I'm new to self injection, will be doing the first one tonight, and the doc (who is absolutely clueless about trt and many other things) gave me 21 g needles. My mother has 31g insulin needles she no longer needs and was wondering if anybody has ever used something that small to inject with. If not then what size do I need to order? I'm hoping now that I'm self injecting and am going to twice a week injections rather than once every two weeks maybe I can actually see a benefit from the shots. I can't get this idiot doc to understand that E2 is the enemy when on trt.