I'm sorry about your gecko. It sounds like he's had a good life with a caring responsible owner.
Many people wonder how to go about putting reptiles down, as it's much more difficult to find veins, etc. About two months ago I had to put one of my snakes down. The vet was able to do this. If you want to know how it is done before deciding feel free to send me a message and I can answer any questions you have (from my experience with this). I do recommend it if you have a vet knowledgeable with exotics that you trust. It's all about the quality of life for your pet and letting them go as peacefully as possible.
added: Please don't freeze your gecko! That is not humane and, as someone else pointed out, does not work the same way with reptiles as other types of animals.
You seem to be a serious animal lover. Not many people would look up humane ways to kill lizards. Dead is dead, but consider this: If I was doomed from the day I was born to have more bad days than good, I wouldn't want to be put out of my misery. If I was doomed at age 30 to have pain every day for the rest of my life, I wouldn't want to be put out of my misery. Now animals may think differently than humans on such subjects, but if they are so different then might they not care about being put down humanely?
Since that is not technically an answer to your question, if I were trying to kill a lizard quickly, I would take a machete or a large knife and sever it's head cleanly. It would twitch for a while, but no pain would be registered.
freezing him is a very good way to put him out of his misery. its way less stressfull too. im so sorry you are dealing with this. I have geckos too and hope that day stays far away x
Awww I'm so sorry to hear this :( the only advice I can give you is to take him to the vet, it's better than letting him suffer. :(
I've heard some say that they can feel their tissue freezing as they die. Don't know if it is true but if it is then freezing it would not be humane. CO2 doesn't work on reptiles either because the way they metabolize. Not sure of a good way but this probably isn't the best place to ask. Call your local vet or humane society
im sorry to hear this but my dog had cancer and arthritis and well he was suffering a lot and we have had him since he was a puppy well the right thing to do was to take him to the vet and stop letting him suffer and accepted to give him a shot to put him down. it was not harmful or anything and we did everything we could. the shot is fast so no suffering. but i don't know if they have that for a gecko but u could ask?
nine tears is a good long life for a leopard gecko. the best way to euthanize (put down) reptiles is to put them in a container and put them in the freezer. they (hibernate in cold weather. by putting him in the freezer he will just go to sleep. i have been keeping reptiles for a long, long time, the way I and so many other herpers euthanize reptiles is by putting them in the freezer. better than the animal suffering. hope this helps and your not paying a vet bill
Since they' re cold blooded they' re body temperature changes with the temperature of their environment. They don' t even feel it because it isn' t cold to them, it' s room temperature to. we feel cold because we produce our own body heat; they don' t.