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, clinical research suggests that fat and protein also impact 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.
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.
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.
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.
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.
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.
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 is determined by the FPU count:
| FPU (rounded) | Modeled Duration | Example Meal |
|---|---|---|
| ≤ 1 FPU | 3 hours | Small amount of cheese or nuts |
| 2 FPU | 4 hours | Chicken breast, moderate fat |
| 3 FPU | 5 hours | Fatty cut of meat, eggs with cheese |
| ≥ 4 FPU | 8 hours | Pizza, large fast food meal, steak dinner |
The Warsaw Method — Background
The Warsaw Method was developed by researchers observing that high-fat and high-protein meals often result in hyperglycemia that standard carbohydrate counting misses entirely.
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
Insulin for these nutrients must not be delivered immediately (which could cause hypoglycemia). Instead it's extended over time — matching the delayed glucose rise.
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.
The Adjustment Factor — Personalizing the Output
The optional Bolus Adjustment Factor allows the calculation to be scaled up or down from the theoretical Warsaw result.
If your ICR, digestion, and fat/protein response are all "average" by the Warsaw model's assumptions, a factor of 1.0 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 0.8 reduces the calculated output by 20%. Entering 0.5 gives you half the theoretical dose — a more conservative starting point for those new to fat/protein dosing 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.
Disclaimers & User Responsibility
❌ Not Medical Advice
This calculator 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.
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. Factor |
| 5 | Modeled Duration | ≤1 FPU→3h, 2→4h, 3→5h, ≥4→8h |