Insulin Dosage Calculator

Enter your carbohydrate intake, current blood glucose, target blood glucose, and total daily insulin dose (TDID) to calculate your mealtime insulin dose. The calculator splits the result into carb coverage dose and high blood sugar correction dose, giving you a total bolus dose in units. Always confirm dosing with your doctor or diabetes educator before administering insulin.

Disclaimer: This tool is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any health-related decisions.

units/day

The total amount of insulin you take per day (basal + bolus). Your doctor or diabetes educator can provide this value.

grams

Total grams of carbohydrates in the meal you are about to eat.

mg/dL

Your blood glucose level right now, measured with a glucometer.

mg/dL

Your desired blood glucose level after the meal. Typically set by your doctor (often 100–120 mg/dL).

Results

Total Mealtime Insulin Dose

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Carb Coverage Dose

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High Blood Sugar Correction Dose

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Carbohydrate Ratio (500 Rule)

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Insulin Sensitivity Factor (ISF)

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Frequently Asked Questions

What is insulin and why do some people with diabetes need it?

Insulin is a hormone produced by the pancreas that allows cells to absorb glucose from the bloodstream for energy. People with Type 1 diabetes produce little or no insulin, so they must inject it daily. Many people with Type 2 diabetes also require insulin when their body can no longer produce enough or use it effectively.

How do you calculate the mealtime insulin dose?

The mealtime (bolus) dose is calculated in two parts. First, the carbohydrate coverage dose = carb intake ÷ carbohydrate ratio. Second, the correction dose = (current BG − target BG) ÷ insulin sensitivity factor (ISF). Adding these two values gives your total mealtime dose.

What is the carbohydrate ratio and how is it calculated?

The carbohydrate ratio tells you how many grams of carbohydrates one unit of insulin covers. It is estimated using the '500 Rule': divide 500 by your total daily insulin dose (TDID). For example, if your TDID is 40 units, your carb ratio is 500 ÷ 40 = 12.5 g/unit.

What is the insulin sensitivity factor (ISF)?

The insulin sensitivity factor (ISF), also called the correction factor, estimates how many mg/dL one unit of insulin will lower your blood glucose. It is calculated using the '1800 Rule': ISF = 1800 ÷ TDID. If your TDID is 40 units, your ISF = 1800 ÷ 40 = 45 mg/dL per unit.

Do I need to know the carbohydrate content of every meal?

Yes, for accurate carb-based dosing you need to know the grams of carbohydrates in each meal. Food labels, nutrition apps, and resources like the USDA food database can help. Over time, many people with diabetes become skilled at estimating carb counts for common meals.

What is the total daily insulin dose (TDID)?

The TDID is the sum of all insulin units you take in a 24-hour period, including both basal (background) insulin and all bolus (mealtime) doses. It is the foundation for calculating your carbohydrate ratio and ISF. Your doctor or diabetes educator determines this value as part of your personalized care plan.

What type of diabetes requires insulin therapy?

Type 1 diabetes always requires insulin because the pancreas produces none. Type 2 diabetes may require insulin when blood glucose cannot be controlled through diet, exercise, and oral medications alone. Gestational diabetes occasionally requires insulin during pregnancy if lifestyle changes are insufficient.

Is this calculator a substitute for medical advice?

No. This tool is for educational and informational purposes only. Insulin dosing is highly individualized and depends on many factors beyond what this calculator covers. Always consult your doctor, endocrinologist, or certified diabetes educator before adjusting your insulin regimen.