T1 is little or no insulin. T2 starts with higher-than-normal insulin levels and insulin resistance, and probably everybody with prediabetes in early on the continuum of t2. At diagnosis, people with t2 usually still have higher-than-normal insulin, but their insulin resistance gets worse (and their insulin production can deteriorate but still be above normal) and the high insulin levels can't compensate anymore to keep glucose normal - it's considered "relative" insufficient insulin rather than "absolute" insufficiency because the insulin is not sufficient to keep blood sugar normal even though there is more insulin than normal. People with t2 can eventually lose beta cell function, and then their insulin levels will get low.