Insulin Dosage
Calculate your mealtime insulin dose based on carbohydrate content, blood glucose levels, and total daily insulin. Free insulin dosage calculator with carb ratio and correction.
About This Calculator
What is the Insulin Dosage Calculator?
The Insulin Dosage Calculator helps people with diabetes calculate their mealtime (bolus) insulin dose using the carbohydrate counting method and blood glucose correction. It uses the 500-rule to determine your carbohydrate ratio and the 1800-rule to calculate your insulin sensitivity factor, giving you a precise insulin dose for any meal.
This calculator is designed for individuals on intensive insulin therapy who need to adjust their mealtime insulin based on what they eat and their current blood glucose level. It computes two components: carbohydrate coverage (how much insulin you need for the carbs in your meal) and high blood sugar correction (additional insulin to bring elevated glucose down to target).
How It Works
The carbohydrate ratio is calculated as 500 divided by your total daily insulin dose (TDID). This tells you how many grams of carbohydrates one unit of insulin covers. For example, with a TDID of 50 units, your carb ratio is 10 g per unit. The insulin sensitivity factor (ISF) is calculated as 1800 divided by TDID, telling you how many mg/dL one unit reduces your blood glucose. Your carb coverage dose is your meal carbs divided by the carb ratio, and your correction dose is your current BG minus target BG divided by ISF.
Regional Application
India: Blood glucose is typically measured in mg/dL. The 500 and 1800 rules apply universally. Indian diabetic associations recommend consulting your endocrinologist for personalized insulin-to-carb ratios.
United States: The American Diabetes Association recommends the carbohydrate counting method. The 500/1800 rules are widely used as starting points for insulin dose calculation. Pre-meal target glucose is typically 80-130 mg/dL.
United Kingdom: The NHS supports carbohydrate counting for insulin dose adjustment. Blood glucose targets may vary — the Diabetes UK recommends individualised targets. Always follow your diabetes care team's guidance.
Frequently Asked Questions
How do I calculate my mealtime insulin dose?
Your mealtime insulin dose is calculated in two steps: first, divide your meal carbohydrate content by your carbohydrate ratio (500 divided by total daily insulin dose) to get the carb coverage dose. Second, divide the difference between your current and target blood glucose by your insulin sensitivity factor (1800 divided by total daily insulin dose) to get the correction dose. Add both for your total mealtime dose.
What is the carbohydrate ratio for insulin?
The carbohydrate ratio tells you how many grams of carbohydrates are covered by one unit of insulin. It is calculated by dividing 500 by your total daily insulin dose (TDID). For example, if your TDID is 50 units, your carb ratio is 500/50 = 10 grams per unit. Typical values range from 1 unit per 10 to 15 grams of carbohydrates.
What is the insulin sensitivity factor?
The insulin sensitivity factor (ISF) tells you how many mg/dL one unit of insulin will lower your blood glucose. It is calculated by dividing 1800 by your total daily insulin dose (TDID). For example, if your TDID is 50 units, the ISF is 1800/50 = 36 mg/dL per unit. Typical values range from 30 to 50 mg/dL per unit.
When should I use insulin for high blood sugar correction?
High blood sugar correction insulin is used when your pre-meal blood glucose is above your target level. The calculator subtracts your target from your current reading and divides by your insulin sensitivity factor. If your current blood glucose is below your target, no correction dose is needed — taking insulin would risk hypoglycemia.
Is this calculator suitable for type 1 and type 2 diabetes?
This calculator is designed for anyone using intensive insulin therapy, which includes many people with type 1 diabetes and some with type 2 diabetes. The 500-rule for carbohydrate ratio and 1800-rule for insulin sensitivity factor are starting points. Your doctor may prescribe different ratios based on your individual needs and insulin sensitivity.
How do I determine my total daily insulin dose (TDID)?
Your total daily insulin dose (TDID) is the sum of all insulin you take in a day, including both basal (long-acting) and bolus (mealtime) insulin. It should be prescribed by your doctor. A rough estimate is 0.5 to 1.0 units per kilogram of body weight, but individual needs vary based on insulin resistance, activity level, and other factors.
What if my calculated dose seems too high or too low?
If your calculated dose seems unusual, first double-check your inputs — especially the total daily insulin dose and carbohydrate count. Never adjust your insulin regimen without consulting your healthcare provider. Factors like illness, stress, exercise, and changes in diet can all affect your insulin needs.
What are the risks of incorrect insulin dosing?
Taking too much insulin can cause hypoglycemia (low blood sugar), leading to symptoms like dizziness, confusion, sweating, and loss of consciousness. Taking too little insulin can cause hyperglycemia (high blood sugar), which over time can lead to serious complications including nerve damage, kidney disease, and cardiovascular problems. Always consult your healthcare provider.