lab test results

Understanding Lab Tests and Results

Lab tests are the key to diagnose any disease or condition and they play a vital role in health care. Lab results provide detailed information about your health condition which is required by the doctor in order to make a diagnosis and decide upon a treatment. Understanding Blood Test Results and lab test results are equally important for the patient so that he can stay better informed about his condition. In many cases, test results may be affected by factors such as age, intake of medicines or herbal supplements or when the patient last ate or exercised.

Importance of Performing Lab Tests results

Lab tests are done for the following reasons:

• To identify the cause of symptoms
• To confirm a diagnosis
• To screen for a disease
• To rule out a disease or condition
• To understand the severity of a disease
• To monitor the progress of a disease
• To determine if a treatment is helping or not
• To understand how well an organ is working
• To verify specific events

Understanding the Most Common Lab Test Results

Complete Blood Count (CBC):

This is the most popular lab test that the doctor suggests during treatment. A CBC test helps to measure count of the 3 basic types of blood cells – red blood cells, white blood cells and platelets. Each of these cells has a special purpose.

White Blood Count (WBC):

This lab test results are calculates the number of white blood cells in a sample. High WBC indicates infection or leukemia while low WBC is a sign of bone marrow disease, HIV infection or enlarged spleen.

Hemoglobin (Hgb) and Hematocrit (Hct):

Hemoglobin is the amount of oxygen carrying protein contained in the red blood cells and hematocrit is the percentage of blood volume occupied by red blood cells. Low hemoglobin or hematocrit suggest anemia. High hemoglobin can occur due to lung diseases or excessive bone marrow production.

Platelet Count (PLT):

Platelets are the cells that cover up holes in your blood vessels and stop bleeding. High platelet count can be caused by cigarette smoking or excess production by bone marrow. Low platelet count can occur from acute blood loss, Immune Thrombocytopenia, drug effect, bone marrow failure due to leukemia.

Mean Corpuscular Volume (MCV):

This blood test helps to diagnose the cause of anemia. Low values may be caused by iron deficiency; high values may be caused by deficiency of vitamin B12 or folate, insufficient production in the bone marrow or recent blood loss.


Lab test for albumin and globulin helps to measure the amount and type of protein present in your blood. They act as a general index for overall health and nutrition.

Total Cholesterol:

Cholesterol is a fat-like substance found in blood. High cholesterol level in blood is a major risk factor for heart and blood vessel disease. Total cholesterol of less than 200 and LDL cholesterol of 100 of less is considered optimal.

HDL Cholesterol:

HDL or High Density Lipoprotein cholesterol is good cholesterol that protects against heart disease by removing excess cholesterol deposited in the arteries. High levels of this cholesterol are associated with low incidence of coronary heart disease.

LDL Cholesterol:

LDL or Low Density Lipoprotein is considered bad cholesterol that deposits in the arteries and increases the risk of atherosclerosis. An LDL level of less than 130 is recommended, 100 is optimal and values higher than 160 are considered high risk.


It is a type of fat found in the blood. High triglyceride levels along with high total and LDL cholesterol increases the risk of heart and circulation problems.

C Reactive Protein (CRP):

This is an indicator of inflammation. High levels of C reactive Protein is used to predict vascular diseases, heart attack and stroke.


It is an amino acid that is found in small amounts in the blood. Higher level of homocystenine is linked to increased risk of heart attack and vascular diseases. Homocysteine level also rise due to deficiency of folic acid, heredity, old age, kidney disease or certain medications.

Lipoprotein (a) or Lp (a):

Elevated levels of lipoprotein (a) is associated with premature coronary heart disease. Persons suffering from diabetes along with a high level of Lp (a) have an increased risk of asymptomatic coronary disease.


Calcium is found mostly in bones and it plays an important role in proper blood clotting and nerve and cell activity. Raised level of calcium can be a result of medications, diuretics inherited disorders of calcium handling in the kidneys or over-active parathyroid gland activity. Low calcium level can be due to metabolic disorders such as insufficient parathyroid hormone.


Phosphorus is largely found in bones. It regulates the functions of the kidney. High levels of phosphorus may be due to kidney disease and low level may be due to parathyroid disease or an over overactive parathyroid gland.


This electrolyte is controlled by the kidneys and it is important for the healthy functioning of muscles, nerves and the heart. Values above or below the expected range require medical attention.


It is also regulated by the kidneys and adrenal glands. Some of the common causes of low sodium are usage of diuretics, diabetes drugs and excessive water intake in patients with liver or heart disease.


CO2 levels determine the acid status of your blood. Low levels of CO2 can be due to increases acidity caused by kidney disease, uncontrolled diabetes, metabolic disorders or chronic hyperventilation.


Glucose test helps to measure sugar level in your blood. High values of glucose are associated with diabetes. Normal range for fasting glucose test is between 60 and 99 mg/dl.

Glycohemoglobin (Hemoglobin A1c):

This test is done in order to measure the amount of glucose attached to your red blood cells. It helps to determine the average glucose level for the last 6 to 8 weeks. A high level indicates poor diabetes control. A level of 6.5 or more indicates diabetes.

Blood Urea Nitrogen (BUN):

This is a waste product produced by the liver and flushed out by the kidneys. High values of this waste product indicate improper functioning of he kidneys BUN levels are also affected by high protein diet, strenuous exercise and pregnancy.


It is another waste product which is produced as a result of muscle breakdown. High values of creatinine in combination with elevated BUN levels indicate problems of the kidney.

Uric Acid:

It is a type of acid excreted in urine. High level of uric acid is associated with gout, arthritis and kidney problems.

Alkaline phosphatase:

It is an enzyme found in the bones and liver. High values of alkaline phosphatase are expected in children and pregnant women because they are growing. It can also indicate bone or liver damage or formation of gallstones.


This is yet another enzyme which rises in case of liver disease or obstruction of the bile ducts.


These are liver and muscle enzymes that may rise due to liver problems, hepatitis, excess alcohol consumption, muscle injury or recent heart attack.


This enzyme is present in all the cells of the body. Any factor which damages the cells will result in a rise of LDH in the blood. High levels of LDH may also occur due to improper processing of blood.


It is a pigment that is removed from the blood by the liver. It provides information about the functions of the liver and kidney and help to identify problems of bile ducts and anemia.


This enzyme is a useful indicator for heart disease and skeletal muscle disease. This is the first enzyme to be elevated after a heart attack. High CPK level in the absence of heart muscle injury indicate skeletal muscle disease.

Thyroxin (Total T4):

This test shows the total amount of T4. High levels of thyroxin may be sue to hyperthyroidism.

Free T4:

This test measures the free T4 in blood and is a more reliable test compared to Total T4 for the diagnosis of hyperthyroidism and hypothyroidism.

Total T3:

This test is ordered fir evaluating thyroid disease. T3 is a more potent and short lived version of thyroid hormone. High T3 and normal T4 means overactive thyroid or hyperthyroidism.

Free T3:

This test measures the free portion of thyroid hormone T3.

T3 Resin Uptake or Thyroid Uptake (T3RU):

This is not a thyroid test, but a test on proteins that carry thyroid hormones around in the blood stream. High test results indicate low levels of protein. This test is used to compute the free thyroxin index.

Free Thyroxin Index (FTI):

This test involves mathematical computation that estimates the free thyroxin index from T3 and T4 uptake tests. The result helps to understand how much thyroid hormone is free to work on the body.

Thyroid Stimulating Hormone (TSH):

This hormone is secreted by the pituitary gland in order to regulate the thyroid gland. High levels of TSH suggest underactive thyroid while low levels suggest overactive thyroid.

Antimicrosomal Antibody:

It is also known as anti-tissue peroxidase. This thyroid antibody becomes elevated in case of autoimmune thyroid diseases such as Hashimoto’s Thyroiditis and Graves ‘disease.


This is a hormone secreted by the beta cells of the pancreas as a response to elevated blood sugar levels. This hormone is deficient in people with type 1 diabetes and present at insufficient levels in people with type 2 diabetes. Insulin levels vary from person to person depending on an individual’s insulin sensitivity.

C- Peptide:

This hormone is a precursor of insulin. C-peptide levels correlate with insulin levels. A C-peptide test is useful in people with hypoglycemia where it can help to determine whether elevated insulin levels are a result of excessive pancreatic release of insulin or from an injection of insulin.


It is the most widely used test for estrogen measurement in women. The level of estradiol may vary according to age and normal menstrual cycles. Birth control pills or estrogen replacement therapy can affect estradiol levels.


This is the major male sex hormone; however, both men and women have detectable levels of testosterone. In men, low testosterone levels indicate reduced testicular function. It can be due to disease, damage to the testicles, aging or inadequate function of the pituitary gland. High testosterone levels can occur due to testosterone injections, testosterone secreting tumors or defects in testosterone receptor. In women, high testosterone levels can occur due to production from ovaries or the adrenal glands.

Lab Test and Blood Test Results Explained

Blood test results may be positive, negative or inconclusive. Here is a step by step guide on how to read lab results.

Positive lab test results:

A positive test result states that the condition or particular substance being tested was found. It can also mean that the level of the substance being tested for is higher or lower than normal.

Negative lab test results:

A negative test result may mean that the particular substance or condition being tested was not found. It can also mean that the substance being tested for was found but in a normal amount.

Inconclusive lab test results:

Certain tests measure the level of antibodies in response to some bacteria or viruses in the blood or other bodily fluids in order to diagnose an infection. But test results are not always clear enough to determine whether the level of antibodies in high enough to indicate an infection. In such cases, the test result is inconclusive.

False-Positive lab test results:

It is a test result that shows a disease or condition which is actually not present. A false-positive result suggests that a person has a particular disease or condition when in reality he or she does not have it.

False-Negative lab test results:

It is a test result that fails to detect the disease or condition that is being tested for even though it is present in reality. A false-negative result suggests that a person does not have a disease or condition being tested for when he or she does have it.
Blood test results are not only necessary to the doctor, as an informed patient, it is your responsibility to understand your lab test results so that you can become an active participant in your treatment and health care.

Medically Reviewed By
Dr. Kaushal M. Bhavsar (MBBS, MD)Assistant Professor in Pulmonary Medicine, GMERS Medical College, Ahmedabad