In children who are aged greater than 48 hours, serum glucose on average ranges from 70 to 100 mg/dL (3.9-5.5 mmol/L), similar to adults, with hypoglycemia being far less common. Diagnostic approach
The most reliable method of identifying hypoglycemia is through identifying Whipples triad. The components of Whipples triad are a blood sugar level below 70 mg/dL (3.9 mmol/L), symptoms related to low blood sugar, and improvement of symptoms when blood sugar is restored to normal. Identifying Whipples triad in a patient helps to avoid unnecessary diagnostic testing and decreases healthcare costs.In those with a history of diabetes treated with insulin, glinides, or sulfonylurea, who demonstrate Whipples triad, it is reasonable to assume the cause of hypoglycemia is due to insulin, glinides, or sulfonylurea use. In those without a history of diabetes with hypoglycemia, further diagnostic testing is necessary to identify the cause. Testing, during an episode of hypoglycemia, should include the following:

Plasma glucose level, not point-of-care measurement
Insulin level
C-peptide level
Proinsulin level
Beta-hydroxybutyrate level
Oral hypoglycemic agent screen
Response of blood glucose level to glucagon
Insulin antibodiesIf necessary, a diagnostic hypoglycemic episode can be produced in an inpatient or outpatient setting. This is called a diagnostic fast, in which a patient undergoes an observed fast to cause a hypoglyemic episode, allowing for appropriate blood work to be drawn.
Addisons disease is associated with chronically low levels of the stress hormone cortisol, which leads to decreased glucose production.Hypopituitarism, leading to decreased growth hormone, is another cause of hypoglycemia in children, particularly with long periods of fasting or increased exercise. Inborn errors of metabolism
Briefly, inborn errors of metabolism are a group rare of genetic disorders that are associated with the improper breakdown or storage of proteins, carbohydrates, or fatty acids. Inborn errors of metabolism may cause infant hypoglycemia, and much less commonly adult hypoglycemia. Disorders that are related to the breakdown of glycogen, called glycogen storage diseases, may cause hypoglycemia. Normally, breakdown of glycogen leads to increased glucose levels, particularly in a fasting state. In glycogen storage diseases however, glycogen cannot be properly broken-down, leading to inappropriately decreased glucose levels in a fasting state, and thus hypoglycemia. The glycogen storage diseases associated with hypoglycemia include type 0, type I, type III, and type IV, as well as Fanconi syndrome. Insulinomas
A primary B-cell tumor, such as an insulinoma, is associated with hypoglycemia. This is a tumor located in the pancreas. An insulinoma produces insulin, which in turn decreases glucose levels, causing hypoglycemia. Normal regulatory mechanisms are not in place, which prevent insulin levels from falling during states of low blood glucose. During an episode of hypoglycemia, plasma insulin, C-peptide, and proinsulin will be inappropriately high. Non-B cell tumors
Hypoglycemia may occur in people with non-B cell tumors such as hepatomas, adrenocorticoid carcinomas, and carcinoid tumors.