I also reused syringes for a week or more and lancets for month for the 25 years I did shots. Have used a pump the last decade, but I still reuse needles on the occasions I inject a large dose now and for the 6 -8 times a day I test. I don’t use rubbing alcohol or prep my skin in any way and have never had any type of infection. The risk of injection is tiny if you’re in good health. The modern syringes manufactured in recent years are thinner and can’t be reused as long, but I see little health benefit from using a new one each time.
The polyethylene construction of these disposable syringes usually makes them rather chemically resistant. There is, however, a risk of the contents of the syringes leaching plasticizers from the syringe material. Non-disposable glass syringes may be preferred where this is a problem. Glass syringes may also be preferred where a very high degree of precision is important (. quantitative chemical analysis ), because their engineering tolerances are lower and the plungers move more smoothly. In these applications, the transfer of pathogens is usually not an issue.