Understanding blood tests and what those elements and numbers on your results mean.
Have you ever felt confused when reviewing your blood test results? You’re not alone. Even medical professionals needed time and training to fully understand what the results really mean.
For starters, there are different types of blood tests. But regardless of the panel or type of test, the results inevitably come back with technical terms and numerical results in various formats.
What do these symbols and numbers mean? What do these results say about your overall health? Are negative results a good or bad thing?
Why Do We Need Blood Tests?
Blood tests are diagnostic tools. They help healthcare providers and medical professionals diagnose your health or illness, by analyzing the chemical content of and markers in your blood.
Physicians don’t always order blood tests. Often, the physical exam your doctor or caregiver conducts by checking your breathing, heart rate, blood pressure, eyes, ears and throat are enough to determine your current health.
But there are times when a blood test isn’t just warranted. It may be critically necessary, especially if you have a serious infection or disease.
The primary reasons blood tests are conducted include the following:
- Precision. Blood tests can provide a more precise measurement of your body’s health in addition to a standard physical examination.
- For example, measuring glucose levels in patients who have diabetes allows their caregiver to monitor and administer medications. They can also recommend additional lifestyle changes when they see fluctuations in sugar levels.
- Organ health. Blood tests allows you and your physician to accurately assess how well key organs like your liver and kidneys are operating.
- For example, people diagnosed with hepatitis can lead normal lives through the periodic monitoring of their liver function through blood tests.
- Infections. Blood-borne infections, such as meningitis (inflammation of the brain and spine linings), osteomyelitis (bone infection), sepsis (the body’s extreme response to an infection), and parasitic diseases, are confirmed by a blood test.
- Blood tests can also provide a confirmation or measurement of other diseases through blood-borne markers and residue of those diseases, like CD4 cells in patients diagnosed with HIV.
- Chronic illness. Chronic diseases like diabetes, kidney failure and coronary artery disease can be diagnosed, monitored and managed through the use of blood or urine tests.
- Doctors often evaluate your kidney functions by first using a urine strip to measure its protein levels: the higher the protein level, the more likely something abnormal is going on, which would then require further blood testing.
- Pre-treatment. Prior to surgery and some medications, a blood tests may be needed to ensure that the patient’s body and organs are strong enough for the treatment.
- For instance, patients taking Roaccutane (vitamin A derivative) for their acne typically have to undergo lipid and liver tests. They may also have to take a pregnancy test, to avoid any potential fetal deformities caused by vitamin A.
- Drug dosage and effectiveness. In some instance, like osteomyelitis and cancers, a specific level of medications in the blood has to achieved to eradicate the infection or the cancerous cells.
- This can also apply to sepsis and other infections that occur in difficult-to-examine areas of the body, such joints and the central nervous system.
Types of Blood Tests
When you or your physician orders a blood test, there are an array of tests from which to choose. The following lab procedures are the most common types of blood tests conducted today:
- Complete Blood Count (CBC). This gives information about the cells in your blood, such as the cell count for each blood cell type and the concentrations of hemoglobin (the protein molecule in your blood cells that carry and transport oxygen).
- Basic Metabolic Panel (BMP). This blood chemistry test measures the levels of certain chemicals in your blood. It confirms how well your organs are working and can help detect abnormalities. Blood chemistry tests may also be called chemistry panels.
- Comprehensive Metabolic Panel (CMP). The CMP is a more expanded blood chemistry test than the BMP.
- Blood enzyme test. When cells are damaged, enzymes are released into your blood stream. Blood enzyme tests help to detect the presence of certain diseases. For example, the enzyme troponin is often released into the blood stream after a heart attack. Physicians will often run a blood enzyme test that looks for the presence of troponin, to determine whether a patient has ahad a heart attack.
- Blood tests to assess heart disease risk. Since the amount of lipids or fats have a direct impact on your heart functions, this type of blood tests may be necessary to measure and monitor in high-risk patients.
More About the CBC Test
The CBC test is the most commonly requested lab test and is often included in any routine checkup. It can detect blood diseases and disorders, such as anemia (lack of healthy red blood cells or hemoglobin), infections, clotting problems, blood cancers, and immune disorders.
This test measures many parts of your blood.
- Red blood cells. Red blood cells contain hemoglobin that carries oxygen from your lungs to the rest of your body. Abnormal red blood cell levels may be a sign of anemia, dehydration, bleeding, or other disorders.
- The normal range for men is 4.5 million to 5.9 million cells per microliter (cells/mcL); for women it’s 4.1 million to 5.1 million cells/mcL.
- White blood cells. White blood cells are an important part of your immune system, which is your body’s first line of defense for fighting infections and diseases. Abnormal white blood cell levels may be a sign of infection, blood cancer or an immune system disorder.
- The normal range is 4,500 to 10,000 cells per microliter (cells/mcL).
- Platelets. Blood platelets are blood cell fragments that help your blood clot. They stick together like glue to seal cuts or breaks on blood vessel walls, thereby allowing your body to stop minor bleeding. Abnormal platelet levels may be a sign of a bleeding disorder (insufficient clotting) or a thrombotic disorder (too much clotting).
- The normal range is 150,000 to 450,000 platelets per microliter (mcL).
- Hemoglobin. The hemoglobin is an iron-rich protein in your red blood cells that carries oxygen around your body. Abnormal hemoglobin levels may be a sign of anemia or other blood disorders.
- The normal range for men is 14 to 17.5 grams per deciliter (gm/dL)
- For women, the normal range is 12.3 to 15.3 gm/dL.
- HBA1C. If you have diabetes, excess glucose in your blood can attach to hemoglobin and raise the level of hemoglobin A1C (HBA1C). Your red blood cells have a life span of 120 days, and HBA1C reflects the exposure of hemoglobin to glucose in your red blood cells, hence why this test can provide you with a 3-month (120 day) retrospective view of your glucose levels. No fasting is required for this test.
- The normal range for HBA1C is less than 5.7%.
- You are considered pre-diabetic if your HBA1C level is between 5.7% and 6.4%.
- A level of 6.5% or higher means diabetes.
- Hematocrit. Hematocrit is a measurement of how much space red blood cells take up in your blood. Think of it as the amount of tea between the bubbles in your Boba tea.
- A high hematocrit level might mean you’re dehydrated. A low hematocrit level might mean you have anemia.
- The normal range for men is between 41.5% and 50.4%.
- For women the range is between 36.9% and 44.6%.
- Mean corpuscular volume (MCV). The MCV is a measure of the average size of your red blood cells. Abnormal MCV levels may be a sign of anemia or thalassemia (abnormal red blood cell shapes).
- A normal-range MCV score is 80 to 96.
More About the BMP
A blood chemistry test is actually a group of tests that measures different chemicals in the blood.
These tests usually are done on the fluid part of blood (the clear part known as plasma). The tests can give doctors information about your muscles (including your heart), bones, and organs, such as the kidneys and liver.
It includes blood glucose, calcium, and electrolyte tests, as well as blood tests that measure the kidney functions. Some of these tests require you to fast before the test (usually 12 hours), and others don’t. Your doctor will tell you how to prepare for the tests you are taking.
The normal range is between 64 and 100 milligrams per deciliter (mg/dL) or 3.55 to 5.55 millimoles per liter (mmol/L).
Glucose is a type of sugar that your body uses for energy. Depending on how well your cells consume glucose, abnormal levels may be a sign of diabetes.
For some blood glucose tests, you have to fast before your blood is drawn (12 hours prior).
The calcium concentration is normally between 8.5 and 10.2 milligrams per deciliter (mg/dL).
Calcium is an important mineral in the body. Abnormal calcium levels in the blood may be a sign of kidney problems, bone disease, thyroid disease, cancer, malnutrition, or other disorders.
Called electrolytes because they actually have an electrical charge, these are minerals that help maintain fluid levels and acid-base balance in the body. Common electrolytes examined during a blood test include:
- Sodium. Normal blood sodium level is 135 – 145 milliequivalents per liter (mEq/L)
- Potassium. Normal blood potassium level is 3.5 – 5.0 (mEq/L)
- Bicarbonate. Normal serum range for bicarbonate is 22-30 millimoles per liter (mmol/L)
- Chloride. Normal serum range for chloride is 98 – 108 mmol/L
Abnormal electrolyte levels may be a sign of dehydration, kidney disease, liver disease, heart failure, high blood pressure, or other disorders.
Blood tests for kidney functions measure levels of…
- Blood urea nitrogen (BUN). Normal BUN level is 7-20 mg/dL
- Creatinine. Normal creatinine clearance is 88-128 millileter per minute (mL/min) for women and 97-137 mL/min for men
Both of these compounds are waste products that your kidneys are supposed filter out of the body. Abnormal BUN and creatinine levels may be signs of a kidney disease or disorder.
More About the CMP
The comprehensive metabolic panel measures all the factors mentioned in the above BMP. In addition, the CMP includes two protein tests – for albumin and total protein – as well as other liver function tests:
- Albumin. The normal range for albumin is 3.4 to 5.4 grams per deciliter (g/dL). Albumin is produced by your liver, and it helps keep fluid in your bloodstream, so it doesn’t leak into other tissues.
- Total protein. The normal range is 6 to 8 g/dL. It is used for liver and kidney functionality, and levels can spike during infections or malignancies.
- ALP (alkaline phosphatase). The normal range is 44 to 147 international unit per deciliter (IU/L). The ALP examines your nutrition and liver functions. Abnormal values might may sign liver, gallbladder, or bone disease.
- ALT (alanine aminotransferase). The normal range is 20-60 IU/L. The ALT examines your liver functions and is increased if the liver is damaged.
- AST (aspartate aminotransferase). The normal range is 10 to 35 IU/L. Th AST looks at kidney and liver functions. It is also used to measure the effect of alcohol on the liver.
- Bilirubin. The normal range is 0.1 to 1.2 mg/dL (1.71 to 20.5 µmol/L). Bilirubin helps diagnose health conditions like jaundice, anemia, and liver disease.
Blood Tests to Assess Heart Disease Risk
A lipoprotein panel is a blood test that can help show whether you’re at risk for coronary heart disease (CHD). This test looks at substances in your blood that carry cholesterol, which, if abnormal, can cause cardiovascular disorders.
A lipoprotein panel gives information about your cholesterol and fat levels:
- Total cholesterol. This measure both your LDL and HDL combined and should be maintained under 200 mg/dL to lower the risk of cardiovascular diseases.
- LDL “bad” cholesterol. This is the main source of cholesterol buildup and blockages in the arteries and should be maintained under 100 mg/dL.
- HDL “good” cholesterol. This type of cholesterol helps decrease blockages in the arteries and should be maintained higher in the 40-59 mg/dL range.
- Triglycerides. Is the other bad type of fat in your blood and should be maintained under 150 mg/dL.
Most people will need to fast for 9 to 12 hours before a lipoprotein panel.
More About Blood Enzyme Tests
Enzymes are chemicals that help control chemical reactions in your body. There are many blood enzyme tests. Here, we’ll focus on enzyme tests used to check for heart attack:
- Troponin. Troponin is considered abnormal of it exceeds the concentration of 0.4 (ng/ml). It is a muscle protein that helps your muscles contract. When muscle or heart cells are injured, troponin leaks out of cardiac tissue, and its levels in your blood rise. For example, blood levels of troponin rise when you have a heart attack. For this reason, doctors often order troponin tests when patients have chest pain or other heart attack signs and symptoms.
- Creatinine Kinase (CK). The normal range for CK is 22 to 198 U/L. A blood product called CK-MB is released when the heart muscle is damaged. High levels of CK-MB in the blood can mean that you’ve had a heart attack.
How Long Does it Take to Get Your Blood Test Results?
The short answer is that “it depends. Sometimes, results are available instantly, within minutes of performing the test (e.g. finger prick tests for glucose, or a urine test strip). Other tests can take days or weeks to obtain blood test results (e.g. STI tests, electrolytes).
Whether normal or abnormal, physicians and medical professionals are obligated to contact you when your results are ready. Your doctor should be available to answer your inquiries over the phone or schedule you for a follow up in case of an abnormality.
Sometimes, results are available instantly, within minutes of performing the test.. Other tests can take days or weeks.
The time between the blood sample being taken and your doctor receiving the results can vary based on the category:
- Complete blood count (CBC). This test measures several cell types (as we mentioned above). CBC results are usually available for your provider within 24 hours.
- Blood chemistry tests (Basic and Comprehensive metabolic panel). You may be asked to fast for a certain period of time before having your blood drawn. These results are also typically sent to your doctor within 24 hours.
- Blood Enzymes. Since Troponin and CK are usually ordered after a suspected heart attack, it is essential to receive the results as fast as possible. Luckily, with current lab advancements, these results can be produced in less than an hour.
- Lipid panel. Lipids are usually measured on routine visits, and your doctor should receive results from the lab within 24 hours as well.
What if the Lab Tests are Abnormal?
When you receive your lab result printout, you will notice each component on the left of the page, with a corresponding number next to it which is your result.
Usually the normal range is printed out as a reference. For instance, if your blood work includes potassium levels in the blood, your lab may list the normal range for potassium as 3.7 to 5.2 milliequivalents per liter (mEq/L). If your result falls within that range, then you can rest assured that your potassium level is normal.
What if your results are outside of the normal range? Our advice: FOFO, find out before you freak out.
Don’t jump to conclusions. But do contact your physician to schedule an appointment. Some tests can fluctuate from the normal range due to various reasons that are not pathological. These reasons can include:
- Side effects from medications
- Recently treated infections
- Faulty lab procedures
- Strenuous exercising
It is also important to look at your entire picture of health to interpret a blood test. Numbers on paper cannot paint a story, but you do. Taking your lab results into consideration along with your general health track record, your habits and mental status is imperative.
There is no substitute to seeing your physician to help you better understand your lab results. But knowing what each test means can help you take full charge of your health. Understanding what your doctor is telling you leads to formulating more informed questions, and ultimately allows you to make the right decisions about your health.