Insulin Dosing and Calculations

When may insulin be started initially instead of a GLP-1 agonist in T2DM?

Severe hyperglycemia, symptoms of catabolism, or suspected insulin deficiency

What BG and A1C levels indicate severe hyperglycemia where insulin is started initially in T2DM?

BG ≥300 mg/dL or A1C >10%

If insulin is still required after glucose toxicity resolves in T2DM, what combination is recommended for greater efficacy?

Insulin + GLP-1 agonist

What is the general stepwise approach to starting insulin in T2DM?

Start basal (fasting) insulin first → if fasting glucose is not at goal or A1C is not at goal → add prandial insulin → if the patient is still not at A1C goals → full basal/bolus regimen OR mixed insulin regimen

What determines when insulin doses should be increased in T2DM?

BG and A1C trends

What is the initial basal insulin dose for T2DM? and how is it titrated?

10 units SC once daily OR 0.1–0.2 units/kg/day SC; based on fasting plasma glucose

When should prandial insulin be added to basal insulin in T2DM?

If FPG is at/below goal but A1C remains above goal

What is the initial prandial insulin dose when adding it to basal insulin in T2DM and how should it be taken?

4 units OR 10% of the basal insulin dose SC once daily prior to the largest meal

How is prandial insulin titrated in T2DM?

based on prandial blood glucose, add on doses prior to other meals if needed

What are 2 insulin regimen options if a patient remains above A1C goal after basal and prandial insulin intensification?

Full basal-bolus regimen OR mixed insulin regimen

What does a full basal-bolus regimen consist of for T2DM?

Basal insulin daily + prandial insulin before each meal

What does a twice-daily mixed insulin regimen consist of for T2DM?

NPH + short/rapid-acting insulin, either self-mixed or premixed

Which insulin types are recommended for a physiologic insulin regimen in T1DM and why?

Rapid-acting prandial insulin + long-acting basal insulin;

They provide a physiologic insulin pattern similar to normal endogenous insulin secretion

What is the usual insulin starting dose for a patient with T1DM?

0.4–0.5 units/kg/day using total body weight

How is the TDD generally divided when starting basal-bolus insulin in T1DM?

50% basal + 50% prandial (divided equally among 3 meals)

How to start a basal bolus insulin regimen in T1D

1. calculate TDD (0.4-0.5 u/kg/day)

2. divide TDD into 50% basal and 50% bolus

3. divide the bolus insulin among 3 meals

Can prandial insulin be distributed unequally among meals in T1DM?

Yes; give more for larger meals and less for smaller meals

Why are NPH + regular insulin regimens not preferred?

Their pharmacokinetic profiles do not mimic physiologic pancreatic insulin release as well as long-acting + rapid-acting basal-bolus regimens

What are advantages of an NPH + regular insulin regimen?

Lower cost and fewer injections because the insulins can be mixed

How is the starting TDD calculated for an NPH + regular insulin regimen?

Same TDD calculation as a basal-bolus regimen

(0.4–0.5 units/kg/day using total body weight)

How is the TDD divided in a NPH + regular insulin regimen?

2/3 TDD given in the morning and 1/3 TDD given at night

morning dose is 2/3 NPH and 1/3 regular

evening dose is ½ NPH and ½ regular

What are benefits of insulin pumps?

Excellent BG control and fewer insulin injections

Where is insulin stored in a traditional insulin pump?

In a reservoir

How does insulin travel from a traditional pump into the patient?

Reservoir → tubing → infusion set → cannula → SC tissue

Which insulin pump components require regular replacement?

Insulin reservoir, tubing, and infusion set

Which type of insulin is preferred in insulin pumps?

Rapid-acting insulin

What are the 2 methods by which insulin pumps deliver insulin?

Continuous basal dosing and bolus dosing

How does an insulin pump provide basal insulin?

continuous doses of small amounts of rapid-acting insulin every few minutes

What is the purpose of a bolus dose from an insulin pump and how is the bolus dose calculated?

Cover carbohydrates consumed in a meal;

Using the patient's insulin-to-carbohydrate ratio (ICR)

What is an automated insulin delivery (AID) system and name an example?

A system that integrates CGM data with an insulin pump to automatically adjust insulin doses;

Medtronic MiniMed 780G

How do AID systems respond to changing BG levels?

Detect BG changes in real time and automatically adjust insulin doses

What is the preferred method of insulin delivery when appropriate? When is initiation of an AID system recommended?

Automated insulin delivery (AID); Early initiation is recommended

What is an advantage of an insulin patch pump compared with a traditional pump?

Smaller and more discreet

What is a potential limitation of insulin patch pumps?

Less flexibility with insulin dosing

What type of insulin do patch pumps deliver at mealtimes?

Rapid-acting insulin

How can basal insulin delivery vary among patch pumps?

They may provide continuous basal insulin or no continuous basal insulin, depending on the product

How is an insulin patch pump filled? How is insulin delivered from a patch pump into the body?

Its reservoir is filled with rapid-acting insulin before the patch is applied;

Through a cannula inserted into the skin

How are on-demand doses delivered with a patch pump?

By pressing buttons on the device

Should insulin doses be adjusted based on a single abnormal BG reading?

No; adjustments should generally be based on BG trends

At what times should BG ideally be checked to evaluate insulin trends?

Before breakfast (FPG), lunch, dinner, and at bedtime

Which insulin dose is primarily evaluated when fasting BG is consistently abnormal?

Basal insulin

What should be done when fasting BG trends are

1. low

2. high

1. Decrease the basal insulin dose

2. Increase the basal insulin dose

What are the 2 main approaches to mealtime insulin dosing?

Use the same dose with each meal OR calculate each dose based on carbohydrate intake

When is using the same mealtime insulin dose each day most appropriate?

When carbohydrate intake for that meal is approximately the same each day

What is a disadvantage of using a fixed mealtime insulin dose?

Variable carbohydrate intake can cause high or low BG

When is carbohydrate-based mealtime insulin dosing useful?

When carbohydrate intake varies from day to day

What is the insulin-to-carbohydrate ratio (ICR)?

The grams of carbohydrates covered by 1 unit of insulin

Which rule is used to calculate the ICR for regular insulin?

Rule of 450: ICR = 450 ÷ total daily dose (TDD)

(ICR = g of carbs covered by 1 u of regular insulin)

Which rule is used to calculate the ICR for rapid-acting insulin?

Rule of 500: ICR = 500 ÷ total daily dose (TDD)

(ICR = g of carbs covered by 1 u of regular insulin)

What insulin doses must be included when determining the TDD for an ICR calculation?

Both basal and short- or rapid-acting insulin

How do you calculate a mealtime insulin dose using an ICR?

Grams of carbohydrates in the meal ÷ ICR

What is a correction dose of insulin?

A bolus dose used to lower BG that is above the target range

What is the correction factor (insulin sensitivity factor)?

The amount that 1 unit of insulin is expected to lower BG in mg/dL

Which rule calculates the correction factor for regular insulin?

1,500 Rule: Correction factor = 1,500 ÷ TDD

Which rule calculates the correction factor for rapid-acting insulin?

1,800 Rule: Correction factor = 1,800 ÷ TDD

What insulin doses are included in TDD when calculating a correction factor?

Both basal and short- or rapid-acting insulin

What is the formula for calculating a correction dose for elevated blood glucose?

(Current BG − target BG) ÷ correction factor

Which types of insulin is the correction dose formula for?

both rapid and regular insulin

How are most insulin conversions performed?

1:1 using the same dose

How do you convert twice-daily NPH to once-daily insulin glargine?

Use 80% of the total daily NPH dose

How do you convert Toujeo to another insulin glargine?

Use 80% of the Toujeo dose

Why is the dose reduced when converting twice-daily NPH to glargine?

To reduce the risk of hypoglycemia

Does an insulin conversion dose sometimes require further adjustment?

Yes; adjust based on BG control, such as increasing the dose for hyperglycemia