Section 01
Overview — What This Estimator Does
This Fat-Protein Bolus Estimator is a digital tool designed to help individuals visualize the theoretical impact of dietary fat and protein on insulin dosing, based on the principles of the Warsaw Method.
While traditional insulin dosing relies primarily on carbohydrate counting, published research shows that fat and protein can also affect blood glucose levels — potentially causing delayed or sustained increases that can catch people off guard hours after a meal. This estimator converts those macronutrients into a standardized metric that makes that effect easier to reason about.
This tool is educational only. It does not provide medical advice or diagnosis. Always consult your healthcare provider before adjusting insulin dosages. The outputs are theoretical estimates, not prescriptions.
Section 02
How the Calculation Works
The estimator runs four sequential steps. You can see every step in detail by clicking "Show Calculation Steps" in the results panel above.
Convert Macronutrients to Calories
Fat and protein are converted to their caloric values using standard nutritional constants.
Protein calories = Protein (g) × 4 kcal/g
Fat calories = Fat (g) × 9 kcal/g
Total = Protein cal + Fat cal
Example: 30g protein (120 kcal) + 20g fat (180 kcal) = 300 kcal total
Fat calories = Fat (g) × 9 kcal/g
Total = Protein cal + Fat cal
Example: 30g protein (120 kcal) + 20g fat (180 kcal) = 300 kcal total
Calculate Fat-Protein Units (FPUs)
Per the Warsaw Method, 100 kcal derived from fat and/or protein equals 1 Fat-Protein Unit (FPU). This provides a standardized, unit-based way to talk about non-carbohydrate glucose impact.
FPU = Total kcal ÷ 100
Example: 300 kcal ÷ 100 = 3.0 FPU
Example: 300 kcal ÷ 100 = 3.0 FPU
Think of one FPU as roughly equivalent in glucose-raising effect to 10 grams of carbohydrates — but spread out over hours rather than peaking quickly. Loads under 1 FPU (under 100 kcal) are not counted.
Calculate Carbohydrate Equivalent
The Warsaw Method equates 1 FPU to approximately 10 grams of carbohydrates. This allows the fat/protein load to be expressed in familiar carb-equivalent terms that can be divided by ICR.
Carb Equivalent = FPU × 10g
Example: 3.0 FPU × 10 = 30g carbohydrate equivalent
Example: 3.0 FPU × 10 = 30g carbohydrate equivalent
Calculate Theoretical Insulin Equivalent
The carbohydrate equivalent is divided by the user's Insulin-to-Carb Ratio (ICR) to estimate the theoretical additional units of insulin. If an Adjustment Factor is applied, the result is scaled accordingly.
Theoretical Insulin = (Carb Equivalent ÷ ICR) × (Adjustment % ÷ 100)
Example: (30g ÷ 10 ICR) × 1.0 = 3.0 units theoretical
Example: (30g ÷ 10 ICR) × 1.0 = 3.0 units theoretical
Modeled Duration
The Warsaw Method recommends delivering this additional insulin as an extended (square wave) bolus — spread over time to match the slow, delayed glucose rise from fat and protein digestion. The duration comes from the FPU count, using the table published by the Warsaw group. It is the same table the Bolus 4 estimator uses. Loads under 1 FPU aren’t counted at all, and fractions aren’t rounded up — 2.7 FPU is treated as 2:
| FPU | Modeled Duration | Example Meal |
|---|---|---|
| Under 1 FPU | Not counted | A little cheese or a handful of nuts |
| 1.0 – 1.9 FPU | 3 hours | Eggs with a slice of cheese |
| 2.0 – 2.9 FPU | 4 hours | Chicken breast, moderate fat |
| 3.0 – 3.9 FPU | 5 hours | Fatty cut of meat, eggs with cheese and bacon |
| 4 FPU and up | 8 hours | Pizza, large fast food meal, steak dinner |
Section 03
The Warsaw Method — Background
The Warsaw Method comes from Ewa Pańkowska and colleagues at the Medical University of Warsaw (Pediatric Diabetes, 2009). It is built on the observation that high-fat and high-protein meals often cause late high blood sugar that carb counting alone misses.
Later studies found the full Warsaw amount caused lows for some people. That is why reduced factors are often discussed, and why this page includes an adjustment percentage.
A The Core Problem
Dietary fat slows gastric emptying, meaning glucose from carbs (and from fat/protein conversion) enters the bloodstream more slowly — and over a much longer time window than expected.
B The FPU Standard
By converting non-carb calories into Fat-Protein Units, the method provides a standardized metric for estimating the additional dosing needs that carb counting alone won't capture.
C Extended Delivery
The Warsaw approach spreads this insulin over time rather than giving it all at once, to match the slower glucose rise from fat and protein.
D Individual Variation
The Warsaw Method is a generalized formula. Digestion speed, gastroparesis, hormonal changes, and other individual factors can all affect accuracy for any given person.
Important context: The Warsaw Method is a clinical reference framework. It was not designed to be applied mechanically without individualization and professional oversight. The FPU-to-insulin conversion is a starting point for a conversation with your care team — not an exact prescription.
Section 04
The Adjustment Percentage — Personalizing the Output
The optional Bolus Adjustment (%) scales the math up or down from the Warsaw result. It works the same way as the adjustment in the Bolus 4 estimator.
If your ICR, digestion, and fat/protein response are all "average" by the Warsaw model's assumptions, 100% applies the formula as written. But most people aren't average, and the standard calculation can be too aggressive or too conservative for any given individual.
Entering 80 scales the math down by 20%; 50 scales it to half. The factor only shows how the numbers move. Any starting point is a decision to make with your care team.
This setting should only be adjusted in consultation with your diabetes management team. Incorrectly stacking insulin for fat and protein on top of a carbohydrate bolus carries real risk of hypoglycemia. Always monitor carefully when experimenting with new strategies.
Continuous Glucose Monitor (CGM) data is especially valuable here — it gives you the real-time feedback to see whether the modeled duration and dose are matching your actual glucose response.
Section 05
Disclaimers & User Responsibility
❌ Not Medical Advice
This estimator is an educational utility. It does not replace the clinical judgment of a healthcare professional. Do not use this tool to determine medication dosages without prior training and approval from your diabetes management team.
⚠️ Individual Variation
The Warsaw Method is a generalized formula. Individual metabolic responses to fat and protein vary significantly. Factors including digestion speed, gastroparesis, and hormonal changes can render these calculations inaccurate for some individuals.
⚠️ Risk of Hypoglycemia & Hyperglycemia
Incorrect use of extended boluses, or stacking insulin for fat and protein on top of carbohydrate boluses, carries a risk of severe low or high blood sugar. Monitor carefully and work with your care team.
📊 Continuous Monitoring
It is strongly recommended to use a Continuous Glucose Monitor (CGM) or perform frequent finger-stick testing when experimenting with new dosing strategies, in order to safely monitor the body's response over time.
Bottom line: This tool estimates a theoretical number based on math. It does not know your body, your current blood glucose, your active insulin, your activity level, or any of the dozens of other variables that affect actual insulin needs. Use it to learn and have better conversations with your care team — not as a standalone dosing guide.
Quick Reference
The Full Calculation at a Glance
| Step | What It Calculates | Formula |
|---|---|---|
| 1 | Total Calories | (Protein × 4) + (Fat × 9) |
| 2 | Fat-Protein Units (FPU) | Total kcal ÷ 100 |
| 3 | Carbohydrate Equivalent | FPU × 10g |
| 4 | Theoretical Insulin | (Carb Equiv ÷ ICR) × Adj.% |
| 5 | Modeled Duration | <1→none, 1→3h, 2→4h, 3→5h, 4+→8h |
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