Small molecule kinase inhibitors (SMKIs) are a class of therapeutic drugs that target protein kinases in diseases such as cancer. SMKIs are often designed to inhibit kinases involved in cell proliferation, but these drugs alter cell metabolism and endocrine control of organismal metabolism. SMKI treatment in diabetic cancer patients reveals that certain SMKIs improve blood glucose control and can mitigate insulin dependence or diabetic medication requirements in both Type 1 Diabetes (T1D) and Type 2 Diabetes (T2D). Certain SMKIs can preserve functional β-cell mass and increase insulin secretion or insulin sensitivity. It is not yet clear why different SMKIs can have opposing effects on insulin and blood glucose. Understanding the therapeutic effects of these drugs in T1D and T2D is complicated by overlapping off-target effects of SMKIs. The potency of inhibition of the intended protein kinase and inhibition of multiple off-target kinases may underpin conflicting reports of how certain SMKIs alter blood glucose and insulin. We summarize the effects of SMKIs on the intended and off-target kinases that can alter blood glucose and insulin, including c-Abl, c-Kit, EGFR, and VEGF. Inhibition of PDGFRβ consistently lowers blood glucose in T1D and T2D. The effects of SMKIs on the kinases that regulate immune pathways, such as BTK and RIPKs mediate many of the diverse effects of these drugs on metabolism. We highlight that inhibition of RIPK2 by SMKIs is a central node in metabolism that influences key metabolic pathways including lipolysis, blood glucose control, insulin secretion, and insulin resistance.