You can raise your own insulin level by eating carbohydrates, preferably about an hour after you work out, which can push more protein into your muscles. Giving yourself a shot of insulin, however, can be extremely dangerous.
A case was reported in the German medical journal Anasthesiologie Intensivmedzin, Notfallmedizin, Schmerztherapie that involved a 30-year-old man who was an active bodybuilder (33:461-463;1998). His blood sugar dropped to dangerous hypoglycemic levels instantly, and he was taken to a hospital where he ‘lost consciousness and showed signs of convulsions.’ He was infused with glucose and required having a tube inserted down his throat to allow respiration. He was in the intensive care unit and was lucky to survive. The bodybuilder took the insulin as preparation for an international competition to try and stimulate muscle growth, with dire results.
Do not use insulin unless you are diabetic. Trying to use it as an anabolic agent can be deadly.