High serum levels of glucose often mean that the body is producing insufficient amounts of insulin or the body is insensitive to the hormone. Diabetes, pancreatic cancer, pancreatitis, an overactive thyroid or severe stress can cause a high level of glucose, reports MedlinePlus.
Doctors usually test serum glucose levels to determine if an individual has diabetes, reports MedlinePlus. If serum glucose levels are high, the physician may order further tests, such as a glucose tolerance test or an HbA1c test, to determine if diabetes is the true cause. If diabetes is not the cause of the high blood sugar levels, several conditions must be considered.
An overactive thyroid gland can cause elevated serum glucose levels, according to MedlinePlus. This diagnosis is confirmed by blood tests and the presence of an enlarged thyroid gland, but a high systolic blood pressure can also confirm this. Pancreatic cancer can be a cause of high glucose levels and is readily diagnosed by abdominal palpitation, ultrasound and other scans, adds WebMD; however, pancreatic cancer is usually far progressed by the time it is suspected as a cause of elevated glucose. Likewise, various scanning techniques readily diagnose pancreatitis, but it can also be recognized by high levels of the enzymes lipase and amylase or a tissue biopsy.