Related, a doctor who reuses syringes.
If you do want to reuse syringes there is an important difference between the two types that are available. Syringes that are kept individually sterile with a plastic cap over each end have an advantage over the ones that use a plastic and paper blister pack.
Once these are taken out of the blister pack, the protective plastic cap over the needle does not form a complete seal around it, at least with the brand I was using. There are 3 contact points between the cap and the barrel of the syringe. Between these contact points there are 3 gaps and one day when I was reaching for a preloaded syringe, I saw a fruit fly crawl out through one of the gaps and fly away.
Note that a gap in the end cap of some syringes has room for the thick end of a toothpick or for some of our wildlife to go through.
They are very small and they seek out moisture, usually in drains when they are in a house. The room didn't have one and the fruit fly had found the tip of my loaded syringe. With that kind of enthusiasm its portion of the fruit fly gene puddle is probably rapidly expanding, so I wouldn't expect this problem to be just a really remote chance that isn't likely to happen ever again.
I used up the box I had of these syringes but I always kept them in a second container. A container for traveler's toothbrushes works well. They are also great for travelling with a loaded syringe. If the finger tabs of the syringe are a bit too wide, they can be trimmed off with nail clippers or scissors.
A lot of studies about reusing syringes have their authors concluding that there is no reason not to reuse syringes, and there is a good reason to do so, to reduce waste and expense. The largest study I've read was:
"A Prospective Study of the Hazards of Multiple Use of Disposable Syringes and Needles in Intensified Insulin Therapy" by R. Chlup, E. Marsalek, and W. Burns. Published in Diabetic Medicine. 7(7):624-7, 1990 Aug.
It covered about 560,000 injections.
"Each syringe was reused for 1 to 12 weeks; each needle for 4 to 200 injections (average 41) within 1 to 40 days (average 11.2). In a total of 560,000 of injections no relevant signs of infection could be found. In rare cases slight redness not exceeding 4 mm square could be seen at the injection sites."
They concluded their summary of the study with:
"Thus, the repeated use of syringes and needles in one diabetic patient may be recommended as a convenient and safe approach in insulin administration."
They covered more than a half million injections, which as they point out would be 5 injections a day for more than 300 years.
Unfortunately most of these studies are not available online, or they are behind a pay wall. (It's a peeve. The studies were funded by public money.) I had to look them up at a medical library.
There is a short abstract of one study on a US government website. It covered 23,664 injections. Here is a quote from it.
"Compliance with standard aseptic precautions was poor, with only 29% of patients following recommended practices. No adverse effect of syringe reuse was identified. The authors conclude that diabetic patients frequently reuse disposable syringes, without apparent harmful effect." Source: http://www.ncbi.nlm.nih.gov/pubmed/
The rate of infections with reused syringes might not be zero. It may also be possible to be infected using only new syringes. If you are puncturing the skin there is some risk. The point is that the infection rate does not increase when reusing syringes, not that it is absolute zero.
The infection rate is extremely low and I really like syringes for using insulin. Most of the injections don't hurt at all and on the ones where you do hit a nerve there isn't much pain if you do your injections quickly. I can't imagine a system that would work better as you can be so precise with the amounts of insulin.
A few details that most people would understand but a few might not. Keep the end cap on at all times when the syringe is not in use.
You do not want to share the syringes with another person. The reuse is only for one person.
Some insulins are not meant to be mixed with any other type of insulin. Use a different syringe for Lantus, or for other types requiring it.
Related, a doctor who reuses syringes.