Low blood glucose. There are excellent physiological mechanisms, even in starvation to prevent this. The commonest cause therefore is drug induced, especially with drugs taken to treat diabetes such as oral hypoglycaemic agents and insulin. Pathologies affecting the livers ability to manufacture glucose from glycogen are the other main cause. Hypoglycaemia can be life threatening if not corrected. Certain genetic diseases can cause significant hypoglycaemia in the neonate (eg familial hyperinsulinaemic hypoglycaemia) which can be extremely important to recognise so as to prevent brain damage by appropriate treatment.
If patients are able to eat and drink, a suitable sugary carbonated drink will suffice (can of Coke contains 30-40g sugar).
If oral route not available, 10% glucose can be given if hypoglycaemia is not severe (500ml contains 50g sugar, but due to volume, it takes time to administer). This is a hyperosmolar solution and can be irritant to the veins if administered quickly.
In urgent situations, e.g. hypoglycaemic coma, 50ml of 50% glucose should be administered. 50% glucose is extremely sticky and viscous and even more irritant than 10% glucose. Painful phlebitis after administration is very common.