Both my younger brother and I got diagnosed with Type 2 diabetes. I was diagnosed 19 years ago. I modified my diet, started getting a lot more exercise, and religiously took my oral meds when I started having to take them after a few years. I check my blood sugar often. My diabetes is still well-controlled. I had a bout of frozen shoulder a few years ago (that got corrected with surgery) but other than that I’m fine at age 51.
My younger brother got diagnosed about ten years ago. He did nothing to change his diet (which remained awful) and stayed obese. He continued to smoke heavily and made no attempt to quit. He never even tried to get any kind of exercise. He was prescribed diabetes meds but I don’t know how good he was at taking them. Eventually he lost a big toe, and then slowly lost kidney function which eventually required him to get dialysis. He suffered two heart attacks on two separate occasions (interestingly, both attacks occurred during dialysis sessions). The second heart attack killed him. He was 47 years old.
So, that’s what can happen if you don’t get treatment.