My first two TRT injections were in the docs office with an 1.5" 18ga needle. I've seen lawn darts that looked smaller and the first one left a bruise in my quad for more than a month. I could have qualified for a handicap permit after the 2nd one.

I've since been self administering at home with a 23ga needle and haven't had any problems. Minimal injection site soreness and you can definitely inject slowly enough with a small needle to minimize the pain. Injecting slowly is the best advice I've read about pinning.