Short term either DKA (Diabetic Ketoacidosis) or HHNS (Hyperglycaemic Hyperosmolar Non-ketotic Syndrome) both of which will put you in a coma in the ICU, and HHNS is more common in type II and puts DKA’s sugar readings to shame. I’ve seen photos of glucometers from ICU nurses with an error message that just says “HI” as in, this shit so wild the meter can’t read it.
The long term complications are both waaay worse and waaay more likely.
You can’t give glucose (sugar) through a peripheral (arm) IV when somebody’s on IV nutrition because the sugar crystals literally shred smaller veins, and your body not being able to control its own glucose will do the same thing. This is bad because there’s multiple central and far away parts of your body that rely on little veins.
First of all your internal organs rely on capillaries to bring blood to their individual units, no matter what those cells are doing. Kidneys are a common thing to fail, because those tiny capillaries are what feeds each one of their tiny little filter units.
Your kidneys will also see a lot of the sugar because when your sugar goes up your body will panic and start trying to dump it out in your pee. (That’s why uncontrolled diabetic pee looks syrupy, btw, and you might start getting bladder infections now that your pee could put southern us sweet tea to shame). Once your kidneys start failing it will start messing with your blood pressure in addition to the sugar crystals shredding your veins and all of your arteries and veins will start losing elasticity. This makes them more likely to both clog and burst from the pressure, either of which can cause strokes and heart attacks.
Your extremities on the other hand, especially your fingers and toes, rely on those capillaries to bring oxygen, nutrients, and if needed white blood cells to control infections. So the nerves in your fingers and toes will start dying and you’re lucky if they just go numb. Sometimes the nerves just decide that if they can’t feel a signal from a part they should just tell you it hurts all the time. That’s called neuropathy.
The other thing that will happen is your extremities won’t be able to heal wounds, and not only can they not fight off infections (the white cells can’t get through the shredded veins), but now your blood is also sugary and delicious to both bacteria and fungi. You’ll also be too numb/always in pain to even notice if you get a paper cut, stub or cut your toe, or even just get a sore from new shoes. So if you’re not constantly inspecting your toes for tiny cuts, by the time you even notice an injury it’ll be huge and infected. Gangrene and amputations are extremely common in uncontrolled diabetes. I’ve met numerous diabetics with bilateral above-the knee amputations because it got that far before they realized.
By the way, you’ll start having to pay for a podiatrist, like, a licensed medical doctor, just to cut your toenails. They’ll have to inspect every new pair of shoes you buy too since a sore on your heel can threaten your life now.
Even if you’re constantly inspecting your feet, eventually the blood supply will be so bad that the cells in your fingers and toes won’t be able to keep up and you just get sores anyway, and they’ll almost definitely get infected as described above.
Also, to cap this all off, you’re also gonna go blind. Those glucose molecules are also going to shred your retinas. Diabetes, being high blood sugar, affects everywhere the blood goes.
And because your body is constantly inflamed by both the infections and being shredded every day, you’ll be at extremely high risk for multiple inflammatory processes, particularly strokes. When my psych unit was briefly used for COVID-psych, I had a diabetic stroke out with 0 warning (oh also don’t catch COVID with uncontrolled diabetes that’s one of the biggest risk factors for it killing you or, more likely, permanently disabling you. I’m sure your parents will be much easier to deal with when they’re making fun of your slurred post-stroke speech).