Insulin pens are widely adopted devices for managing diabetes, allowing users to dial and inject a specific dose of medication. Before each injection, a necessary preparation step called “priming” ensures the pen is ready to deliver the correct amount. Priming involves expelling a small quantity of insulin into the air to confirm functionality and maintain the accuracy of the delivery.
Defining Insulin Pen Priming
Priming is the mechanical action of forcing a small amount of insulin out of the pen’s needle tip just before an injection. This process clears the needle assembly of any trapped air. Since a user attaches a new, sterile needle for each injection, the small space within the needle hub is filled with air upon attachment. Priming replaces this air with liquid insulin, ensuring the delivery system is functional and ready for the intended dose. Successful completion is confirmed visually by seeing a drop or stream of insulin appear at the needle tip. The routine need for priming is directly tied to attaching a new needle for every dose, verifying both the pen’s flow and the needle’s patency.
Why Priming is Required Before Every Injection
Priming is required before every injection, especially when a new needle is attached, because skipping this step compromises dose accuracy. The empty space inside the new needle hub is filled with air. If priming is skipped, this air is injected first, displacing the equivalent volume of insulin intended for delivery.
This presence of air leads to under-dosing, which is a serious concern for blood sugar control. If the air bubble occupies the space of one or two units, the patient receives less insulin than dialed for, potentially resulting in hyperglycemia over time.
Air bubbles can also accumulate within the insulin cartridge itself during normal use or due to temperature fluctuations. Priming consolidates these air pockets and forces them out through the needle. This ensures the plunger mechanism pushes only liquid insulin, not a mixture of air and insulin.
Another function of priming is verifying the patency of the needle and the mechanical integrity of the pen. The expelled drop confirms that the needle is not blocked, bent, or clogged with dried insulin. If no drop appears, it signals a blockage or a problem with the pen’s internal mechanism, guaranteeing the intended dose will be delivered completely.
Step-by-Step Guide for Accurate Priming
Preparing the Pen and Setting the Dose
The priming process begins with securing a new, sterile needle onto the pen mechanism immediately before the injection. After removing the protective caps, the user sets the dose dial to the required priming units. While two units is the standard recommendation for most pens, consulting the manufacturer’s instructions is advised, as some devices may require three to five units.
Expelling Air and Confirming Flow
Next, the pen must be held vertically with the needle pointing upward. This orientation allows air bubbles within the cartridge to rise and be expelled first. A gentle tapping of the cartridge area can help dislodge any bubbles clinging to the sides.
The user then presses the injection button fully until the dose counter returns to zero. This action dispenses the small priming dose, and a visible drop or thin stream of insulin should appear at the needle tip. Continue holding the button down for a few seconds to ensure the full volume is dispensed. Once the drop is confirmed, the pen is ready for the therapeutic dose.
Identifying and Addressing Priming Failures
A priming failure occurs when the user dials the test dose and presses the injection button, but no drop of insulin appears at the needle tip. The most common cause is a blocked or damaged needle, often due to a bent tip or dried insulin clogging the opening.
If no drop appears on the first attempt, the initial corrective action is to repeat the priming process. Dial up another two units and press the injection button again while holding the pen upright. If insulin still fails to appear after this second attempt, the entire needle must be removed and replaced with a new, sterile one. A new needle often resolves the issue immediately by eliminating the blockage.
If the pen consistently fails to prime even after attaching a new needle, the problem may be related to the pen’s internal mechanics or a large air lock within the cartridge. In this situation, the pen should not be used for the scheduled injection, as the correct dose cannot be guaranteed. Check the insulin’s expiration date, ensure the pen is not damaged, and contact a healthcare professional or the manufacturer for troubleshooting.