Many times, your healthcare provider will perform lab testing to try to figure out what is going on in your body or to prevent chronic diseases from progressing. What do these lab tests really measure?
What could they mean if they are too high or too low?
Let’s start with the “Hemogram”. The hemogram measures hemoglobin, red blood cell count, hematocrit (packed cell volume), MCV (mean corpuscular volume), MCH (mean cell hemoglobin), MCHC (mean cell hemoglobin concentration), total white blood cell count, differential count, and platelet count.
So, what do these numbers tell us? In a nutshell, these numbers can test for anemia, but there are other reasons why some of these levels will be too high or too low.
Hemoglobin is a protein in red blood cells that carries oxygen throughout the body and to the cells so they can perform their functions. If our body is deficient in iron, vitamin B12, or folate, the proteins in the red blood cells will not be able to carry as much oxygen to our cells and our energy levels will decrease (a tell-tale sign of anemia). Other causes of anemia can include active or chronic bleeding conditions including stomach ulcers, genetic causes like sickle cell anemia, chronic medical conditions like liver disease, kidney disease, or cancer, and certain medications can lead to anemia (chemotherapy drugs, antibiotics, antidepressants, and pain relievers).
The red blood cell count is just like it says – it counts the number of mature red blood cells in the sample. Hematocrit is the packed volume of red blood cells and certain medications can change these values. Clozapine, carvedilol, atropine, and cefoxitin can increase hematocrit levels. Ofloxacin, phenytoin, theophylline, enalapril, losartan, and dipyrone can decrease hematocrit levels.
The red blood cell indices (MCV, MCH, MCHC) give clues to the size of the red blood cells and the concentration of hemoglobin in each red blood cell. This can give more information about what could be causing the anemia.
White blood cells are the immune cells that fight invaders and infections in our body. When doctors check the white blood cell counts and differentials, they are looking for signs of acute infections or inflammatory disorders.
Neutrophils can decrease if a patient is on chemotherapy or radiation treatments, certain infections like typhoid, measles, or rubella, and systemic lupus erythematosus. High neutrophil levels usually indicate an acute infection.
Basophils can be lower in pregnancy and ovulation, as well as hyperthyroid disorders. Basophils are increased by certain cancers like chronic myelocytic leukemia, polycythemia vera, and Hodgkin’s disease. High levels can also be seen in ulcerative colitis, an inflammatory disease of the gut.
Eosinophil levels can be decreased during stressful situations like surgery and also with Cushing’s disease. They can be increased with allergies, infections caused by parasites, skin diseases, and some cancers.
Lymphocytes can increase with infections like tuberculosis, syphilis, and pertussis, and autoimmune diseases like ulcerative colitis. Lymphocyte levels will be low in congestive heart failure, renal failure, and with corticosteroid therapy.
Monocytes are usually increased due to infections like tuberculosis or bacterial endocarditis, or autoimmune diseases like rheumatoid arthritis or systemic lupus erythematosus.
Platelet counts help healthcare providers check if you have bleeding or clotting disorders. Some nutrient deficiencies like low levels of iron, folate, and B12 can decrease platelet counts. Some medications like buspirone, azathioprine, albendazole, and amiodarone can also decrease platelet counts and increase your risk for bleeding. We also have certain blood thinning medications specific for this purpose.
Next, let’s talk about blood sugar and hemoglobin A1c, which is used to diagnose diabetes. Usually, doctors will test a fasting blood sugar level, which means that the person has not had anything except water for the 8 hours before the test.
A normal fasting range is 70-99, prediabetes is 100-125, and diabetes is greater than 126 mg/dL. However, any random blood sugar check greater than 200 mg/dL is suggestive for diabetes. More tests would need to be done at different times to make a definitive diagnosis.
Another blood test that is used to diagnose diabetes is the hemoglobin A1c test. A certain amount of glucose is always attached to the hemoglobin in red blood cells. Since a red blood cell is usually present for 120 days, HbA1c gives an estimate of the average blood sugar over the last 3 months. Normal levels are less than 5.7%, prediabetes is 5.7 – 6.4% and diabetes is greater than 6.5%. Caution should be used when using HbA1c as a diagnostic tool. If the patient has a form of anemia (from iron, B12 or folate deficiency), results of a HbA1c test would be skewed. It is best to fix the anemia and retest HbA1c again for more accurate results.
Thyroid function tests are lab tests used to determine if the thyroid gland is functioning properly. The thyroid gland is important for regulating our metabolism and many other functions in our body. The pituitary gland secretes a hormone called TSH, which is the thyroid stimulating hormone. The thyroid gland secretes T3 (triiodothyronine) and T4 (thyroxine). If T3 and T4 levels are low, the body sends out more TSH to stimulate the thyroid to make more.
Increased T4 levels may be due to hyperthyroidism (or an over-active thyroid gland), hepatitis, or acute thyroiditis. Decreased T4 levels can be a sign of malnutrition, cirrhosis, hypothyroid (low-thyroid activity), or chronic thyroiditis. Sometimes they will measure a free T4 level to understand more about how the thyroid gland is functioning. Some medications can affect T4 levels like hormone therapies (testosterone, estrogen, birth control), some cancer medications, and steroids. TSH levels are measured to determine if more or less T3 and T4 are needed by the body.
To gain more of an understanding for why the thyroid gland may not be functioning well, a thyroid peroxidase antibody test will sometimes be performed. This can show if there are specific antibodies in the blood working against the thyroid. If antibodies are present, this could be due to an autoimmune disease like Graves’ disease or Hashimoto’s thyroiditis.
Liver function is measured by checking serum bilirubin, albumin, and globulin. Bilirubin is the breakdown of hemoglobin and elevated levels lead to the tell-tale sign of jaundice, yellow skin and eyes. Albumin is a protein found in the blood that helps to transport other proteins and hormones. High levels of albumin are a sign of dehydration. Low levels of albumin can be a sign of liver diseases, kidney diseases, malnutrition, or from burn injuries. Globulin is another protein in the blood that helps with hemoglobin binding and transport, as well as some immune functions.
Albumin and globulin are usually found in a specific ratio of 60% albumin and 40% globulin. Changes in this ratio can be seen in chronic inflammatory diseases, autoimmune disorders (rheumatoid arthritis), and multiple myeloma.
Some other liver function tests include alkaline phosphatase, aspartate aminotransferase, alanine transaminase, and gamma glutaryl transferase.
Alkaline phosphatase is an enzyme found in the liver, bones, and intestines. It has many metabolic functions and appears to play a role in the mineralization of bones. Increased levels of alkaline phosphatase can be a sign of liver diseases, bone disorders, and certain cancers (like lymphoma or leukemia). Decreased levels may be signs of Wilson’s disease, too much phosphate in the blood, or thyroid disorders. Certain blood disorders like pernicious anemia, aplastic anemia and chronic myelogenous leukemia can also cause decreased levels of alkaline phosphatase.
Aspartate aminotransferase (AST) is an enzyme found in the liver, heart, kidney, brain, muscles, and red blood cells. Increased levels of AST can be a sign of damage to the liver, heart, or kidneys. Decreased AST can be seen in congested liver or in patients with high cholesterol levels.
Alanine transaminase (ALT) is an enzyme that is specific for liver function, although ALT is also found in the kidney. AST and ALT levels are used together in a ratio to determine liver function. An elevated ALT level points to liver disfunction, such as fatty liver or cirrhosis.
Gamma glutaryl transferase (GGT) is found in the liver, kidney, and pancreas. Increased levels of GGT are associated with liver diseases (cirrhosis, hepatitis, alcoholic liver disease, or liver cancer), prostate, breast, and lung cancers, pancreatitis, and systemic lupus erythematosus. GTT levels may be lower in hyperthyroidism, hypothalamic dysfunction, or low magnesium levels.
Next, let’s talk about kidney function tests. The first is the blood urea nitrogen (BUN). Typically, our body will break down unused proteins and amino acids into urea and carbon dioxide. We breathe away the carbon dioxide through the lungs, but the urea is removed by the kidneys. If the kidneys are not functioning properly, the amount of urea in the blood will increase. So, a high BUN can point to a dysfunction in our kidneys. Increased BUN can also be caused by low fluid intake, exercise, high protein intake, certain medications, heart failure or intestinal bleeding. Low levels can be due to malnutrition, liver damage, malabsorption, or a low nitrogen diet.
Serum creatinine (SCr) is another test for kidney function. Creatinine is a waste product when creatine (found in muscle tissue) breaks down. This happens at a constant rate and is filtered out of the blood stream by the kidneys, so it is a measurement of how well the kidneys are functioning. Levels increase as kidney function decreases. Certain medications that can block kidney function can also raise SCr levels. Losing muscle mass can also increase SCr levels. Low SCr levels can happen in pregnancy, inadequate protein in the diet, or liver disease.
The BUN:Creatinine ratio is used to assess kidney function. A BUN:SCr ratio >20:1 is usually related to dehydration or poor blood flow; <10:1 can show kidney damage.
There are many other labs that might be performed such as checking certain electrolyte levels (sodium, potassium, calcium, etc.). I’m not going to get into those, today, but I hope this has been a helpful post about some of these common lab tests that are performed. I will write a future post about the lab tests that Functional Medicine providers offer.
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