I work in LTC and always use alcohol to clean the skin before all injections whether it be to check glucose levels or inject insulin. I believe there is EBP to confirm infection control issues. I do also realize there is question as to whether any alcohol residue may alter BS values. I dry the alcohol with a few swift hand waves before puncturing the skin and if the pt. has enough blood I wipe the first drop away and use the second. Also, I always wipe the top the insulin bottle before puncturing it as well.
At home, my husband does this all without alcohol but as mentioned before the only 'bugs' at home are our own and the environment is more controlled as far as infection is concerned.
I say wipe everything at work, it may take a bit longer but in the end it is about pt. safety and quality care.