What happens when insulin is introduced in the blood stream directly ??
As you know, insulin is needed to regulate your blood glucose, especially as blood glucose levels begin to rise after you eat. When insulin is produced by the pancreas, it is released in small amounts in response to blood glucose levels over the course of several hours. Injecting insulin just under the skin simulates this response most effectively and safely because the insulin works gradually. But when insulin is injected intravenously, the effect is immediate but very short-lived. Instead of the insulin being gradually absorbed into the circulation from tissue, it is immediately available in the bloodstream. This results in abnormally high insulin levels that can cause a rapid drop in blood sugar levels (hypoglycemia). Hope it helps. For more on insulin refer Byju's