Insulin Types Explained: A PTCB Exam Guide

Why Insulin Knowledge Is Critical for the PTCB Exam

Insulin is one of the most complex and commonly tested medication topics on the PTCB certification exam. With multiple types, brand names, onset times, and storage requirements, insulin questions can be challenging. This guide organizes everything you need to know into a clear, study-friendly format.

Rapid-Acting Insulins

Rapid-acting insulins are used at mealtimes to control blood sugar spikes after eating:

Insulin lispro (Humalog): Onset 15 min, peak 1-2 hr, duration 3-5 hr
Insulin aspart (NovoLog): Onset 15 min, peak 1-2 hr, duration 3-5 hr
Insulin glulisine (Apidra): Onset 15 min, peak 1-2 hr, duration 3-5 hr

Memory tip: Rapid-acting insulins are taken 15 minutes before meals or immediately after eating.

Short-Acting Insulin

Regular insulin (Humulin R, Novolin R): Onset 30 min, peak 2-4 hr, duration 6-8 hr

Regular insulin is the only insulin that can be given intravenously. This is a high-yield PTCB fact. It should be taken 30 minutes before meals.

Intermediate-Acting Insulin

NPH insulin (Humulin N, Novolin N): Onset 1-2 hr, peak 4-12 hr, duration 12-18 hr

NPH is the only insulin that appears cloudy. All other insulins should be clear. This visual distinction is frequently tested. NPH must be gently rolled (not shaken) before injection to resuspend the particles.

Long-Acting Insulins

Insulin glargine (Lantus, Basaglar, Toujeo): Onset 1-2 hr, minimal peak, duration up to 24 hr
Insulin detemir (Levemir): Onset 1-2 hr, minimal peak, duration 12-24 hr
Insulin degludec (Tresiba): Onset 1 hr, no peak, duration 42+ hr

Long-acting insulins provide basal coverage and should not be mixed with other insulins. They are typically injected once or twice daily at the same time each day.

Pre-Mixed Insulins

Humulin 70/30: 70% NPH / 30% regular
Humalog Mix 75/25: 75% lispro protamine / 25% lispro
NovoLog Mix 70/30: 70% aspart protamine / 30% aspart

Storage Requirements

Insulin storage is a common PTCB exam topic:

Unopened insulin: Refrigerate at 36-46 degrees F (2-8 degrees C) until expiration date
Opened/in-use insulin: Room temperature for 28 days (varies by product; Toujeo is 56 days, Tresiba is 56 days)
Never freeze insulin
Protect from heat and direct light

PTCB Exam Tips

Key facts: know the onset, peak, and duration for each category; only regular insulin can be given IV; NPH is cloudy, all others are clear; long-acting insulins are not mixed; and opened insulin is good for 28 days at room temperature.

Master insulin at PTCBprep flashcards and take practice exams.