This article is for general education and is not medical advice. Priming steps vary by pen model — always follow the specific instructions that came with your device.
It's a small step that's easy to rush past or skip entirely once a routine sets in — but priming your pen before an injection matters more than it might seem. Here's what it actually does.
What is priming?
Priming — sometimes called a "safety test" or "air shot" — is the step where you dial a small amount (often 2 units or a manufacturer-specified amount) and press the injection button while the pen is pointed upward, before attaching it to your skin. A small stream or drop of medication should appear at the needle tip. This confirms the needle isn't blocked and that air has been cleared from the connection between the needle and the medication cartridge.
Why it matters: the air problem
Every time a new needle is attached, a tiny amount of air can be trapped in the needle hub or at the connection point. If that air isn't cleared before injecting:
- Part of your dose could be delivered as air instead of medication, meaning you might receive less than the intended amount.
- A blocked or bent needle tip might not be caught until you're already trying to inject the real dose.
Priming addresses both: it clears trapped air and confirms the needle path is actually open before the dose that counts.
When priming is needed
This varies by device, so your pen's specific instructions are the authority, but general patterns include:
- Every time you attach a new needle — this is the most consistent rule across pen types, since a fresh needle attachment is exactly when air can get trapped.
- The first time you use a brand-new pen, even before the first needle attachment in some cases, to clear air from a fresh cartridge.
- Some devices specify priming before every single dose, not just with a new needle — check your pen's leaflet, since this differs by manufacturer and model.
How to prime: general steps
- Attach a new needle and remove both the outer and inner needle caps.
- Dial the priming dose your pen's instructions specify (commonly a small fixed amount).
- Hold the pen with the needle pointing straight up.
- Press and hold the injection button fully.
- Watch for a small stream or drop of medication at the needle tip.
- If nothing appears, repeat the process (up to the number of times your instructions allow) before assuming a problem with the pen or needle.
Once you see the drop, you're ready to dial your actual dose and proceed with the injection — see our full step-by-step injection guide for what comes next.
What if no drop appears after repeated attempts?
This usually points to one of a few things:
- The needle isn't fully attached — check that it's screwed or clicked on securely.
- The needle itself may be faulty or blocked — try a fresh needle from the box before troubleshooting further.
- The pen cartridge may be empty or nearly empty — check the dose window or remaining-medication indicator.
If a fresh needle and confirming the cartridge still doesn't resolve it, contact your pharmacist rather than proceeding with a dose you're not confident was delivered correctly.
Common priming mistakes
- Skipping it entirely once the routine feels familiar — the risk of trapped air doesn't go away just because you're experienced.
- Not holding the pen upright during priming, which can prevent air from properly clearing.
- Confusing the priming dose with your actual medication dose — always redial to your real prescribed dose after priming, since the priming amount is separate.
- Assuming a new pen doesn't need priming the very first time it's used, when many devices specifically require it.
Does priming waste medication?
The small amount used for priming is factored into how pens are designed and dosed overall — it's an expected and necessary part of using the device accurately, not an avoidable waste. Skipping it to "save" medication risks a much bigger problem: an inaccurate actual dose.
Frequently asked questions
Do I need to prime every single time I inject, or just with a new needle?
This depends on your specific pen model — some require priming with every new needle attachment, others with every dose. Check your device's instructions rather than assuming.
What happens if I forget to prime and inject anyway?
You may receive less than your full intended dose if air was trapped in the needle. If you realize immediately, contact your pharmacist or provider about how to handle that specific dose — don't simply redose without guidance.
Why do I need to point the pen upward to prime?
Air rises to the top of the cartridge when the pen is held with the needle up, which is what allows the priming step to push that air out through the needle rather than medication.
Is priming the same as checking for air bubbles like with a syringe?
It serves a similar purpose — clearing air before the real dose — but the mechanism is different since pens don't involve drawing medication up visually the way syringes do.
Can a new needle ever come pre-blocked from the manufacturer?
It's uncommon but possible, which is part of why priming exists — it catches a blocked or faulty needle before you rely on it for your actual dose.
Educational content only — not medical advice. Always follow your specific pen manufacturer's priming instructions. Last reviewed: August 2026.