Blood chemistry is the chemical composition of the blood. The levels of various substances in the blood can provide clues to a patient's condition, ranging from the presence of a liver disorder to a pregnancy. Routine bloodwork to check blood chemistry is often a part of a diagnostic workup, with the blood being analyzed to check for specific elements which could contribute clues to the diagnosis. Doctors rely on information about normal ranges of things like proteins and lipids to read the blood analysis.
A wide variety of things can be examined in a blood chemistry test. The basic composition of the blood in the form of numbers of white blood cells, red blood cells, and platelets is usually a routine part of the test. In the hematocrit reading, the technician doing the analysis looks at the percentage of red blood cells in the blood. Technicians also look at the amount of hemoglobin, the mean corpuscular volume, meaning the size of red blood cells, and the mean corpuscular hemoglobin, the average weight of the hemoglobin in a red blood cell.
Blood tests can also look for specific enzymes, such as a family of enzymes which indicate the level of liver function. Levels of alkaline phosphatase, serum Glutamic-Pyruvic Transaminase (sGPT), and serum Glutamic-Oxaloacetic Transaminase (sGOT) can reveal information about how well the liver is functioning. Presence of electrolytes like sodium, potassium, chloride, and calcium can also be measured in a blood analysis, along with levels of proteins and lipids in the blood.
Specific tests can search for nitrogen elements including Blood Urea Nitrogren (BUN), uric acid, and creatinine, along with thyroid hormones which can be used to assess the level of thyroid function. In a glucose fasting test, the patient fasts for a set period of time before being tested for glucose to look for signs of diabetes. The analysis of any blood chemistry test also usually includes a discussion of the ratios of the various substances in the blood, along with information about normal ratio ranges which can be used to evaluate the results.
Everyone's blood is slightly different, and sometimes people have readings which fall outside the normal range without being a cause for concern. Doctors have to evaluate these cases on an individual basis to determine how the result should be addressed. Blood chemistry is usually one of the key steps in a differential diagnosis, in which a doctor or medical team explores all of the potential causes for a patient's condition and uses medical testing to rule out causes in order to arrive at a diagnosis.