Why is having too much insulin in the body so bad?

I get that not having enough insulin is bad because the glucose that the tissues need cannot enter the cells to do its job. However, I don't understand why having TOO MUCH insulin is so bad. Surely the more insulin there is the more efficient the glucose is as it can then penetrate the cells that need it. Why... show more I get that not having enough insulin is bad because the glucose that the tissues need cannot enter the cells to do its job. However, I don't understand why having TOO MUCH insulin is so bad. Surely the more insulin there is the more efficient the glucose is as it can then penetrate the cells that need it. Why would having none/very little more glucose left in the extracellular space be so bad if it's not actually getting used anyway?
Update: edit: I mean the hypoglycaemia that results in taking too much insulin...don't understand how it happens
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