GLP-1 pens have leftover medication: design feature or waste?

What did @dra.gutierrezinternista actually say?

The creator explains that GLP-1 injection pens appear to contain more medication than the prescribed dose, and that this is intentional design, not a bonus dose. She states clearly that the leftover liquid "is not an extra dose" and warns viewers not to use it. She also advises patients to discuss proper injection technique with their doctor to avoid complications like infections or dosing errors.

The core message is straightforward: autoinjector pens for medications like semaglutide and tirzepatide include a small volume of excess liquid, sometimes called overfill or dead volume, built into the device to ensure the intended dose is delivered accurately. She frames this as a safety and precision feature, not a manufacturing error or a windfall of extra medication. She closes by encouraging viewers to consult their physician about proper administration.

Does the science back this up?

Yes, and this is one of those cases where the TikTok content is actually grounded in how these devices work. The overfill in prefilled autoinjector pens is a real, documented design requirement. It is not unique to GLP-1 medications.

Regulatory guidance from bodies including the FDA and the European Medicines Agency requires that injectable drug products contain a small volume in excess of the labeled dose. This overfill accounts for dead volume in the needle hub and plunger, ensuring the stated dose is fully deliverable. For subcutaneous autoinjectors specifically, Rosen et al. (2021, Drug Delivery) described how device dead volume directly affects dose accuracy in biologics and small-molecule injectables, confirming that without overfill, the delivered dose could fall short of the nominal amount.

Novo Nordisk's prescribing information for Ozempic and Wegovy explicitly notes that each pen is designed so that each dose is pre-set and the pen stops automatically. Eli Lilly's documentation for Mounjaro and Zepbound similarly specifies that the pen delivers a fixed dose. The residual liquid visible after injection is intentional, not an error.

What did they get right, and what is missing?

She got the main point right. The overfill is real, the device is engineered for precision, and treating residual medication as an extra dose is genuinely dangerous. That warning deserves credit. Patients have attempted to extract residual liquid from pens and self-administer it, and this creates real risks: inaccurate dosing, injection site contamination, and device misuse.

What is missing, though, is any explanation of why this matters clinically beyond general complications. GLP-1 receptor agonists have a well-characterized dose-response relationship. Even small unintended dose increases can amplify side effects like nausea, vomiting, or gastroparesis symptoms. Davies et al. (2021, Diabetes Care) documented that adverse gastrointestinal events with semaglutide are dose-dependent, meaning unsanctioned dose stacking is not a trivial risk. A 141,000-view video is a real opportunity to explain that, and she stops short of it.

She also does not address compounded GLP-1 formulations, which are administered via vial and syringe rather than a prefilled pen. The overfill concept does not apply in the same way to compounded products, and that distinction matters for a significant portion of the GLP-1 patient population right now.

What should you actually know?

If you are using a brand-name GLP-1 autoinjector pen, the residual liquid after your dose is finished is not yours to use. The pen is engineered so that what comes out during the injection is the dose. What remains is a function of device physics, not pharmaceutical generosity.

Do not attempt to extract leftover liquid from a used pen. The risks include incorrect dosing, contamination, and needle reuse injuries. If you feel your pen did not deliver a full dose, contact your prescriber or pharmacist. Do not attempt to compensate by re-injecting.

If you are using a compounded semaglutide or tirzepatide product drawn from a vial, the dosing mechanics are different and the overfill principle discussed in this video does not directly apply. Your dose accuracy depends on your drawing technique, syringe calibration, and the concentration of your specific compounded formulation. These variables are worth a direct conversation with whoever is managing your prescription.

FormBlends always recommends discussing injection technique, dose questions, and any device concerns with a licensed prescriber before making any changes to how you administer your medication.