calculated or actual TDD in this tool?
If you already take insulin regularly, your actual empirical TDD (average over several days) will produce more accurate ICR and ISF estimates than the weight-based formula. The weight formula is best for people just starting insulin who don't yet have usage data. Use the "Enter Known TDD" mode in the calculator above if you know your real daily total.