Reviewed By: Dr. Kurt Kloss, MD
Last Reviewed Date: Sep 25, 2018
Last Modified Date: Sep 25, 2018
Published Date: Aug 29, 2017
What you should know about lab tests: Every adult, even those in perfect health, will at one time or another need a general lab test. Many of these tests are used to establish baseline numbers during regular checkups, as part of screening for specific diseases and as a way for healthcare providers to prescribe treatments.
Lipid screening, for example, is used to determine total levels of cholesterol and is recommended on a regular basis for those with a family history of high cholesterol or other risk factors. A simple blood test can also check for anemia, iron levels and potentially serious blood disorders. Concerned about diabetes, hepatitis, infection, whether or you are pregnant? A blood test can provide the answers.
Along with regular check-ups, general lab tests are designed for preventive care, offering a proactive approach to healthcare and the ability to find and treat certain diseases early when treatment is most effective.
Common Questions about General Lab Testing
What should I expect when a blood test is administered?
Most routine diagnostic lab tests require a blood sample. It’s a brief, generally painless experience (a quick sting or less discomfort level) but it often causes anxiety, especially for those who are needle-phobic or don’t like the sight of blood, especially their own.
A health professional will ask you to raise your sleeve and wrap an elastic band (tourniquet) around the upper part of your arm to apply pressure, which causes veins to swell with blood. The skin surface is cleaned with antiseptic and a small needle inserted inside the elbow or on the back of the hand. The blood is then withdrawn and collected in a vial or a syringe. When the needle is removed, the elastic band is also removed, a cotton ball placed on the puncture site and if needed, a small bandage applied to stop the bleeding.
The entire procedure generally takes less than five minutes. A skilled healthcare professional can perform a lab draw with hardly any discomfort at all, quickly and easily. If apprehension over lab testing is a major drawback for you, see tips at the end of this FAQ on how to reduce your anxiety level.
If I can afford to have only a minimum number of lab tests performed, what should they be?
That depends upon age, family history and overall health. If you are under the care of a physician, ask which tests are best for you that match your current healthcare status.
For general purposes, many healthcare providers suggest the following:
- Basic Metabolic Panel (BMP) – a set of eight tests that together can provide information about glucose (sugar) and calcium levels in the blood, how the kidneys are functioning and overall electrolyte and fluid balance.
- Comprehensive Metabolic Panel (CMP) – coupled with a Complete Blood Count (CBC) these tests analyze more than 40 basic blood parameters including:
- Cardiovascular Risk Profile – measures total cholesterol and triglycerides, along with an estimated risk for coronary heart disease (CHD).
- Liver Function – shows if the liver is functioning properly and if any inflammation is present; can monitor changes in liver function when medications are administered.
- Kidney Function – establishes current health status of the kidneys
- Blood Chemistry – measures the levels of certain electrolytes, including sodium and potassium. Typically ordered to look for signs of diabetes, kidney dysfunction or metabolic disorders.
- Complete Blood Count (CBC) – also known as CBC with Differential, this is a panel of tests often used for broad screening purposes to determine general health. It can also screen for a number of conditions and diseases, including anemia, leukemia and infection, as well as monitor treatment effectiveness. White blood cells (WBC) (fight infection), red blood cells (RBC) (transport oxygen throughout the body) and platelets (cell fragments vital for blood clotting) are all measured for normal ranges. A white blood cell differential identifies and counts the numbers and types of white blood cells present. Note: a recent blood transfusion can affect the results of a CBC.
- Serum Lipid Panel – strongly recommended starting at age 35, this test screens for the presence of high cholesterol levels which can lead to coronary heart disease; recommended at age 20 if family history or other risk factors are present.
Heart disease runs in my family so I think I’m at higher risk for a cardiovascular event. What lab tests are best for me?
Always check with your healthcare provider, but in general, if there is a strong predisposition to coronary heart disease (CHD) in your family history, consider having a: Vertical Auto Profile (VAP) or Lipoprotein Particle Profile (LPP) – two newer forms of cholesterol tests that measure many different elements in the blood, including patterns in blood fats that can lead to inflammation. Many medical experts say inflammation is a core cause of heart disease.
Homocysteine Test – an amino acid toxic to blood vessels that can fuel inflammation. Have your levels checked.
Lipoprotein Test – an inflammatory form of cholesterol that increases blood stickiness and the chance of a blood clot; heart attacks and strokes come from blood clots.
Fibrinogen Test – this protein helps determine the stickiness of blood; higher than normal levels are associated with too much clotting.
C-reactive protein (CRP) – a blood protein that, when found in elevated levels, can help determine heart attack and stroke risk. C-reactive protein is a little known marker of heart disease.
Fasting Blood Sugar Test (HbA1c) – to determine risk for metabolic syndrome, a precursor to diabetes and heart disease.
Can I eat and drink before taking a blood test?
That depends upon the type of blood test performed. A healthcare professional should provide any specific instructions when your test is scheduled, including whether or not you should continue to take your medications. If not, ask for guidance on what to do prior to the test.
Examples of blood tests in which prior preparation is needed:
Iron blood test – schedule a morning test so that it can be taken on an empty stomach. Avoid taking iron pills or tablets 24 hours before the test, as it can raise your iron levels and affect results. This test determines if your iron levels are normal.
Fasting blood glucose test – don’t eat or drink anything other than water for 8-10 hours prior to the test, which is used to diagnose diabetes.
Lipid profile test – avoid foods and liquids other than water for 12 hours prior to the test. Lipid tests measure “good” and “bad” cholesterol and triglycerides in the blood.
Gamma-glutamyl transferase test (GGT) – since this test helps diagnose liver disease, don’t drink alcohol or smoke in the 24-hour period before blood is drawn, as GGT levels can be affected.
What about drug testing?
Drug testing is used in a number of ways, from medical screening to employment, legal and sports testing. Medical screening for drug abuse is usually focused on finding out what drugs, or combination of drugs, were taken so treatment can be administered.
The active ingredient in marijuana – one of the most commonly tested drugs – is THC, which enters the bloodstream rapidly. It tends to stay in the blood only a short time, however, so a urine test is more often used to detect recent marijuana usage. How long it stays in the system depends on how often or how much the user has smoked. Regular smokers have reported a positive test result up to 45 days since last usage and even longer for heavy smokers.
How do I interpret my lab report?
Lab reports can look different, as each facility has its own reporting format. Yet all contain certain information which is mandated by federal legislation. Some labs include additional information that is not required. If you have specific questions on how to read your lab reports, ask for help from your healthcare provider.
Typically, lab reports include:
- Patient name and I.D. number.
- Name and address of the laboratory location where the test was performed.
- The date the test was administered and the test report date.
- Name of the healthcare provider ordering or authorizing the test.
- Specimen source (examples: blood, urine, spinal fluid).
- Date and time of specimen collection.
- Assigned sample number called an “accession number.”
- Test name, which may be abbreviated.
- Test results, usually in a number format; may also be shown as positive or negative or in text form.
- When test results are abnormal, attention is typically drawn to the result either through highlighting, setting them apart, or indicating with an “H” for high, “L” for low, or “WNL” meaning within normal limits.
- Dangerously abnormal results are called “critical results” and must be reported immediately to the person responsible for ordering the test, most often a healthcare provider. An asterisk (*) may be used to report the date and time the responsible person was notified.
- Measurement units can vary from lab to lab. Some use kilograms or other metric forms. Many results contain a number followed by a unit of measurement. (Example: 35 milligrams per deciliter, or mg/dL).
- Reference ranges are a list of “normal” ranges in which your results are expected to fall.
- Some labs may provide interpretation of results with an explanation of what certain tests can indicate.
- Specimen conditions, especially if lab criteria is not met. One example is a specimen received in less than good condition due to collection or storage problems. In these cases, a poor specimen may be noted on the report.
- Be aware that some test results are false-positive, meaning one that shows a condition or disease is present when it is not. A false-negative test doesn’t detect what is being tested even when the condition is present. Discuss all results with a healthcare provider, including those that are inconsistent or inconclusive.
What are some helpful tips on having my blood tested if there are special circumstances?
The most important thing to remember about general lab testing is that it takes only a few minutes of your time, yet can offer a wealth of information about your overall health that is long-lasting.
Regardless, some people are highly sensitive to any type of invasive procedure including a needle prick. Children may be extremely anxious and uncooperative; the elderly have thinner skin, more fragile veins and might experience more discomfort; needle or other phobias may be present for some individuals. A relatively simple, “what’s the big deal” procedure to some can be challenging and frightening to others.
The following tips can help:
- If you have a clear phobia of needles, especially if you had a bad experience that resulted in trauma, be sure to mention it to the person taking your blood. Fainting, sweats, light-headedness and rapid heartbeat can be reduced by simply acknowledging your fear and lying down during the procedure. Most lab professionals are familiar with testing anxieties and will attempt to make the experience as easy as possible.
- Relax your muscles – close your eyes and make a conscious effort to loosen every muscle in your body.
- Take three deep, slow breaths, breathing in through your nose and out through your mouth. Slow it down if you start to feel lightheaded.
- Focus on something other than the procedure. Use visualization to put yourself in a different, more peaceful surrounding. Or think of a past, pleasant memory.
- Count to ten, concentrating on getting to the last number.
- Talk to someone. Conversation is a great method of distraction.
- If the person getting blood drawn has hearing, vision or cognitive impairments, make sure the lab is notified in advance.
- When a child is undergoing a lab test and appears unduly anxious, ask if the lab technician can speak with the child first to help explain the procedure and answer any questions. Have one or more parent (or other close adult) present in the room during the blood test.