SEE NORMAL BLOOD, SUGAR LEVEL

this is in mg/dL, for the SI units we in Europe have switched to decades ago 18 mg/dL = 1 mmol/L.

In 30 to 60% of those "pre-diabetics" over time will develop frank type 2 diabetes, so should start preventative physical exercise at least 150 minutes a week, and prevent overweight, if overweight lose weight, which can lower that risk by 1/3 to 1/2 (mainly depending on how much weight loss was achieved) according to large diabetes prevention trials see Implementation Science

This paper Normal Fasting Plasma Glucose and Risk of Type 2 Diabetes shows that in people having a "totally normal" fasting blood glucose of 91-99 mg/dL the chance of them developing diabetes after 15 years is 25.86% instead of 3.54 and 7.80% at lower levels, so no sharp cut off, but a sliding scale.

Original siteon Quora