1. Core Concepts & Goals
Objective: To ensure the correct dose of medication is delivered to the correct injection site using proper technique to achieve optimal health outcomes.
Golden Rule: Insulin and GLP-1 receptor agonists should be injected into the subcutaneous tissue (fat), avoiding intramuscular (IM) injection.
Primary Complication: Lipohypertrophy (rubbery lesions) is the most common complication and leads to glycemic variability and unexplained hypoglycemia.
2. Device Selection & Needle Length
Pen Needles vs. Syringes
Needle Length Standard: 4-mm pen needles are suitable for all patients regardless of BMI (Body Mass Index).
They reduce the risk of intramuscular (IM) injection compared to longer needles.
They provide equivalent glycemic control to 8-mm or 12-mm needles even in patients with obesity.
Syringes: The shortest available syringe needle is currently 6-mm.
Not Recommended: 12-mm or 12.7-mm needles are generally not recommended due to high IM risk.
Safety & Hygiene
Single Use Only: Needles and syringes should be used once and disposed of immediately.
Consequences of Reuse: Needle breakage, clogging, inaccurate dosing, and lipohypertrophy.
Disposal: Use approved sharps containers; never resheathe (recap) needles.
3. Injection Technique
Preparation
Hand Washing: Always wash hands with soap and water; disinfect injection site if required (e.g., hospital setting) but let alcohol dry completely.
Cloudy Insulin (NPH/Premix): Gently roll 10 times and tip 10 times until milky white. Do not shake.
Priming: Always prime the pen (air shot) to ensure flow. Note: GLP-1 pens may only need priming once per first use (check manufacturer).
Insertion & Angle
4-mm Needles: Inject at a 90-degree angle. A skin lift (pinch-up) is generally not required for adults but may be needed for very lean limbs/abdomens.
6-mm Syringes/Needles:
90-degree into a skin lift.
45-degree may be required for lean individuals if no skin lift is used.
8-mm Needles: Must use a skin lift and inject at 90 degrees. Lean patients should use a 45-degree angle with a skin lift.
The “Skin Lift” (Pinch-up)
Method: Lift skin and subcutaneous tissue delicately between thumb and index finger.
Avoid: Do not lift muscle. Do not squeeze so hard it causes blanching or pain.
Dwell Time
Count to 10: After the dose knob is fully depressed, hold the needle in place for a slow count of 10 seconds to ensure full dose delivery and prevent leakage.
4. Injection Sites & Rotation
Site Selection
Preferred Site: The abdomen is preferred for consistent absorption, especially for soluble (Regular) and NPH insulin.
Other Sites: Thighs (upper third anterior lateral) and Buttocks (posterior lateral upper).
The Arm: The arm is not a preferred site for self-injection due to difficulty ensuring a 90-degree angle and high risk of IM injection into the deltoid.
Avoid: Umbilicus (stay 2-3 cm away), moles, scars, and lipohypertrophy.
Rotation Strategy
Systematic Rotation: Essential to prevent lipohypertrophy.
Spacing: Injections should be spaced at least 1 to 2 cm (one finger width) apart.
Plan: Rotate sites within the same anatomical area (e.g., abdomen) at the same time of day to reduce glycemic variability.
5. Complications: Lipohypertrophy
Definition: “Rubbery” or thickened lesions in the fat tissue caused by insulin’s anabolic effect and needle reuse/lack of rotation.
Consequences:
erratic/blunted absorption (insulin pooling).
Unexplained hypoglycemia or hyperglycemia.
Increased insulin requirements (higher doses needed).
Detection: Visual inspection and palpation (sweeping motion with fingertips).
Management: Stop injecting into the area immediately. Use a new needle every time. Rotate sites.
Clinical Pearl: When switching from a lipo (rubbery) site to healthy tissue, reduce the insulin dose (often by ~20%) to prevent hypoglycemia, as absorption will suddenly improve.
6. Special Populations
Pregnancy
Preferred Site: Abdomen.
Third Trimester: Use the lateral sides of the abdomen (flanks) as the central skin becomes taut.
Needle: Use 4-mm needles to avoid fetal harm or IM injection.
Pediatrics
Needles: 4-mm is the safest length.
Technique:
Children >6 years: 4-mm at 90 degrees (no pinch usually needed).
Children 2-6 years: 4-mm with a skin lift.
Sites: Buttocks may be better for preschool children due to more fat tissue.
Older Adults
Considerations: Thinner skin, reduced dexterity, cognitive changes.
Device: Pens are preferred over syringes for safety and ease of use.
Cognitive Assessment: Use the Clock Drawing Test to assess ability to manage injection therapy.
7. Insulin Infusion (Pumps)
Change Frequency: Infusion sets should be changed every 2 to 3 days to prevent infection and lipohypertrophy.
Cannula Selection:
Teflon: Flexible, comfortable. Change every 2-3 days.
Steel: For those with Teflon allergies or kinking issues (e.g., pregnancy, high muscle mass). Change every 2 days.
Troubleshooting: “Unexplained hyperglycemia” = Check for occlusion/kinking. If ketones present, give insulin via pen/syringe immediately.
8. Storage & Handling
In-Use Insulin: Store at room temperature (max 25-30°C) to reduce injection pain and air bubbles.
Usually good for ~28 days (check manufacturer).
Unopened Insulin: Refrigerator (2 to 8°C). Do not freeze.
Extreme Temps: Avoid direct sunlight or temperatures >30°C.