Sorry, one correction: glucagon is produced in the pancreas, in the Islets of Langerhans. There are two types of islet cells: α-cells, which produce glucagon, and β-cells, which produce insulin. These cells are interspersed throughout each islet.
Prof. Bikman says that the key metabolic indicator is not insulin by itself, but the ratio of insulin to glucagon. A high ratio dictates glucose metabolism and fat-storing, whereas a low ratio dictates fatty-acid metabolism and permits fat-shedding (assuming there is excess stored fat to shed). Which is why I advocate getting the levels of both hormones tested. A low ratio (1,0-2.0) would not be so concerning, since it basically indicates ketosis and fat burning. A high ratio on a low-carb or carnivore diet would indicate some problem that would need to be addressed.