Humalog Dose Calculator
Calculate your exact Humalog (insulin lispro) dose for meals and high blood sugar correction using your carb ratio and sensitivity factor.
🍽️ Humalog Dose Calculator
ICR = grams of carbs covered by 1 unit. Don't know yours? Use our Carb Ratio Calculator (500 ÷ TDD).
+ Add pre-meal correction dose (optional)
Don't know yours? Calculate ISF (1800 ÷ TDD)
Estimated Humalog Dose
Total estimated bolus (carb dose + correction if entered)
(carbs ÷ ICR)
(if BG entered)
How to Use This Calculator
Count Your Carbs
Total the grams of carbohydrate in your planned meal. Use food labels, a carb counting app, or a dietitian's guidance.
Enter Your ICR
Input your insulin-to-carb ratio. If you don't know it, our Carb Ratio Calculator estimates it from TDD using the 500 Rule.
Add Correction (Optional)
If your pre-meal BG is above target, expand the correction section. Enter current BG, target BG, and your ISF.
Calculate
Your carb bolus, correction bolus (if entered), and combined total are displayed with the full formula.
Check Insulin on Board
Before dosing any correction, subtract active insulin from recent doses (IOB). This calculator does not model IOB.
Confirm With Your Team
Your actual ICR is set by your care team through real-world testing — use this estimate as a discussion tool, not a prescription.
How Humalog Insulin Dosing Works
Humalog insulin — also called prandial or bolus insulin — is the rapid-acting dose taken before or at meals to handle the blood glucose rise from carbohydrates eaten. It is one part of a full bolus: some people also add a correction component if their pre-meal reading is above target.
Carb Bolus Formula
Example: 75g carbs ÷ ICR of 12 = 6.25 → rounded to 6.5 units. ICR is your insulin-to-carb ratio: the number of grams one unit covers. Source: Walsh et al., J Diabetes Sci Technol. 2011.
Optional Correction Added to Meal Bolus
If pre-meal BG = 180 mg/dL, target = 100, ISF = 40: correction = (180 − 100) ÷ 40 = 2 units. Total bolus = carb dose + 2. Important: subtract any insulin on board (IOB) before adding a correction.
What Is ICR and Where Does It Come From?
ICR is estimated using the 500 Rule: divide 500 by your total daily dose. If TDD = 40, ICR ≈ 12.5g/unit. This is a starting estimate — your real ICR is verified by checking your blood glucose 2 hours after meals and adjusting. An ICR that's too aggressive (too low) causes post-meal hypoglycemia; one that's too lenient (too high) causes persistent post-meal hyperglycemia. Many people also have different ICRs at different meals due to time-of-day insulin resistance variations (e.g., more resistant in the morning).
This calculator does not account for fat and protein in meals. High-fat meals slow carbohydrate absorption, potentially causing late glucose spikes hours after eating. Some people with Type 1 use extended or dual-wave boluses for such meals — discuss this with your diabetes educator.
Sources & References
- Walsh J, Roberts R, Bailey T. "Guidelines for Optimal Bolus Calculator Settings in Adults." J Diabetes Sci Technol. 2011;5(1):129–135.
- American Diabetes Association. Standards of Medical Care in Diabetes — 2024. Section 9. Link
- Hirsch IB. "Insulin Analogues." N Engl J Med. 2005;352:174–183.
Last reviewed: June 2025
Frequently Asked Questions
How do I calculate my Humalog dose?
Humalog bolus = grams of carbohydrates ÷ insulin-to-carb ratio (ICR). If your ICR is 1:10 and you eat 60g carbs, bolus = 60 ÷ 10 = 6 units. If your pre-meal BG is above target, add a correction: (current BG − target BG) ÷ ISF. Subtract any insulin on board (IOB) from the correction before dosing. Always confirm your ICR with your diabetes care team.
What is insulin-to-carb ratio?
ICR is the number of grams of carbohydrate covered by one unit of rapid-acting insulin. A ratio of 1:10 means one unit covers 10g carbs. ICR is estimated by the 500 Rule (500 ÷ TDD) as a starting point, then refined through real-world testing. ICR often differs by meal time — many people need a lower ratio (more insulin) at breakfast due to morning insulin resistance from cortisol and growth hormone peaks.
Should I add a correction dose to my Humalog bolus?
If your pre-meal BG is above your target, adding a correction to the carb bolus is common practice. Total bolus = carb bolus + correction. However, you must subtract insulin on board (IOB) from any correction first to avoid stacking doses. This calculator adds the correction to the carb bolus but does not model IOB — your pump or CGM system may track IOB automatically. Discuss stacking precautions with your care team.
How many carbs does one unit of insulin cover?
The 500 Rule estimates this: 500 ÷ TDD. If TDD = 50 units, one unit covers approximately 10g of carbs. This ranges widely — from 5–6g per unit for people with high insulin requirements to 20+ grams per unit for those who are very insulin-sensitive. Your actual ratio is determined through careful monitoring with your diabetes care team, not by formula alone.
Does fat and protein affect mealtime insulin dose?
Yes, significantly. High-fat meals slow gastric emptying and carbohydrate absorption, causing delayed glucose spikes 2–5 hours after eating. High-protein meals can also raise blood glucose, especially in Type 1 diabetes, due to gluconeogenesis. Standard carb-counting bolus calculators do not account for fat or protein. Many people with Type 1 on pumps use extended boluses (dual-wave or square-wave) for high-fat meals like pizza. Your diabetes educator can advise on strategies.