This article will try to explain routine lab tests in a very rudimentary way so that the next time your doctor tells that, for instance, you hemoglobin  is normal, you will know what that means.  Please keep in mind that the ‘normal range’ used here is specific for our hospital lab.  The ‘normal range’ parameters change from lab to lab.

Hematology examines the components of the blood.

WBC or White Blood Cells  Normal 3.7-11.0
The White Blood Cells fight infection, so this test tells your doctor if you have an infection and perhaps what kind of infection you have.  A high WBC usually indicates a bacterial infection, while a low WBC with symptoms (such as a cough or sore throat or even a mild fever) may indicate a viral infection.  A very low WBC tells your doctor that you do not have the necessary capability to fight infection so further tests will be done to determine why that is.  An extremely high WBC signals either sepsis (profound infection) or possible leukemia.  Again, further tests must be done to determine the cause.

Platelets  Normal 140-440 K/UL
Platelets are that component of the blood that helps with blood clotting.  Certain uncommon viral infections and cancers lower platelet counts, sometimes to very dangerous levels, thereby predisposing the victim to hemorrhages in the joints, vital organs or the brain.  Chemotherapy commonly causes the destruction of platelets. Dangerously low platelet levels are usually defined as anything below 10 K/UL.

Hemoglobin (HB)  12.- 16.
Hemoglobin identifies the oxygen carrying capacity of the blood and is usually associated with the number of Red Blood Cells in the body.  If Hemoglobin is low and Red Blood Cell counts (RBCs) are low,  a loss of blood somewhere in the body is suspected.  If Hemoglobin is low and RBCs normal, then low iron levels are suspected. Although obvious loss of blood from surgery or a gastrointestinal bleed or trauma are the most common causes of blood loss, other far more subtle problems may be the culprit.  Hidden bleeds and ineffective production of red blood cells by the bone marrow require multiple sophisticated tests in order to determine a diagnosis.   A dangerously low Hemoglobin is considered anything below 8.

Blood Chemistry is an important element of the standard lab tests.  These tests comprise multiple components, each telling the doctor about a specific part of the body.

Electrolytes such as Sodium, Potassium, Chloride and Carbon Dioxide along with Magnesium and Calcium govern the function of the entire body, including the contraction of muscles (particularly the heart muscle) and the ability of the body  to regulate fluid  and acid/base balance.  Too much or too little Potassium causes the heart to beat erratically resulting in death.  People taking diuretics such as Lasix or Bumex must have regular electrolyte tests to insure that potassium levels remain within a normal range.  One of the most common causes of confusion in the elderly is low sodium and chloride levels.  Extremely high levels of electrolytes may be an indication that the kidneys are failing.

Glucose is the consequence of carbohydrate metabolism.  Insulin, produced in the pancreas, is the hormone that allows the body to metabolize glucose so that it can be used for energy or stored as fat.  A normal glucose reading is between 70-125 mg/DL.  If insulin production is insufficient (known as Diabetes), then the blood glucose continues to circulate in the blood causing the body to essentially starve because glucose cannot be converted to food for the cells, while vital organs and blood vessels are destroyed by the high glucose levels.  If there is an over-supply of insulin (known as hypoglycemia) then glucose is used up too quickly and the body  succumbs to exhaustion and, in severe cases, death.   Glucose levels above 400 or below 40 are cause for alarm.

‘Cholesterol is a fat-like substance that is not used for calories.’  Fully 80% of it is produced by the liver.  There is good cholesterol (HDL) and bad cholesterol (LDL).  Both are used to determine cardiac health.  The LDL should be between 00-99.    The HDL should be between 40-59.  The higher the HDL, the better, the lower the LDL, the better.   So, if you have a LDL of 152 and a HDL of 39, you are at risk for developing heart disease.  If you have a LDL of 75 and a HDL of 110, then your risk is considerably lower.  Statin drugs such as Lipitor and Zocor help to bring down the total cholesterol count.

Triglycerides are also an indicator of heart disease.  High Triglycerides are linked to a high incidence of coronary artery pathology.

BUN (Blood Urea Nitrogen) and Creatinine are indicators of kidney function.  If the BUN is high, but the Creatinine is low, dehydration is suspected.  If the Creatinine is high and the BUN is high, kidney failure is usually the culprit.

AST/SGOT, ALT/SGPT,  Bilirubin and Alkaline Phosphatase all evaluate liver function.  When these tests produce high results, follow-up using more sophisticated tests must done in order to determine the cause of liver failure.

Albumin, Protein and A/G ratio test for kidney and liver function.  Albumin is an indicator of nutritional status.  If the Albumin is too low, malnutrition is suspected.  Albumin and Protein regulate fluid balance in the body.  When both are very low, edema (or fluid in the tissue) occurs.

EKGs tests for cardiac rhythm and poor blood flow or damage to the heart.  EKGs are only indicators of what has already occurred in the heart.  They cannot diagnose whether a coronary will take place in the future.

Urinalysis examines how well the kidneys are functioning and whether there is infection or other pathology in the bladder and kidneys.  This test can also identify liver pathology and diabetes.

If you ever have any questions about your lab test results, you should always feel free to ask your physician about them.  It is a good idea to get copies of your lab tests and to be familiar with certain numbers, such as Hemoglobin.  In the event of sudden hospitalization or illness while you are on vacation, you will be able to help your doctors determine whether new lab results are within normal limits for you.