Insulin Administration and Dosing Management for Diabetes

Insulin Dosing Principles

Insulin dosing is not "one size fits all"; it is a highly individualized process often calculated based on a patient's body weight.

The Total Daily Dose (TDD)

A common starting point for calculating the Total Daily Dose (TDD) is: $0.3\text{--}0.5\text{ mg/kg/day}$

This TDD is typically divided into a 50/50 ratio between basal and bolus insulin:

1. Basal Insulin: Provides a steady, background level of insulin to manage glucose during fasting and between meals.
2. Bolus Insulin: Administered at mealtimes to manage carbohydrate intake and lifestyle habits.

Clinical Tip: The Rule of 500 To estimate how many grams of carbohydrates are covered by a single unit of insulin, clinicians use the "Rule of 500": $\text{Grams of Carbohydrates per 1 unit} = \frac{500}{\text{TDD}}$

Classification of Insulin Types

Insulins are categorized by their onset, peak, and duration of action.

1. Basal Insulins (Long and Intermediate Acting)

Basal insulin mimics the steady endogenous insulin production of the pancreas.

• Ultra Long-Acting: These are dosed once weekly. An example is Insulin Icodec. When switching to Icodec, a loading dose is required (daily dose $\times$ 10.5) for the first dose only.
• Long-Acting: Dosed once daily.
  • Insulin Detemir: Has a shorter duration of action among the long-acting types and may show diminishing effects toward the end of the dosing interval.
  • Insulin Glargine: Provides coverage over 24 hours. Higher concentrations, such as Toujeo ($300\text{ u/mL}$), offer a longer duration of action than standard $100\text{ u/mL}$ concentrations.
• Intermediate-Acting: NPH insulin is dosed twice daily (BID). It is characterized by a cloudy appearance and a peak effect at 5–8 hours.

2. Bolus Insulins (Rapid and Short Acting)

Bolus insulins are used to manage post-prandial (after meal) glucose spikes.

• Ultra Rapid-Acting: Such as Insulin Aspart (e.g., NovoRapid) or the even faster Fiasp.
• Rapid-Acting: Such as Insulin Glulisine (Apidra) or Insulin Lispro (Humalog).
• Short-Acting: Regular Insulin (e.g., Humulin R) has a slower onset (approx. 30 mins) compared to analogues.

Clinical Complications and Management

Lipohypertrophy

Because insulin is an anabolic hormone, improper administration can lead to lipohypertrophy—the buildup of fatty tissue at injection sites. To prevent this, patients must practice regular rotation of injection sites and use appropriate needle lengths.

Hypoglycemia (Low Blood Sugar)

Hypoglycemia is the most immediate clinical concern. Blood sugar levels under $4\text{ mmol/L}$ can cause symptoms, and levels below $3\text{ mmol/L}$ are considered severe.

Management Protocol:

1. If conscious: Follow the "Test-Treat" rule. Consume $15\text{g}$ of fast-acting carbohydrates, wait 15 minutes, and re-test.
2. If unconscious/severe: Call 911 and administer Glucagon (via IM injection or intranasal spray like Baqsimi).