The most important thing that anyone can do when feeling ill is to see a caring physician. Our bodies change constantly, and one of the most valuable tools that the physician uses to assess your health is the laboratory blood test. Blood tests take an internal and dynamic ‘snapshot’ of you, at the time of the test. Each drop teems with data, not just about your current state of health but also about what your future might hold. For example, a blood test can help doctors:
- assess your general state of health
- check if you have an infection
- see how well organs, such as the liver and kidneys, are working
- find out whether you have risk factors for heart disease
- check whether medicines you’re taking are working
- assess how well your blood is clotting
The arm is a convenient part of the body to use because it can be easily uncovered. The usual place for a sample to be taken from is the inside of the elbow or wrist, either from a vein or from an artery. A few drops of blood are needed, most of the time. It is often enough to take a small drop from the tip of your finger and then squeeze the blood out for blood testing.
Blood is made up of different kinds of cells and contains other compounds, including various salts and certain proteins. The liquid portion of the tested blood is plasma and serum, which can be used in chemical tests and in other blood tests to find out how the immune system fights diseases.
Most blood tests fall within one of two categories: screening or diagnostic.
Screening blood tests are used to try to detect a disease when there is little or no evidence that a person has a suspected disease. For example, measuring cholesterol levels helps to identify one of the risks of heart disease. These screening tests are performed on people who may show no symptoms of heart disease, as a tool for the physician to detect a potentially harmful and evolving condition.
Diagnostic blood tests are utilized when a specific disease is suspected to verify the presence and the severity of that disease, including allergies, HIV, AIDS, Hepatitis, cancer, etc.
Some of the most common blood test are:
Allergy Blood Testing
Blood Tests for Autoimmune Diseases
Blood Diseases Testing
Cancer Detection Blood Testing
Blood Cholesterol Test
Diabetes Blood Tests
DNA, Paternity and Genetic Testing
Blood Tests for Drug Screening
Environmental Toxin Blood Testing
Fitness, Nutrition and Anti-Aging
Gastrointestinal Diseases Revealed by Blood Tests
Blood Testing for Heart Health
Hormones and Metabolism
Infectious Disease Blood Tests
Kidney Disease Blood Test
Liver Diseases Blood Testing
Sexually Transmitted Diseases (STD’s) Blood Tests
Thyroid Disease Blood Tests
The healthcare professional who arranges your blood test will tell you whether there are any specific instructions you need to follow before your test. Many blood tests don’t require any special preparation and take only a few minutes. Other blood tests require fasting (not eating any food) for 8 to 12 hours before the test. For example, depending on the type of blood test, you may be asked to:
- avoid eating or drinking anything, apart from water (fasting) for up to 12 hours
- stop taking a certain medication
Some of the most common blood tests are:
- A complete blood count (CBC)
- Blood chemistry tests
- Blood enzyme tests
- Blood tests to assess heart disease risk
Complete Blood Count
The CBC is one of the most common blood tests. It’s often done as part of a routine checkup.
The CBC can help detect blood diseases and disorders, such as anemia, infections, clotting problems, blood cancers, and immune system disorders.
Red Blood Cells
Red blood cells carry oxygen from your lungs to the rest of your body. Abnormal red blood cell levels may be a sign of anemia, dehydration (too little fluid in the body), bleeding, or another disorder.
White Blood Cells
White blood cells are part of your immune system, which fights infections and diseases. Abnormal white blood cell levels may be a sign of infection, blood cancer, or an immune system disorder.
Platelets (PLATE-lets) are blood cell fragments that help your blood clot. They stick together to seal cuts or breaks on blood vessel walls and stop bleeding.
Abnormal platelet levels may be a sign of a bleeding disorder (not enough clotting) or a thrombotic disorder (too much clotting).
Hemoglobin (HEE-muh-glow-bin) is an iron-rich protein in red blood cells that carries oxygen. Abnormal hemoglobin levels may be a sign of anemia, sickle cell anemia, thalassemia (thal-a-SE-me-ah), or other blood disorders.
Hematocrit (hee-MAT-oh-crit) is a measure of how much space red blood cells take up in your blood. A high hematocrit level might mean you’re dehydrated. A low hematocrit level might mean you have anemia.
Blood Chemistry Tests/Basic Metabolic Panel
The basic metabolic panel (BMP) is a group of tests that measure different chemicals in the blood. These tests usually are done on the fluid (plasma) part of blood. The tests can give doctors information about your muscles (including the heart), bones, and organs, such as the kidneys and liver. The BMP includes blood glucose, calcium, and electrolyte tests, as well as blood tests that measure kidney function. Some of these tests require you to fast (not eat any food) before the test, and others don’t. Your doctor will tell you how to prepare for the test(s) you’re having.
Glucose is a type of sugar that the body uses for energy. Abnormal glucose levels in your blood may be a sign of diabetes. For some blood glucose tests, you have to fast before your blood is drawn. Other blood glucose tests are done after a meal or at any time with no preparation.
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 another disorder.
Electrolytes are minerals that help maintain fluid levels and acid-base balance in the body. They include sodium, potassium, bicarbonate, and chloride. 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 function measure levels of blood urea nitrogen (BUN) and creatinine. Both of these are waste products that the kidneys filter out of the body.
Blood Enzyme Tests
Enzymes are chemicals that help control chemical reactions in your body. There are many blood enzyme tests. This section focuses on blood enzyme tests used to check for heart attack.
Troponin is a muscle protein that helps your muscles contract. When muscle or heart cells are injured, troponin leaks out, 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.
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.
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.
A lipoprotein panel gives information about your:
- Total cholesterol.
- LDL (“bad”) cholesterol. This is the main source of cholesterol buildup and blockages in the arteries. (For more information about blockages in the arteries, go to the Diseases and Conditions Index Atherosclerosis article.)
- HDL (“good”) cholesterol. This type of cholesterol helps decrease blockages in the arteries.
- Triglycerides. Triglycerides are a type of fat in your blood. Most people will need to fast for 9 to 12 hours before a lipoprotein panel.
Blood clotting tests sometimes are called a coagulation panel. These tests check proteins in your blood that affect the blood clotting process. Abnormal test results might suggest that you’re at risk of bleeding or developing clots in your blood vessels. Your doctor may recommend these tests if he thinks you have a disorder or disease related to blood clotting.
After the blood sample has been taken, it will be put into a bottle and labeled with your name and details. It will then be sent to a laboratory where it will be examined under a microscope or tested with chemicals, depending on what’s being checked. There are thousands of lab tests, and their results can mean different things. But a few general guidelines can help shed some light.
Here are a few things to look for:
Positive vs. Negative. Some lab tests answer yes-or-no questions like whether you’re pregnant or have certain kinds of infections. These results are usually written as “positive” or “negative.” In this case, positive doesn’t necessarily mean “good” and negative doesn’t necessarily mean “bad.”
- Positive: The lab found whatever your doctor was testing for. So if you had a test for strep throat, testing positive means you do have strep throat.
- Negative: The lab didn’t find whatever you were tested for. A negative result for strep throat means that the lab didn’t find any strep bacteria in the sample, so you probably don’t have it.
Reference Ranges. A lot of lab test results don’t give clear answers. Instead, they’re shown as a number — like your cholesterol levels. These numbers don’t mean anything on their own, so you have to see how yours compare to a healthy range called your “reference range” or “reference value.” You’ll see this range on the lab test results.
Remind your doctor if you take medications, be honest if you didn’t follow the instructions. With some lab tests, you’re supposed to fast (not eat), or not do certain activities, eat certain foods, or take certain drugs. If you forget and mess up, don’t worry — just tell your doctor before you do the test. It’s not a big deal to reschedule, and it’s a waste of time to get the test if the results won’t be right.
You already know that a simple blood test can tell you a lot about your health. You may be surprised at all the information a doctor can draw out of your arm or the tip of your finger. A blood test can reveal about you your “biological” age or whether you’re depressed:
— Your true age.
Compared to your “chronological age,” which is the amount of time that has elapsed since you were born, your “biological age” refers to how old your body and internal systems seem compared to other folks in your age group. So while you may be 52, your biological age may more closely resemble a healthy 48-year-old’s.
— Your risk for Alzheimer’s—10 years from now.
Your blood’s levels of a small group of proteins may indicate whether you’ll develop Alzheimer’s disease 10 years before any symptoms appear.
— Whether you’ve suffered a concussion.
Doctors have long struggled to come up with a protocol that accurately assesses whether you’ve suffered a concussion—a traumatic brain injury that, for some, may not result in any obvious symptoms in the hours or days following the event. That’s a big problem—especially for athletes—because suffering a second blow to the head too soon after a concussion can be deadly or result in long-term cognitive problems.
— Your dehydration levels.
Dehydration puts stress on your heart, increases fatigue, and can make it hard to think clearly. And roughly 20% of older adults in assisted living facilities are dehydrated—mostly because they’re simply not drinking enough fluids.
— The severity of your blues.
It can be tough for some people (and their doctors) to differentiate between healthy, happens-to-all-of-us stretches of the blues and more sinister forms of clinical depression. And for years, experts believed it really wasn’t possible to identify mood disorders using blood tests or brain scans. The blood test may help doctors prescribe more effective drugs to treat clinical depression.
— Every cold you’ve ever had
Like a goopy red medical record coursing through your veins, your blood can reveal to doctors every virus or cold you’ve ever endured. Your body develops antibodies in response to the illnesses you fend off. And those antibodies continue to kick around in your bloodstream for the remainder of your life.
If you’re visiting a doctor on the regular, he should keep you up to date on the blood tests that can help you stay healthy long-term. He’ll also be able to perform in-person screenings for issues like alcohol abuse, high blood pressure, or depression; administer vaccinations; and recommend health-promoting changes to your diet or exercise routine. In other words, blood tests alone are no panacea. Still, it’s important to know what you need and when. Here are a few of the biggies.
Blood glucose test for diabetes
If you’re overweight and have high blood pressure and a history of diabetes in your family, you’re a prime candidate for a screening test of the sugar in your blood. Doctors recommend a blood glucose test for adults between the ages of 40 and 70 who are overweight or obese. How often you need to be screened will come down to your individual risk factors.
Lipid panel for high cholesterol
Cholesterol is measured as part of a blood test called a lipid panel, which looks at types of fat in your blood. Doctors recommend that all men age 35 and older get screened, as well as women age 45 and older with an increased risk of heart disease. The exact frequency of a cholesterol test will likely depend on how healthy you are overall.
In the near future, a blood test may be able to detect early breast cancer more reliably than a mammogram; it might even alert doctors to the first signs of Alzheimer’s, making it possible to intervene before toxic changes ravage the brain. Success will mean a transformation in medicine as blood tests reveal things that have until now required invasive surgery or radiation imaging. Blood’s advantages are obvious: it’s easy to access, it’s inexpensive to test, and nearly every doctor’s office or clinic can draw a tube of it.
Get an annual check-up, and don’t skip routine bloodwork. Even if you feel that you’re healthy, it’s still a good idea to have a continuous record of standard blood markers so your doctor can look for trends. If you have some results at the high or low end of normal, ask your doctor if you should repeat the test or investigate them further.