Bolus Insulin Calculator: Meal and Correction Dose
See how a mealtime insulin dose is worked out from the carbs you eat, your insulin-to-carb ratio, your current reading, your target and your correction factor. For education only: always follow the plan your care team gave you. Nothing you enter is stored.
Your data is not stored or sent to the server. All calculations are performed locally in your browser.
- It uses general rules of thumb. Your own ratios and correction factor should come from your diabetes care team and can differ a lot from these estimates.
- It is for education and for discussing settings with your team. Do not use it to change your insulin doses on your own.
- A wrong insulin dose can cause dangerous low or high blood sugar. If you feel unwell, follow your care plan or get medical help.
Worked example
60 g of carbs, ratio 1:10, glucose 200 mg/dL, target 120 mg/dL, correction factor 40 mg/dL per unit, no insulin on board.
| Step | Working | Units |
|---|---|---|
| Meal dose | 60 ÷ 10 | 6.0 |
| Correction dose | (200 − 120) ÷ 40 | 2.0 |
| Total | 6.0 + 2.0 | 8.0 |
How it's calculated
Meal dose = carbohydrate (g) ÷ insulin-to-carb ratioCorrection dose = (current glucose − target) ÷ correction factorTotal = meal dose + correction dose − insulin on board (applied to a positive correction only)Sources: Nationwide Children's Hospital: Calculating bolus injections; Walsh et al., J Diabetes Sci Technol 2011; ADA: Hypoglycemia symptoms and treatment
Last reviewed
Frequently asked questions
How is a mealtime bolus worked out?
It has two parts. The meal dose is the grams of carbohydrate divided by your insulin-to-carb ratio. The correction dose is your current glucose minus your target, divided by your correction factor. The two are added together.
What is insulin on board?
Insulin on board is insulin from earlier doses that is still working. Counting it avoids 'stacking' doses. This calculator only uses it to reduce the correction part, never the meal dose, because the earlier insulin was already meant to bring a high down.
What happens if I'm below my target?
The correction becomes negative and reduces the meal dose. If your reading is below 70 mg/dL (3.9 mmol/L) the calculator shows no dose at all: treat the low first.
How do I treat a low?
The ADA's 15-15 rule: have 15 g of fast-acting carbohydrate, wait 15 minutes and recheck. If you are still below 70 mg/dL, have another 15 g. Young children usually need less; follow your care plan.
Why is the result not a whole number?
The maths gives an exact figure, but most pens and syringes dose in half or whole units. How to round, up or down, is something to agree with your care team.
Where do my ratio and correction factor come from?
From your diabetes care team, ideally. The insulin-to-carb ratio and correction factor calculators on this site show common rules of thumb for starting estimates.
Related calculators
All diabetes tools- Insulin-to-Carb Ratio CalculatorEstimate how many grams of carbohydrate one unit of insulin covers with the 500 or 450 rule.
- Insulin Sensitivity Factor CalculatorEstimate how far one unit of insulin lowers your blood sugar with the 1800 or 1500 rule, in mg/dL and mmol/L.
- Blood Sugar ConverterConvert blood glucose between mg/dL and mmol/L and see where a reading sits against standard ranges.