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Before we start learn some basics;

TDD – total daily dose of insulin (all basal and boluses)

Basal –background insulin pumped slowly through out the day to keep blood glucose level flat.

Bolus – a quick surge of insulin as Carb boluses to cover carbs Correction boluses to lower high readings that arise from too little basal insulin delivery or insufficient carb boluses.

Bolus On Board (BOB) – the units of bolus insulin or glucose-lowering activity still working from recent boluses.

Duration of Insulin Action (DIA) – time that a bolus will lower the BG. This is used to calculate BOB.

Difference Between Basal and Bolus Insulin?

Basal insulin controls blood glucose throughout the day and night. On the other hand, bolus insulin controls blood glucose after eating.

Therefore, this is the key difference between basal and bolus insulin. Moreover, basal insulin is slow acting and long-lasting. In contrast, bolus insulin is short-acting or mealtime insulin.

Furthermore, basal insulin is effective for 24 hours, while bolus insulin is effective for 2-4 hours. So, this is also a significant difference between basal and bolus insulin.

Insulin Dosage Calculator - - Find Here

This insulin dosage calculator was created to show you how to calculate insulin dose with as little effort as possible. Your insulin dose regimen should be prescribed by your doctor, however, may still need to determine your mealtime insulin dose. To do this, you will need to know the carbohydrate content of your meal, your current and target blood glucose, the carbohydrate ratio, and the insulin sensitivity factor. The last two can be easily calculated once the total daily insulin dose is known.

How to calculate the Total Daily Dose (TDD) of Insulin?

For patients undergoing an intensive insulin therapy, their insulin dose regimen is partially prescribed by the doctor, but there are still some calculations that need to be made before establishing the dose of insulin. This insulin dosage calculator provides formulas that allow you to calculate how much bolus insulin you should take for your meal. It helps you to account for the carbohydrate content of your meal, and to correct for high blood sugar concentrations.

To do this, you need to know the following information:

-The carbohydrate content of your meal.

-The carbohydrate ratio, which tells you how many grams of carbohydrates are covered by one unit of insulin.

-Current blood glucose concentration.

-Target blood glucose concentration.

-The insulin sensitivity factor, which tells you by how many points (mg/dL) one unit of insulin will decrease your blood glucose.

The two elements above that are not in bold can be calculated using your total daily insulin dose. When you know all the necessary information, your mealtime insulin dose can be calculated in three easy steps:

Step one - Carbohydrate Coverage

Carb. Content / Carb. Ratio = Carb. Coverage insulin dose
Step two - High Blood Sugar Correction

(Current BG - target BG) / ISF = high blood sugar correction insulin dose
Step three - Total Mealtime Insulin Dose

Carb. Coverage insulin dose + high blood sugar correction insulin dose = total mealtime dose
Abbreviations: carb.is carbohydrate, BG. is blood glucose, ISF is insulin sensitivity factor

Please note, that this calculator will not work if your current blood glucose is below your target blood glucose.

For example:160lb divided by 4 = 40 units OR 72.7kg x 0.55 = 40 units Then for basal bolus calculate what percentage you want. Typically, 40% basal and 60% bolus. Ex) 40% of 40 units = 16 u basal & 60% of 40 units = 24u bolus total then divide by 3= 8units per meal (for 3 meals per day)

How to Calculate Insulin Sensitivity Factor (AKA Correction Factor)?

The insulin sensitivity factor tells you how many points (mg/dL) one unit of insulin will decrease your blood glucose by. It can be determined by your doctor or calculated when total daily insulin dose is known.

1800 / TDID = insulin sensitivity factor
1800 is the constant used for the initial calculation of insulin sensitivity factor
TDID is total daily insulin dose

For example:

  • 1800 / 50 units = 36 mg/dL, which means that one unit of insulin decreases blood glucose by 36 mg/Dl
  • 1500 divided by Total Daily Dose of insulin (TDD) if patient uses rapid acting insulin OR 1800 divided by TDD if patient uses regular insulin Ex) TDD = 40 units so 1500/40 = 37.5 If current premeal BG is 160 and the target BG is 90 you would take the current BG subtract the target BG then multiply by the correction factor. Ex) (160-90)/37.5 = 1.9 units
  • Usually, the values for the insulin sensitivity factor range from 30 to 50 mg/dL.

How to Calculate Carbohydrates to Insulin Ratio?

If you suspect that your carb ratio is off (often running high or low after meals could be a good indicator of that), it’s time to collect data in the form of blood sugar readings and do some analysis.

If you want good results, you need good data, and you’re the only one who can collect it. As with most other things related to diabetes, it requires work, but it’s worth it.

We suggest following the 4 steps below for 3-5 days minimum to collect data for you or your doctor to assess whether your carb ratio is correct. If you and/or your doctor don’t see any trends after 3-5 days, you’ll have to collect more blood sugar data.

1. Focus on one meal at a time (breakfast, for example). Try to enjoy the meal at roughly the same time each day and eat the same foods and quantities for the data collection period (this is why breakfast is a good place to start, as it is easier to eat the same thing for breakfast each day)

2. Make sure your carb count is correct and stick with the same carb ratio for the data collection period.

3. Try not to do anything that impacts your blood sugar significantly right before or after the meal (like going for a run).

4. Be on top of your blood sugar measurements or Continuous Glucose Monitor (CGM).

  • I. Measure your blood sugar before the meal
  • II. Measure your blood sugar after the meal (90-120 minutes after your injection)

After 3-5 days, you should have enough data to start assessing whether your carb ratio for this time of day is accurate.


When you or your doctor does the analysis, you’ll focus on whether your blood sugar was in your desired range before the meal and whether your blood sugar came back into your desired range within 90-120 minutes of your insulin injection. Carbohydrate coverage the bolus dose for food coverage is prescribed as an insulin to carbohydrate ratio. The insulin to carbohydrate ratio represents how many grams of carbohydrate are covered or disposed of by 1 unit of insulin.

This is the number of grams of carbohydrates that is covered by 1 unit of insulin. How to calculate: 500 divided by TDD Ex) 500/40 = 12.5 grams per unit (I:C ratio is 1:12.5) So if 90-gram meal then you would divide 90 by 12.5 = 7.2 units If target BG is above range for 2-3 days, then decrease C:I ratio by 10-20%, if target BG is below range for 2-3 days then increase C:I ratio by 10-20%.

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