Formulating a diagnosis is an ongoing, dynamic and flexible process. Your health care practitioner may start with a medical history, which includes aspects of the present illness, past illnesses, surgeries, medications, social habits such as smoking. This is followed by a physical exam. Based on these findings, you may undergo laboratory and imaging studies to clarify or establish the diagnosis. A common laboratory panel performed on your blood is called the basic metabolic panel, which includes the glucose, BUN and creatinine tests.
Basic Metabolic Panel
The basic metabolic panel includes measures of the positively charged electrolytes sodium and potassium; the negatively charged chloride and bicarbonate; two chemicals largely linked to kidney function, BUN and creatinine; and the sugar glucose. Some labs may report other chemicals to your physician as well. High and low levels of these chemicals can help to establish a diagnosis.
Glucose
Large chains of carbohydrates such as those in bread and pasta are broken down by your body into simple sugars, particularly glucose, in your small intestine. Glucose enters your cells and is broken down further by special enzymes to make the energy carrier of the cell, adenosine triphosphate (ATP). On the basic metabolic panel, glucose is important because both high and low levels cause problems. Extremely elevated levels of glucose make your blood viscous like syrup and interfere with blood flow and oxygen exchange. Moderately high levels maintained over a long time, as in diabetes, damage your proteins and blood vessels, leading to organ damage. Low levels of glucose deprive your cells of energy and can lead to fatigue, fainting, coma or death.
BUN
Blood urea nitrogen (BUN) is a waste product created by your liver from the breakdown of protein. It travels through the blood and is excreted by your kidneys. Even though it is a waste product, it is not toxic. A low level of BUN is generally of no significance. It can be caused by low protein intake, liver problems, pregnancy, over-hydration and excessive alcohol. High levels are more often associated with disease. A high BUN reading is found with dehydration, kidney problems and gastrointestinal bleeding. Increased breakdown of proteins in high-protein diets, intravenous feeding, burns, steroid use or high fevers can also increase your BUN levels.
Creatinine
Creatinine is a sensitive indicator of your kidney function. Creatinine is made from creatine phosphate, which is found in high levels in your muscle and nerve tissue. Creatine functions to quickly restore ATP levels. In contrast, its breakdown product, creatinine, has no function, and is excreted by your kidneys. High levels usually indicate kidney disease. It can also be elevated in your blood by substances that interfere with its excretion, such as the antibiotic trimethoprim or the stomach medicine cimetidine.
References
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci, et al.; 17th Ed.; 2008
- "Henry's Clinical Diagnosis and Management by Laboratory Methods"; Richard A. McPherson, et al.; 21st Ed.; 2006
