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Donated blood is always checked for HIV, hepatitis B, hepatitis C, and sexually transmitted infections, such as syphilis, before being sent to a hospital blood bank.
Blood chemistry tests, commonly known as CHEM-7 tests, are undertaken to measure 7 different components in the blood. The results reflect the health and functioning of the different organs in our body. In simple words, CHEM-7 test provides a general idea about an individual's health. People are often advised to undergo a CHEM-7 blood test, prior to surgery. This pre-operative blood work is necessary to ensure that all organs, particularly the liver and the kidneys, are in good health before administering anesthesia.

Interpretation of CHEM-7 Test Results

Following are the blood components checked during a CHEM-7 test.
Blood Urea Nitrogen (BUN)

This component of blood gives us the level of urea nitrogen present in the blood. It is a waste product generated by the metabolism of proteins during digestion. Usually, the kidneys dispose off this chemical waste from the bloodstream as urine. The normal range of BUN values in adults is between 10 to 20 mg/dL.

High BUN Values
When CHEM-7 test detects abnormally high BUN levels, it primarily indicates that the kidneys are not functioning properly. Other medical conditions that have been correlated with increase in urea nitrogen levels are congestive heart failure, dehydration, Addison's disease, and bleeding in the gastrointestinal tract. People following a high protein diet may also exhibit higher-than-normal BUN values.

Low BUN Values
Lower than normal levels of urea nitrogen point towards serious liver damage, most probably liver failure. Inadequate protein intake or malnutrition, commonly observed in sick children, can also pull down the BUN values below the normal range. Too much fluid intake, commonly known as overhydration or water overloading, can also throw the BUN value off-balance and cause it to slide below the normal level.


Creatinine is yet another waste product generated from the breakdown of creatine―a major source of fuel for the muscles. Around 2% of creatine content in our body gets converted into creatinine everyday. The kidneys regulate creatinine levels in the blood by flushing out excess quantity through urine. Normal creatinine values are gender specific. For men, the results vary from 0.7 to 1.3 mg/dL, and for women, the normal level is between 0.6 to 1.1 mg/dL.

High Creatinine Levels
Kidney dysfunction is the primary reason behind elevated creatinine levels in the blood. Higher than normal values of creatinine are also found in people suffering from muscle problems such as rhabdomyolysis―a condition marked by abnormal breakdown of muscle fibers―or those diagnosed with blocked urinary tract due to formation of kidney stones or blood clots.

Low Creatinine Levels
In most cases, low creatinine values are not a cause for concern. It is usually harmless, and as such, it is not an issue to worry about. Pregnant women or those with reduced muscle mass, or those following a low protein diet, may also have low blood creatinine. In rare cases, it may indicate hemochromatosis or liver disorders such as hepatitis and fatty liver disease.

Carbon Dioxide (CO2)

CHEM-7 test also checks the carbon dioxide level in the blood. The carbon dioxide present in our body is in the form of bicarbonate. To be specific, over 90% of carbon dioxide in the bloodstream is bicarbonate. The remaining 10% is present as dissolved carbon dioxide or carbonic acid. The kidneys and the lungs are responsible for maintaining normal amounts of carbon dioxide in the blood. Normal values of carbon dioxide are in the range of 23 to 30 mEq/L.

High Carbon Dioxide Levels
Higher than normal levels of carbon dioxide indicate that the lungs may not be functioning properly. People diagnosed with chronic obstructive pulmonary disease (COPD) and pulmonary edema (fluid filled lungs) are likely to possess high carbon dioxide levels in the blood. Other medical conditions that can raise carbon dioxide levels are heart ailments and Cushing's disease. Frequent intake of bicarbonate-containing medication, such as antacids, can also contribute to high carbon dioxide levels in blood.

Low Carbon Dioxide Levels
Lower than normal levels of carbon dioxide has been associated with liver or kidney diseases, gastrointestinal problems, such as diarrhea, and other medical conditions like metabolic acidosis, ketoacidosis, hyperthyroidism, heart attack, Addison's disease, and uncontrolled diabetes. Excess alcohol consumption, severe dehydration, aspirin overdose, malnutrition, and hyperventilation are some other ailments that can lower carbon dioxide levels.


Measuring the glucose (sugar) component of blood is also an integral part of CHEM-7 test. Glucose levels, as we know, are controlled by insulin―a hormone secreted by the pancreas. Insulin drives excess glucose into the cells to maintain normal levels of glucose in the bloodstream. The normal blood glucose level is below 140 mg/dL 2 hours after having a meal.

High Glucose Levels
Abnormally high amount of glucose in the blood is often an indication of diabetes. This can be due to inadequate supply of insulin, or the body not responding to action of insulin. In case, diabetes is not the cause, it may indicate other endocrine disorders such as hyperthyroidism and Cushing's disease.

Low Glucose Levels
When the blood glucose levels are below the normal range, it may suggest hypothyroidism or pituitary gland disorders such as hypopituitarism. Overdose of diabetic medication can also lower the glucose level below the normal range.

Serum Chloride

This test estimates the amount of chloride present in the clear fluid part of the blood. Chloride is an electrolyte that helps preserve the appropriate balance of fluids. It also assists in regulating the correct acid/base equilibrium. Normal range of serum chloride falls between 96 to 100 mEq/L.

High Chloride Levels
Higher than normal chloride levels in blood may signify kidney problems such as renal tubular acidosis―a condition in which the kidneys find it difficult to filter acids from the blood. Other conditions that can lead to higher-than-normal chloride levels are diarrhea, metabolic acidosis, and bromide poisoning.

Low Chloride Levels
Abnormally high amount of fluid loss due to excessive sweating or vomiting can disturb the electrolyte balance and cause chloride to slide below the normal level. People diagnosed with heart failure, metabolic alkalosis, respiratory acidosis or Addison's disease may also exhibit lower chloride levels in blood.

Serum Potassium

This is yet another blood component measured by a CHEM-7 test. It checks the level of potassium in the liquid part of the blood. Potassium is important for the proper working of muscles and nerve activity. It helps control nerve signaling to muscle cells. This allows the desired muscle group to relax and stretch whenever necessary. The heart also requires potassium to beat at a normal rhythm. Normal values of serum potassium fall between 3.5 to 5.2 mEq/L.

High Potassium Levels
Too much potassium in the blood, also known as hyperkalemia, may suggest damage to the kidneys. This can make the kidneys incapable of regulating potassium levels. Acid buildup in the blood and body fluids due to medical conditions like metabolic or respiratory acidosis can also result in hyperkalemia. Crushed tissue injuries, severe burns, and diabetic ketoacidosis are some of the conditions that cause potassium to leave body cells and enter the blood stream. This may also cause high blood potassium levels. Individuals who take medication, like ACE inhibitor, to treat high blood pressure or diuretic drugs to flush off excess water may also exhibit high potassium in blood.

Low Potassium Levels
Lower than normal levels of potassium have been usually associated with chronic diarrhea, vomiting, use of diuretics, and inadequate potassium in the diet. Rare causes of abnormally low potassium levels include renal tubular acidosis―a condition in which the kidneys fail to filter excess amount of acids from the blood.

Serum Sodium

Checking the amount of sodium present in the watery part of blood is also an integral part of CHEM-7 test. Sodium is important to maintain fluid levels in the body as well as regulate transmission of nerve impulses and muscle contraction. Normal values of serum sodium fall between 135 to 145 mEq/L.

High Sodium
Dehydration, following a high-sodium diet, adrenal gland problems, use of birth control pills, and medical conditions, like diabetes insipidus (a condition in which the kidneys find it difficult to conserve fluids and is marked by excretion of large amounts of urine) are some of the factors that can lead to high sodium levels in the blood.

Low Sodium
Diarrhea, vomiting, excessive water intake and use of diuretic drugs are some of the common reasons behind lower than normal sodium levels in the blood. People suffering from hypothyroidism, kidney problems, cirrhosis, and adrenal gland disorders may also have low blood sodium.

On the whole, when an overview of blood chemistry is needed to check the health of different organs or to diagnose a particular condition, the doctor will perform a CHEM-7 test.