Laboratory tests are tools helpful in evaluating the health status of an individual. It is important to realize that
laboratory results may be outside of the so-called "normal range" for many reasons. These variations may be
due to such things as race, dietetic preference, age, sex, menstrual cycle, degree of physical activity,
problems with collection and/or handling of the specimen, non-prescription drugs (aspirin, cold medications,
vitamins, etc.), prescription drugs, alcohol intake and a number of non-illness-related factors, Any unusual or
abnormal results should be discussed with your physician. It is not possible to diagnose or treat any disease or
problem with this blood test alone. It can, however, help you to learn more about your body and detect potential
problems in early stages when treatment or changes in personal habits can be most effective.
Almost all labs set the normal result range for a particular test so that 95% of healthy patients fall within the
normal range. That means that 5% of healthy patients fall outside of the normal range, even when there is
nothing wrong with them. Thus an abnormal test does not necessarily mean that there is something wrong with
you. Statistically if you have 20 or 30 individual tests run as part of a panel, chances are 1 or 2 will be slightly
outside the normal range. Part of what you see your doctor for is to interpret whether or not these changes are
This review is a brief summary and is not intended to be comprehensive or replace discussion of
your results with your health care team.
Glucose: This is a measure of the sugar level in your blood. High values are associated with eating before the
test, and diabetes.
The normal range for a fasting glucose is 60 -99 mg/dl. According the the 2003 ADA criteria, diabetes is
diagnosed with a *fasting* plasma glucose of 126 or more. A precursor, Impaired Fasting Glucose (IFG) is
defined as reading of fasting glucose levels of 100 - 125. Sometimes a glucose tolerance test, which involves
giving you a sugary drink followed by several blood glucose tests, is necessary to properly sort out normal from
IFG from diabetes.
Be aware that variations in lab normals exist. Also, Europeans tend to use a 2 hour after eating definition of
diabetes rather than a fasting glucose. Using the European standards tends to increase the number of people
who are classified as having diabetes.
Electrolytes: These are your potassium, sodium, chloride, and CO2 levels.
Potassium is controlled very carefully by the kidneys. It is important for the proper functioning of the nerves and
muscles, particularly the heart. Any value outside the expected range, high or low, requires medical evaluation.
This is especially important if you are taking a diuretic (water pill) or heart pill (Digitalis, Lanoxin, etc.).
Sodium is also regulated by the kidneys and adrenal glands. There are numerous causes of high and low
sodium levels, but the most common causes of low sodium are diuretic usage, diabetes drugs like
chlorpropamide, and excessive water intake in patients with heart or liver disease.
CO2 reflects the acid status of your blood. Low CO2 levels can be due to either to increased acidity from
uncontrolled diabetes, kidney disease, metabolic disorders, or low CO2 can be due to chronic hyperventilation.
Blood Urea Nitrogen (BUN) is a waste product produced in the liver and excreted by the kidneys. High values
may mean that the kidneys are not working as well as they should. BUN is also affected by high protein diets
and/or strenuous exercise which raise levels, and by pregnancy which lowers it.
Creatinine is a waste product largely from muscle breakdown. High values, especially with high BUN levels,
may indicate problems with the kidneys..
Uric Acid is normally excreted in urine. High values are associated with gout, arthritis, kidney problems and the
use of some diuretics.
AST, ALT, SGOT, SGPT, and GGT and Alkaline Phosphatase are abbreviations for proteins called enzymes
which help all the chemical activities within cells to take place. Injury to cells release these enzymes into the
blood. They are found in muscles, the liver and heart. Damage from alcohol and a number of diseases are
reflected in high values.
Alkaline phosphatase is an enzyme found primarily in bones and the liver. Expected values are higher for
those who are growing (children and pregnant women) or when damage to bones or liver has occurred or with
gallstones. Low values are probably not significant.
GGT is also elevated in liver disease, particularly with obstruction of bile ducts. Unlike the alkaline
phosphatase it is not elevated with bone growth or damage.
AST/SGOT , ALT/ SGPT are also liver and muscle enzymes. They may be elevated from liver problems,
hepatitis, excess alcohol ingestion, muscle injury and recent heart attack.
LDH is the enzyme present in all the cells in the body. Anything which damages cells, including blood drawing
itself, will raise amounts in the blood. If blood is not processed promptly and properly, high levels may occur. If
all values except LDH are within expected ranges, it is probably a processing error and does not require
Bilirubin: is a pigment removed from the blood by the liver. Low values are of no concern. If slightly elevated
above the expected ranges, but with all other enzymes (LDH, GOT, GPT, GGT) within expected values, it is
probably a condition known as Gilbert’s syndrome and is not significant
CPK is an enzyme which is very useful for diagnosing diseases of the heart and skeletal muscle. This enzyme
is the first to be elevated after a heart attack (3 to 4 hours). If CPK is high in the absence of heart muscle
injury, this is a strong indication of skeletal muscle disease.
Albumin and Globulin measure the amount and type of protein in your blood. They are a general index of
overall health and nutrition. Globulin is the "antibody" protein important for fighting disease.
A/G Ratio is the mathematical relationship between the above.
Cholesterol is a fat-like substance in the blood which, if elevated has been associated with heart disease.
Total Cholesterol: A high cholesterol in the blood is a major risk factor for heart and blood vessel disease.
Cholesterol in itself is not all bad, in fact, our bodies need a certain amount of this substance to function
properly. However, when the level gets too high, vascular disease can result. A total cholesterol of less than
200, and an LDL Cholesterol of 100 or less is considered optimal by the National Heart, Lung, and Blood
Institute. The levels that your doctor will recommend depend upon whether you are at high risk for
As the level of blood cholesterol increases, so does the possibility of plugging the arteries due to cholesterol
plaque build-up. Such a disease process is called "hardening of the arteries" or atherosclerosis. When the
arteries feeding the heart become plugged, a heart attack may occur. If the arteries that go to the brain are
affected, then the result is a stroke.
There are three major kinds of cholesterol, High Density Lipoprotein (HDL) , Low Density Lipoprotein (LDL),
and Very Low Density Lipoprotein (VLDL).
LDL Cholesterol is considered "bad cholesterol" because cholesterol deposits form in the arteries when LDL
levels are high. An LDL level of less than 130 is recommended, 100 is optimal, values greater than 160 are
considered high risk and should be followed up by your physician. Those persons who have established
coronary or vascular disease may be instructed by their doctor to get their LDL Cholesterol well below 100.
You should ask your doctor which LDL target he or she wants for you. There are two ways to report LDL. The
most common is simply an estimate calculated from the Total Cholesterol, HDL, and triglycerides results. This
may say "LDL Calc" . A directly measured LDL Cholesterol is usually more accurate, but more expensive and
may require that your doctor specify the direct LDL.
HDL cholesterol is a ‘good cholesterol’ as it protects against heart disease by helping remove excess
cholesterol deposited in the arteries. High levels seem to be associated with low incidence of coronary heart
Triglyceride is fat in the blood which, if elevated, has been associated with heart disease, especially if over
500 mg. High triglycerides are also associated with pancreatitis. Triglyceride levels over 150 mg/dl may be
associated with problems other than heart disease. Ways to lower triglycerides: 1) weight reduction, if
overweight; 2) reduce animal fats in the diet: eat more fish; 3) take certain medications your physician can
prescribe; 4) get regular aerobic exercise; 5) decrease alcohol and sugar consumption—alcohol and sugar
are not fats, but the body can convert them into fats then dump those fats into your blood stream 6) restrict
calories - carbohydrates are converted to triglycerides when eaten to excess.
VLDL (very low density lipoprotein) is another carrier of fat in the blood.
Cardiac Risk Factors
C Reactive Protein (CRP): This is a marker for inflammation. Traditionally it has been used to assess
inflammation in response to infection. However we use a highly sensitive C Reactive Protein which is useful in
predicting vascular disease, heart attack or stroke.. The best treatment for a high C reactive protein level has
not yet been defined, however statin drugs, niacin, weight loss, quitting smoking, and exercise all appear to
improve C- Reactive Protein
Homocysteine: Homocysteine is an amino acid that is normally found in small amounts in the blood. Higher
levels are associated with increased risk of heart attack and other vascular diseases. Homocysteine levels
may be high due to a deficiency of folic acid or Vitamin B12, due to heredity, older age, kidney disease, or
certain medications. Men tend to have higher levels. Our lab normals are 4 - 15 micromole/l , but if you have
had previous vascular disease we may recommend medications to reduce it below 10. You can reduce your
homocysteine level by eating more green leafy vegetables and fortified grain products or cereals. The usual
treatment is folic acid with or without Vitamin B-12.
Lipoprotein (a) or Lp(a) : Elevated lipoprotein(a) (Lp[a]) concentrations are associated with premature
coronary heart disease (CHD). The exact mechanism is not yet clear, but it appears that there is a strong
genetic component to elevated Lp(a) levels that correlates with coronary disease. Persons with diabetes and
a high Lp(a) level appear to be at increased risk of asymptomatic coronary disease.
Note that a few insurance companies refuse to pay for cardiac risk factor testing. As of this writing, Aetna
stands out as a company that refuses to cover testing for homocysteine or Lp(a) on the basis that it is
"experimental" or "investigational". We have asked for a comprehensive review of their policy since it deviates
from the norm.
Calcium is controlled in the blood by the parathyroid glands and the kidneys. Calcium is found mostly in bone
and is important for proper blood clotting, nerve, and cell activity. An elevated calcium can be due to
medications such as thiazide type diuretics, inherited disorders of calcium handling in the kidneys, or excess
parathyroid gland activity or vitamin D. Low calcium can be due to certain metabolic disorders such as
insufficient parathyroid hormone; or drugs like Fosamax or furosemide type diuretics.
Calcium is bound to albumin in the blood, so a low albumin level will cause the total calcium level in the blood
to drop. You doctor can easily determine if this is significant or not.
Phosphorus is also largely stored in the bone. It is regulated by the kidneys, and high levels may be due to
kidney disease. When low levels are seen with high calcium levels it suggests parathyroid disease, however
there are other causes. A low phosphorus, in combination with a high calcium, may suggest an overactive
There are 2 types of thyroid hormones easily measurable in the blood, thyroxine (T4) and triiodothyronine (T3).
For technical reasons, it is easier and less expensive to measure the T4 level, so T3 is usually not measured
on screening tests.
Please be clear on which test you are looking at. We continue to see a tremendous amount of confusion
among doctors, nurses, lab techs, and patients on which test is which. In particular, the "Total T3", "Free T3"
and "T3 Uptake tests" are very confusing, and are not the same test.
Thyroxine (T4) . This shows the total amount of the T4. High levels may be due to hyperthyroidism, however
technical artifact occurs when estrogen levels are higher from pregnancy, birth control pills or estrogen
replacement therapy. A Free T4 (see below) can avoid this interference.
T3 Resin Uptake or Thyroid Uptake. This is a test that confuses doctors, nurses, and patients. First, this is not
a thyroid test, but a test on the proteins that carry thyroid around in your blood stream. Not only that, a high test
number may indicate a low level of the protein! The method of reporting varies from lab to lab. The proper use
of the test is to compute the free thyroxine index.
Free Thyroxine Index (FTI or T7) : A mathematical computation allows the lab to estimate the free thyroxine
index from the T4 and T3 Uptake tests. The results tell us how much thyroid hormone is free in the blood
stream to work on the body. Unlike the T4 alone, it is not affected by estrogen levels.
Free T4 : This test directly measures the free T4 in the blood rather than estimating it like the FTI. It is a more
reliable , but a little more expensive test. Some labs now do the Free T4 routinely rather than the Total T4.
Total T3: This is usually not ordered as a screening test, but rather when thyroid disease is being evaluated. T3
is the more potent and shorter lived version of thyroid hormone. Some people with high thyroid levels secrete
more T3 than T4. In these (overactive) hyperthyroid cases the T4 can be normal, the T3 high, and the TSH low.
The Total T3 reports the total amount of T3 in the bloodstream, including T3 bound to carrier proteins plus
freely circulating T3.
Free T3: This test measures only the portion of thyroid hormone T3 that is "free", that is, not bound to carrier
Thyroid Stimulating Hormone (TSH) : This protein hormone is secreted by the pituitary gland and regulates the
thyroid gland. A high level suggests your thyroid is underactive, and a low level suggests your thyroid is
Glycohemoglobin (Hemoglobin A1 or A1c, HbA1c) : Glycohemoglobin measures the amount of glucose
chemically attached to your red blood cells. Since blood cells live about 3 months, it tells us your average
glucose for the last 6 - 8 weeks. A high level suggests poor diabetes control. Standardization for
glycohemoglobin from lab to lab is poor, and you cannot compare a test from different labs unless you can
verify the technique for measuring glycohemoglobin is the same. The only exception is if your lab is
standardized to the national DCCT referenced method. You can ask your lab if they use a DCCT referenced
FYI, at Amarillo Medical Specialists we do use a test method that is DCCT referenced.
Insulin : Insulin is secreted by the pancreas in response to eating or elevated blood sugar. It is deficient in
persons with type 1 diabetes, and present at insufficient levels in persons with type 2 diabetes. The natural
evolution of type 2 diabetes causes insulin levels to fall from high levels to low levels over a course of years.
Thus insulin levels in persons with type 1 and type 2 diabetes overlap significantly, and insulin levels are not
very useful in determining type 1 vs type 2. Insulin levels vary widely from person to person depending upon an
individuals insulin sensitivity (or conversely, their insulin resistance.) Insulin levels also vary widely according to
when the last meal occurred. Insulin resistance is a risk factor for coronary disease, thus assessing an
individual's insulin resistance may have some value using the HOMA-IR calculation. Insulin levels are also
elevated in patients with true hypoglycemia, however the interpretation of these levels is difficult. Insulin levels,
when measured by itself at a random time is rarely useful.
C-peptide : This is a fragment cleaved off of the precursor of insulin (pro-insulin) when insulin is manufactured
in the pancreas. C-peptide levels usually correlate with the insulin levels, except when people take insulin
injections. When a patient is hypoglycemic, this test may be useful to determine whether high insulin levels are
due to excessive pancreatic release of insulin, or from an injection of insulin.
Estradiol : This is the most commonly measured type of estrogen measured. In women it varies according to
their age, and whether they are having normal menstrual cycles. Hormone levels are also changed when taking
birth control pills or estrogen replacement.
Complete Blood Count (CBC)
The CBC typically has several parameters that are created from an automated cell counter. These are the
White Blood Count (WBC) is the number of white cells. High WBC can be a sign of infection. WBC is also
increased in certain types of leukemia. Low white counts can be a sign of bone marrow diseases or an
enlarged spleen. Low WBC is also found in HIV infection in some cases. (ed. note: The vast majority of low
WBC counts in our population is NOT HIV related.)
Hemoglobin (Hgb) and Hematocrit (Hct) : The hemoglobin is the amount of oxygen carrying protein contained
within the red blood cells. The hematocrit is the percentage of the blood volume occupied by red blood cells. In
most labs the Hgb is actually measured, while the Hct is computed using the RBC measurement and the MCV
measurement. Thus purists prefer to use the Hgb measurement as more reliable. Low Hgb or Hct suggest an
anemia. Anemia can be due to nutritional deficiencies, blood loss, destruction of blood cells internally, or
failure to produce blood in the bone marrow. High Hgb can occur due to lung disease, living at high altitude, or
excessive bone marrow production of blood cells.
Mean Corpuscular Volume (MCV) - This helps diagnose a cause of an anemia. Low values suggest iron
deficiency, high values suggest either deficiencies of B12 or Folate, ineffective production in the bone marrow,
or recent blood loss with replacement by newer (and larger) cells from the bone marrow.
Platelet Count (PLT) : This is the number of cells that plug up holes in your blood vessels and prevent bleeding.
High values can occur with bleeding, cigarette smoking or excess production by the bone marrow. Low values
can occur from premature destruction states such as Immune Thrombocytopenia (ITP), acute blood loss, drug
effects (such as heparin) , infections with sepsis, entrapment of platelets in an enlarged spleen, or bone
marrow failure from diseases such as myelofibrosis or leukemia. Low platelets also can occur from clumping
of the platelets in a lavender colored tube. You may need to repeat the test with a green top tube in that case.
Urine tests are typically evaluated with a reagent strip that is briefly dipped into your urine sample. The
technician reads the colors of each test and compares them with a reference chart. These tests are semi-
quantitative; there can be some variation from one sample to another on how the tests are scored.
pH : This is a measure of acidity for your urine.
Specific Gravity (SG) : This measures how dilute your urine is. Water would have a SG of 1.000 . Most urine is
around 1.010, but it can vary greatly depending on when you drank fluids last, or if you are dehydrated.
Glucose: Normally there is no glucose in urine. A positive glucose occurs in diabetes. There are a small
number of people that have glucose in their urine with normal blood glucose levels, however any glucose in the
urine would raise the possibility of diabetes or glucose intolerance.
Protein: Normally there is no protein detectable on a urinalysis strip. Protein can indicate kidney damage,
blood in the urine, or an infection. Up to 10% of children can have protein in their urine. Certain diseases
require the use of a special, more sensitive (and more expensive) test for protein called a microalbumin test. A
microalbumin test is very useful in screening for early damage to the kidneys from diabetes, for instance.
Blood: Normally there is no blood in the urine. Blood can indicate an infection, kidney stones, trauma, or
bleeding from a bladder or kidney tumor. The technician may indicate whether it is hemolyzed (dissolved
blood) or non-hemolyzed (intact red blood cells). Rarely, muscle injury can cause myoglobin to appear in the
urine which also causes the reagent pad to falsely indicate blood.
Bilirubin: Normally there is no bilirubin or urobilinogen in the urine. These are pigments that are cleared by the
liver. In liver or gallbladder disease they may appear in the urine as well.
Nitrate: Normally negative, this usually indicates a urinary tract infection.
Leukocyte esterase: Normally negative. Leukocytes are the white blood cells (or pus cells). This looks for white
blood cells by reacting with an enzyme in the white cells. White blood cells in the urine suggests a urinary tract
Sediment: Here the lab tech looks under a microscope at a portion of your urine that has been spun in a
centrifuge. Items such as mucous and squamous cells are commonly seen. Abnormal findings would include
more than 0-2 red blood cells, more than 0-2 white blood cells, crystals, casts , renal tubular cells or bacteria.
(Bacteria can be present if there was contamination at the time of collection.)
Blood Test Results Explained