Insulin Formulas

Basal Insulin Start

When basal insulin is added to non-insulin antihyperglycemic agents consider:

Diabetes Canada Guidelines: 10 units to start (individualized)

Conservative BBIT Guideline (DCC): 0.1 to 0.2 units/kg = units basal insulin
(e.g. approx. half of BBIT's most conservative TDD 0.3-0.5 u/kg, rounded down for ease)

• E.g. 100.0 kg X 0.1 or 0.2 = 10-20 units starting basal dose 100 kg client
• Tip: Take weight in kg and move decimal to the left for the LOWEST starting dose.
  Double that number for the HIGHEST starting dose. 
• Actual needs can be significantly higher, particularly in those who are resistant, however start conservatively.

To Adjust Basal Insulins: See Insulin Adjustment Page

Bolus Insulin Start

Diabetes Canada Guidelines: 2 - 4 units per meal

Conservative BBIT Guidelines (DCC): 0.05 - 0.1 units / kg = units per meal 

• E.g. 100.0 kg X 0.05 or 0.1 = 5 -10 units
• Tip: Take weight in kg and move decimal to the left for the HIGHEST starting bolus dose per meal. Cut this in half for the LOWEST starting bolus dose per meal. 
• When to start bolus: If on > 0.5 units basal insulin per kg and not at target, consider adding bolus soon (consider A1c, age, complexity, etc).
• Actual bolus needs can be significantly higher, particularly in those who are resistant, however start conservatively. 

To Adjust Bolus Insulins: See Insulin Adjustment Page

Basal & Bolus Start 

• Starting TDD = 0.5 - 1.0 units/kg/day
  (0.3 - 0.5 u/kg/day if more sensitive to insulin; 0.5 - 1.0 u/kg/day if more insulin resistant)
  • Daily basal insulin =  50% of TDD 
  • Daily bolus insulin =  50% of TDD  (distributed amongst 3 meals)
  • Or, if mixed insulin (e.g. 30/70) loosely 2/3 of TDD premix at breakfast and 1/3 at supper.
• Tip: If resistant consider this shortcut:
  • half the weight in kg = total daily basal units
  • half the weight in kg = total daily bolus units (distribute over 3 meals)
• Example for 100 kg resistant patient
  • 50 units basal
  • 50 units bolus
    (50 / 3 meals = 16 units per meal but preferable to individualize.
    e.g. if breakfast is small and supper large, then distribute it proportionately)
• To adjust for BBIT patterns (lows,highs,erratic) see Insulin Adjustment page.

Assessing % Basal in BBIT

• Total daily units basal / total daily units all insulin x 100 = % of insulin as basal
  e.g. 45 units basal for the day / 90 units TDD x 100 = 50% of insulin as basal
• For most people, approximately 40-60% of their total daily dose of insulin (TDD) is basal insulin. This split varies for those on partial-closed-loop insulin pumps due to algorithms. For those with low carbohydrate diets, expect a higher % basal.

Insulin Sensitivity Factor (ISF) or Correction Dose 

To create an ISF for RAPID insulin:

• 100/TDD = number of mmol/L 1 unit rapid will lower glucose level.
  E.g. 100/50 units TDD = 2
  1 unit will drop glucose by about 2 mmol/L
• *Note: If the forumula suggests ISF <2, consider ISF of 2 to start (it's safer). Fine tune later. 

To create an ISF for REGULAR insulin:

• 83/TDD = number of mmol/L 1 unit regular insulin will lower glucose level.
  E.g. 83/30 units TDD = about 3.
  1 unit will lower glucose by about 3 mmol/L

To use an ISF:

• (Current Blood Glucose – target) / ISF= units to give to correct high glucose reading
• e.g. If current BG 13 mmol/L , ISF is 2 and target is 7 mmol then:
  13 mmol/L - 7 mmol/L  = 6 / ISF 2 = 3 units for correction 

Related:

• To adjust ISF, see Insulin Adjustment page for short summary or ISF page for longer description with examples. 
• To create and adjust a correction scale, see the related heading on the ISF webpage..

Carb Ratio (formerly termed Insulin to Carb Ratio or ICR)

To create a Carb Ratio:

• Method 1: Divide grams of available carbohydrate eaten for a meal by bolus dose (units) per same meal to determine the carb ratio
  e.g. 70 g available carb eaten / 5 units rapid = 14. So Carb Ratio 14
  Therefore, for every 14 g available carb eaten, 1 unit of bolus insulin is given
  
  
• Method 2: The 500 rule (500/TDD)
  e.g. 500 / Total Daily Dose of insulin of 50 units = 10. So Carb Ratio = 10
  Therefore, for every 10 g available carb eaten, 1 unit of bolus insulin is given
  
  
• For adjusting ICR, visit Adjusting Insulin Page