You can use an insulin syringe to withdraw insulin from the Lantus pen. Sounds to me like you are using the pen (like a small, long vial of insulin) with pen needles. With those pen needles, you can only change doses in 1 unit increments. You also have to prime the pen each time you give insulin (the instructions call it giving an 'air shot' after you attach the needle) and you waste 2 units each time with the needed priming of the pen cartridge.
If you use an insulin syringe instead of the pen needles, you can change doses in 0.25 Units.
Go buy U100 insulin syringes at any drugstore and go to the pharmacy section. Look for U100 1/3 cc syringes with half unit markings. These hold a total of 30 units. Walmart sometimes carry them, but many of the pharmacy techs don't know it so have them double check behind the counter.
Your profile says you live in Oklahoma and insulin syringes are available over the counter. Individual pharmacies may have a policy against selling syringes (to cut down on illegal drug use). Call around and ask. You may need a prescription from your vet. Oklahoma City restricts sales of syringes, do know if you live there, so that is why I suggested getting a prescription for the syringes from a vet.
There was a cat over in the Prozinc forum that recently had a hypo (hypoglycemia from too much insulin), an insulin overdose. Ended up at the vet for 3 days at around $1000 a day.
Here is her post about that hypo. Click on the blue highlighted text and it will take you directly to that post
. Talks about some of the symptoms.
Scary to have this happen to your cat
