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  • Writer's pictureDr. Thomas Bailey, MD

Common blood tests, and what they tell about your health.

When you see your doctor, chances are likely that at some point you will need bloodwork to evaluate your health.  There are many different tests that can be done based on your situation, but certain tests are done more routinely than others.  These tests often give a broad overview of your health and are usual in detecting conditions that may be making you ill or that may be a sign of developing health problems.  In this blog, we will look at these tests and generally what they reveal.


The first is known as the complete blood count, or CBC.  This test panel shows the numbers of the different types of blood cells your body produces.  It includes the following:

·        White blood cells-the cells that fight infection in your body.

·        Red blood cells-the cells that carry oxygen in your body.

·        Platelets-the cells that clot your blood.

In addition, the CBC may also be paired with a test called the differential, which represents a breakdown of the different types of white blood cells your body produces.  This includes neutrophils, lymphocytes, basophils and eosinophils.  Hemoglobin (the protein that contains iron and facilitates the carrying of oxygen in your red blood cells) and hematocrit (the ratio of red blood cells in your blood) are also included as part of the CBC.

High levels of white cells can be seen with infection, body inflammation, or even blood cancers (leukemias).  Looking at the differential may give your doctor a clue as to what may be the cause of increased white blood cells.  For example, high numbers of neutrophils may be a sign of a bacterial infection.  High eosinophils may be seen with parasite infections or allergic reactions.  Low levels of white cells may be a sign that your body is having a problem producing blood, which may result from many different illnesses.

Low levels of hemoglobin and hematocrit are seen with anemia (low blood).  This can be the result of several different health issues, including bleeding problems (for example bleeding ulcers or heavy menstrual bleeding), medication side effect or dietary deficiencies of certain vitamins.  High levels of hemoglobin and hematocrit can from conditions that require your body to have increased oxygen capacity.  This can be the result of smoking or heart and lung disease.  In addition, dehydration will concentrate the blood, and cause the hemoglobin and hematocrit to be higher than normal.


Another common blood test is the complete metabolic panel, or CMP.  This panel typically includes the following tests:

·        Sodium, potassium, and chloride, known as the electrolytes, which conduct electrical charges in the body that allow muscles to contract and to cause important chemical reactions necessary for body function.

·        BUN and creatinine, which is a measure of your kidney function.

·        Blood sugar

·        Calcium

·        AST, ALT, and alkaline phosphatase (known as the liver function test, or LFTs) which are measures of liver function.


A similar test is the basic metabolic panel, or BMP, which is the same as the CMP but typically excludes the liver function tests, or LFTs.


The thyroid is a gland in the body located at the base of your neck which helps to regulate the body’s metabolism.   An underactive thyroid is a common medical problem for many.  The thyroid stimulating hormone (TSH) blood test measures the signal that comes from your brain which tells your thyroid to work and is the most common way of measuring your thyroid function.  When your thyroid is underactive, the brain will release more TSH to try to “wake up” your thyroid and make it work harder.  Thus, a high level of TSH is usually an indicator that your thyroid is underactive and not working like it should.  When the thyroid is overworking, this will cause the brain to try to “slow down” the thyroid and so the TSH will be low.


Cholesterol blood tests are often checked for patients beginning at age 40.  Finding and treating high cholesterol is important in reducing health problems such as stroke and heart disease.  The cholesterol panel of tests usually includes the following:

·        Total cholesterol levels

·        LDL cholesterol, referred to as the “bad cholesterol” which may promote accumulation of cholesterol in your blood vessels and cause blockage over time.

·        HDL cholesterol, often called the “good cholesterol” as it helps to remove other forms of cholesterol from your blood and may reduce the chance of blockages.

·        Triglycerides, which are the most common form of fat in the blood stream and are highly dependent on the amount of fat consumed in your diet.


Just from these tests alone, your doctor can tell a great deal about your health and are likely the first steps to uncovering the cause of a variety of health problems.  I hope that this helps in your understanding of some of the basic blood tests that may be ordered for your care.  As always, discuss any questions you have with your doctor.

A patient having his blood drawn for testing by a doctor


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