We don't recommend pre-filling syringes.....what we usually suggest if there's a caretaker giving shots is to fill a "sample" syringe with a colored liquid so the person giving the shots has something to compare to
This was my experience as well.I recently pre-filled prozinc. The recommendation was to roll bottle before pre-filling, & then roll syringe before injecting. Also, stored with cap up to prevent clogging. Can you ask your vet? (This is my experience.)
The lubricant may degrade the insulin.The research I've seen for Lantus is that there are concerns about the lubricant in the syringes causing issues with the effectiveness of the insulin. With Lantus pre-filling is not recommended.