What happens if your insulin levels are too low?

Insulin is a hormone that controls blood sugar and produced from the pancreas. If it becomes too low, your blood sugar will rise causing hyperglycemia. If it is too high on the other hand, it will cause your blood sugar to go down (hypoglycemia).

there is a LOW BLOOD SUGAR also ..........................................

How low?  It COULD be an indication that you are developing type 1 diabetes mellitus.  (In type 1 diabetes your body's own immune system sets out to destroy the insulin-producing cells of the pancreas.  Type 2 diabetics tend to produce a higher level of insulin as their body's cells have become resistant to the effects of the insulin that is currently being produced by the pancreas.)

It COULD also be that you are the type of person that 'under eats'. i.e. if you're on a very strict diet ... or starving.