Common Lab Test Questions Answered

If you have a list of laboratory test results, you may feel overwhelmed by the amount of information you’re looking at. What do the various abbreviations mean in lab test reports? And how will my healthcare professional use the information to help spot potential health issues and to guide me in maintaining good health? Here’s a look at some common lab test questions and answers to help empower and guide you in your care.

Why does my provider not say a normal or abnormal range? Isn't the range that is printed a normal range?

The ranges that are printed on lab test reports are actually statistical results. They describe the values that one might find in 95 percent of a population. So think of 200 healthy adults. In that group, 190 of those 200 people will have values that fall within the printed range—5 will have values that are too low and 5 that are too high. All of these people are healthy yet 10 adults will have values that lie outside mathematics. So laboratory scientists call this range a reference range or reference interval, not a normal range.

To further complicate the issue is that different laboratories will have different instruments, different methods and techniques, and the like so each laboratory staff must develop their own unique set of these reference ranges. You must compare your lab test results to the reference interval developed by that laboratory staff. To increase the quality of your test results, always go to the same laboratory and follow the directions carefully.

What does a CBC (complete blood count) measure?

A CBC, or complete blood count is a collection of blood tests looking at the cells that are found in the peripheral blood. This is often done during your annual check-up or when you're feeling unwell and the cause isn’t clear.

This test looks closely at the three main types of cells in your blood:

• Red blood cells (erythrocytes), which carry oxygen
• White blood cells (leukocytes), which help fight infection
• Platelets (thrombocytes), which help your blood clot

By measuring the levels and types of these cells in lab test results, a CBC can help your healthcare provider spot signs of many conditions including:

• Viral or bacterial infections
• Certain types of anemia
• Inflammation
• Signs of incorrect bleeding or clotting
• Early signs of various organ or immune system problems

A CBC is a helpful first step in understanding what might be going on with your health and guiding next steps in care.

What is a normal red blood cell count, hemoglobin or hematocrit level?

For the red blood cells, the oldest tests are the red blood cell count (RBC), followed by the hemoglobin (HGB or HB) and then hematocrit (HCT). The red blood cell count is exactly what its name says. A specific volume of cells is counted. While important, the red cells exist to carry hemoglobin and to keep it functional, so just knowing the number does not help to clarify if there are issues with the red cells’ function. Because red blood cells exist to bring oxygen to the tissues and to bring carbon dioxide back to the lungs to be expelled, the number of cells will vary by age, gender, activity need, and several other factors. Look to the right of your result, and you will see reference ranges for adult males and females. Hospitals that specialize in treating children have ranges that vary by day for newborns, weeks for infants, and years for children.

Hemoglobin HGB is the protein that fills approximately one third of the volume of the average red cell. Its function is to bring oxygen from the lungs to the tissues where it is delivered to the cells in exchange for the waste product, carbon dioxide. Although hemoglobin levels vary due to various factors including those mentioned before, acceptable adult hemoglobin ranges printed on your report will typically list just adult males and females. Decreased hemoglobin levels may be an indicator of a range of medical conditions from poor diet to types of malignancies that impact blood production and many other situations. Conversely, increased hemoglobin levels may indicate a range of conditions, from dehydration to a condition in the bone marrow called polycythemia vera. Additional factors that push your hemoglobin levels outside what’s considered an acceptable range can include:

• Various medications
• Physical activity or exercise
• Your diet
• Stress
• Altitude

The hematocrit level on your blood test results is the percentage of your blood that is comprised of red blood cells. Since this is a volume result, situations in which you have fewer red cells or cells which contain lesser amounts of hemoglobin so that the cells take up less space or if the cells themselves are smaller than they should be will give you a lower result. There are literally dozens of situations in which these situations occur. An increased hematocrit suggests more cells than usual or cells that might be larger than expected. Increased hematocrit values can be seen in situations in which there is a greater need for hemoglobin. Since the volume of red cells is in part controlled by the ability of the hemoglobin to pick up oxygen from the lungs, any condition that makes that hard, such as asthma or smoking, and difficulty in moving those cells around, such as cardiac issues, will be considered by your provider. As with the red blood cell count and hemoglobin value, the acceptable range for hematocrit levels may vary depending on your age and gender.

These three tests together give your provider a sense of your body’s ability to make and maintain functional red blood cells. Additional tests found in the CBC report describe the quality of those cells and their ability to bring oxygen to the tissues.

What can a high white blood cell count mean?

If you think of the blood stream as a means of transportation, that is bringing defenders to a site of insult or cells that clean up dead or dying cells, then the white blood count (WBC) reflects your body’s ability to respond to an insult by defeating that insult and repairing the site of damage. What kind of damage? All kinds from a bruise to infections, auto accidents or simple daily wear and tear.

Because these cells are moving around the body searching for potential injuries, the white cell count will vary throughout the day. For example, if you run up a flight of stairs to get to your phlebotomy on time, your white blood cells will be increased. At night, when you are nodding off in your chair while watching TV, your white cell count will be lower.

So what does it mean if your lab test results show an increased white blood cell count? It is an indication that your body is in a defensive state. When your healthcare provider looks closer at your laboratory test results, the types of white blood cells are indicated and they provide clues about the cause of the increase. which include:

• Neutrophils, the most numerous in the peripheral blood, help to fight against fungi, bacteria, and other foreign invaders. They also work with monocytes in repair and healing.
• Lymphocytes, the second most numerous, are your immune system. They defend against viruses and other foreign insults that require antibody formation and memory. It is composed of cells which remain in the tissues and those which circulate in the blood stream. The cells of the blood stream include T cells which recognize the foreign insults including malignancies and direct the actions of the system, B cells which make antibodies, and natural killer cells which can kill or destroy those foreign insults.
• Monocytes, which are the primary cell for the repair of wear and tear daily turn over of cells and will fight infections with a clean-up action of cells that are damaged.
• Eosinophils, which play a crucial role with the immune system by participating in allergic reactions, defense against parasites, and releasing their cell contents to work in the inflammation process
• Basophils, which fight invaders with allergic responses

How these cells increase or decrease tells the provider about the type of cell defence being used and narrows the potential causes down.

What can a platelet count mean?

Platelets are not really cells, they are pieces of a much larger and flake off from their “mother” cell. You can think of them as small cotton scraps. If you get a small break in the wall of a blood vessel, platelets collect in that area and clump together to form a platelet plug and stop the blood loss. Larger breaks in the blood stream wall requires both platelets and a complex set of proteins to make a blood clot and stop the bleeding.

Decreased platelet counts suggest that you might not have enough platelets to form that first platelet plug or participate in the creation of a blood clot while too many platelets could suggest that it is too easy for your body to make unnecessary or larger than warranted blood clots.

What does a urinalysis test for?

A urinalysis is a test that checks a sample of your urine. It helps your healthcare provider find early signs of medical conditions that can affect your kidneys and other parts of your body.

This test looks for components of urine such as:

• Bacteria or white blood cells, which may suggest an infection
• Protein, glucose (sugar), or ketones, which can point to conditions like diabetes or kidney problems
• Red blood cells, which may indicate bleeding in the urinary tract
• Abnormal cells, bilirubin or hCG, which can provide clues about liver health, pregnancy, or certain types of cancer
• Crystals, which may signal kidney stones
• Your body’s water balance, acidity (pH), and electrolyte levels

A urinalysis is used to detect a wide range of conditions, ranging from overhydration/dehydration, to kidney and bladder diseases to more serious conditions such cancers.

What does protein or blood in my urine mean?

Finding protein or blood in your urine can be a sign of a temporary issue or a more serious medical condition.

Protein in the urine may be linked to inflammation in the body or possible kidney damage.

Blood in the urine (which may appear pink, red, or brown) can have many possible causes. Some are minor and temporary, while others may require more attention. These causes include:

• Kidney stones
• Urinary tract infections (UTIs)
• Contamination from menstrual fluid
• Endometriosis
• Kidney disease
• Bladder or prostate cancer
• Injury to the kidney
• A class of anemia called hemolysis, which will cause the red blood cells to die faster than they should
• Side effects of certain medications

If blood or protein is found in your urine in a urinalysis, your healthcare provider may recommend further testing to understand the cause and determine the right treatment, if needed.

What is a TSH level?

TSH stands for thyroid-stimulating hormone, a hormone that plays an important role in how your thyroid gland works. Your thyroid helps control your metabolism—the process your body uses to turn food into energy.

If you or your healthcare provider are concerned about your thyroid health, a TSH test is often the first step. It helps check whether your thyroid is working properly.

An abnormal TSH level may be a sign of:

• Hypothyroidism (an underactive thyroid)
• Hyperthyroidism (an overactive thyroid)
• Autoimmune thyroid conditions, such as Hashimoto’s or Graves’ disease Other thyroid-related issues
• Pituitary gland

What range is considered normal TSH levels can vary slightly depending on the lab, but they generally fall between 0.5 and 5.0 mIU/L.

If you’re experiencing symptoms like fatigue, weight changes, mood swings, or changes in heart rate, talk to your healthcare provider about whether a TSH test might be right for you.

How are T3, T4, and TSH levels interpreted?

TSH (thyroid-stimulating hormone), free T3 (triiodothyronine), and free T4 (thyroxine) are the three main thyroid hormones that healthcare providers order to aid in deciphering thyroid issues or other health issues. Some HCPs may order lab test results for reverse T3, but this is no longer commonly used. Your combination of TSH levels and free T4 levels will help your healthcare provider determine the cause of your symptoms. The following table shows how thyroid

What does bilirubin indicate in liver tests?

• Indirect bilirubin or unconjugated bilirubin that hasn’t been processed in the liver
• Direct bilirubin or conjugated bilirubin that has been processed in the liver

If you have elevated levels of direct bilirubin, this is more concerning since it indicates that there’s an issue with liver function or that there’s a blockage somewhere in the bile ducts.

What are ALT and AST, and why are they elevated?

If your lab test results show elevated ALT (alanine aminotransferase) levels, it’s typically a signal that some type of injury of the cells in the liver has occurred, which elevates the ALT enzymes. Elevated ALT can indicate liver damage or liver disease, and ALT tests are commonly part of a battery of tests called a liver function panel, which also includes ALP, AST, bilirubin, albumin and total protein, GGT, prothrombin time (PT), and L-lactate hydrogenase (LD).

ALT tests may be ordered to help diagnose a range of conditions including:

• Hepatitis A, hepatitis B, and hepatitis C
• Cirrhosis, or scarring, of the liver
• Infectious mononucleosis, commonly known as mono
• Inflammation of the liver
• Alcoholic liver disease
• Metabolic dysfunction disorders, such as MASLD and MASH

If your lab test results show elevated AST (aspartate transaminase) levels, it could be an indication of liver disease, liver damage, or muscle damage. AST is an enzyme that naturally occurs in red blood cells and aids the body in the breakdown of amino acids. An AST test is typically ordered as part of liver function tests or a comprehensive metabolic panel, and elevated AST levels can help to gauge the health of your liver. Your healthcare provider may order an AST test if they have concerns about one of the following symptoms or conditions:

• Fatigue, dark urine, stomach pain, or jaundiced (yellow) eyes or skin
• Unexplained muscle weakness or muscle pain
• Liver disease
• Long-term obesity or diabetes
• Liver disease symptoms during pregnancy

What is the difference between IgG and IgM antibodies?

If you’re curious about the difference between IgG antibodies and IgM antibodies on your lab test results, there are some key distinctions. IgM antibodies normally appear in the body before IgG antibodies and are found in your blood and lymph system. IgM antibodies play a primary role in immune regulation and serve as the first line of defense in the body. Among the five types of antibodies in the body, immunoglobulins (IgG) comprise about 70 percent to 75 percent of the antibodies in your body. IgG antibodies function to protect you from bacterial infections and viral infections, and IgG antibodies are primarily found in tissue fluids and blood fluids.

What lab tests should be repeated regularly?

Although there isn’t a list of lab tests that should be repeated regularly, many healthcare professionals will order a complete blood count (CBC), urinalysis, and chemistry panel for their patients. For cholesterol level lab test results, a lipid panel is another test that’s commonly ordered to help in monitoring your health. If you are experiencing symptoms that are bothering you, make sure to discuss them with your doctor and ask if there are lab tests that may help in diagnosing your health issue.

Lab tests are essential pieces of the puzzle that create the picture of your health and journey to wellness. If you have questions or concerns about lab tests that you’ve received or tests that might be helpful in discovering the cause of bothersome symptoms, make sure to discuss potential tests with your doctor. Diagnostic equity is within reach, and getting answers to common lab test questions takes you one step closer to your health goals.

Please note: The reference ranges mentioned in this article are examples only. Each laboratory uses different testing methods and equipment, which means reference ranges can vary. For an accurate interpretation of your clinical laboratory results, always refer to the specific range provided on your report by the lab that performed your analysis.

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Mayo Clinic. Blood in urine (hematuria). Retrieved from https://www.mayoclinic.org/diseases-conditions/blood-in-urine/symptoms-causes/syc-20353432
UCLA Health. Normal Thyroid Hormone Levels. Retrieved from https://www.uclahealth.org/medical-services/surgery/endocrine-surgery/conditions-treated/thyroid/normal-thyroid-hormone-levels
Mayo Clinic. Alanine aminotransferase (ALT) blood test. Retrieved from https://www.mayoclinic.org/tests-procedures/alanine-aminotransferase-alt-test/about/pac-20582729
Mayo Clinic. Aspartate aminotransferase (ALT) blood test. Retrieved from https://www.mayoclinic.org/tests-procedures/aspartate-aminotransferase-ast-test/about/pac-20583406
Seed, S., Hoffman, M. Annual Physical Examinations. WebMD. Retrieved from https://www.webmd.com/a-to-z-guides/annual-physical-examinations

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