We’ve had some such cases in Finland, here’s one example.
She was not. She obtained the insulin from the stock kept on the floor on which she worked, I don’t know with the ativan. This was back about ten years ago. That particular hospital was phasing in an automated dispensing system (Pyxis) but it had some issues and they were only using it for narcotics; she was also a charge nurse and had override codes for the system. Also, typically, hospitals see a lot of patients who are only on insulin for their admissions and go back to oral meds when they go home, and leave the half-empty vials at the hospital. There’s always, or was, extra insulin vials floating around the med carts. I hope things have changed; I haven’t done hospital nursing since around that time.
When I was doing hospital clinicals about 3-4 years ago, about half of the hospitals I worked at considered insulin a “High Alert” drug that required two RN’s to verify the dose before administration and leftovers were strictly tracked. Insulin wasn’t allowed to be left at the bedside any more than a vial of morphine would be. I feel like now I finally know why. Yikes.
Band name!
The Travis McGee novel One Fearful Yellow Eye outlines a very elaborate (possible) murder of a woman by her doctor-husband. In short, she ate her usual sugar-loaded Sunday breakfast, then shot up with what may have been pure water, and died in a snowbound house while he was out on a call. The empty insulin vial tested at full strength… but had the doctor switched them? (It’s not 100% resolved.)
Humulin insulin is available OTC too; it’s done this way so diabetics don’t have to jump through any hoops to get it. Ativan would have come from the dispensing machine, and if she’d pocketed a few partial vials, she could have come up with enough to put her to sleep without raising any suspicions. 
I almost did this once. Dialed up my usual 60-unit dosage for Lantus on the Humalog pen, had the needle screwed on and everything. Only at the last second before I actually injected did it break through my brainfog (I was just really tired, not drunk) that I was holding the blue pen instead of the grey one. The proximity of a moment of probably fatal stupidity was not comfortable…
In fact, endogenous glucagon release is just one way the body attempts to counter the effects of low sugar. Another important defence is through the release of adrenalin (aka epinephrine). Either one alone, glucagon or adrenalin, is sufficient to overcome most hypoglycaemic episodes. However, when a huge quantity of insulin has been injected, even that dual system is overwhelmed. Insulin not only lowers the blood sugar directly, but it also inhibits precisely those metabolic processes which are essential for producing sugar and thus reversing hypoglycemia (in other words, during extreme insulin excess, the body’s ability to manufacture new glucose, or release stored glucose, is shut down).
Interestingly, but teleologically making sense, is the fact that insulin also inhibits glucagon release. So, during a massive insulin overdose, the only mechanism operating in the short term to produce glucose and reverse the hypoglycemic state, is adrenalin release and action.
And, just to be complete, although it is definitely the case that cortisol (and growth hormone) are also released by the body during hypoglycemia, they take hours to work and are thus useless in reversing the acute, life-threatening hypoglycemia of an insulin reaction (or deliberate overdose).