Introduction: A New View of You If you''re like most people, a blood test is an event that comes once a year along with your annual physical. Ideally, within a week, your doctor calls with the results, assuring you that they are normal. You may even receive a copy of the test in the mail, complete with columns of numbers supposedly confirming your health, but to you are probably meaningless and confusing. So you put the results aside, file them away with your other personal records, and carry on with your life free of concern. After all, the doctor says you are in the "normal range," so why worry? While this may be the case, blood tests still raise important questions that even the healthiest of patients should be asking: Does "normal" necessarily mean "healthy"? What can the lab values of a blood test tell me about the current state of my health? And, perhaps more importantly, what can these lab values tell me about my health in the future? The fact is, blood testing generally has one purpose, and that is to check for disorders, dysfunction, and disease. When blood test results point to a certain condition, measures are taken to bring the appropriate number-the abnormal lab value-into the "normal" range. However, when test results are normal, only rarely is a patient told how to stay in this range or, better yet, how to achieve an optimal, or target, level. It becomes a matter of waiting for the other shoe to drop, leading up to the day when you walk into the doctor''s office or pick up the phone and are told, "You are diabetic" or "You have a thyroid disorder.

" But it does not have to be this way. A blood test is essentially a blueprint of your health and a glimpse of its future. It tells you so much about what is going on inside your body, and it can speak volumes about what may go on inside of it somewhere down the line. The information obtained from lab results can push you to take the needed steps to put (or keep) your health on the right track. A blood test can motivate you to change your dietary habits, start a fitness regimen, or alter certain aspects of your lifestyle, such as your stress level and sleep patterns. A blood test can also be precautionary, helping you to monitor conditions that may be a running concern in your family or personal medical history. If you are already being treated for a particular condition, a blood test is one of the best ways to ensure that your medication is doing its job. In sum, a blood test is a quantitative way of measuring your health so that you can manage it more effectively and easily.

But before you can begin to interpret your test results, you should know a thing or two about the blood testing procedure, as well as certain factors that may influence the outcome. [B] THE BASICS OF BLOOD TESTING A blood test is a common medical procedure in which a small amount of blood is drawn from the body using a needle, which is usually inserted into a vein in the arm. The blood sample is then analyzed by a lab technician to check for any sign or risk of disease, organ dysfunction, nutritional deficiency, or other problem. The technician may examine whole blood or separate the blood cells from the fluid in which they are contained, which is known as the serum or plasma . The plasma is used to measure levels of various substances in the blood and determine whether or not they fall into the normal range. This range is based on the average values reported in 95 percent of healthy people of a certain group and, therefore, may vary according to factors such as age, sex, and ethnicity. The reference ranges for normal, high, and low lab values may vary among laboratories depending on the methodology used by the blood analysts. The ranges used in this book reflect the guidelines set by LabCorp, a company that provides testing services to nearly 90 percent of doctors'' offices, hospitals, and other medical institutions.

(See the "Resources" section on page 000 for a listing of LabCorp reference ranges.) However, some labs may use slightly different ranges, so you should take this into account when reviewing your blood test results. Standard blood tests are not always completely accurate. There are a number of factors that may artificially cause your blood levels to fall outside the normal range, resulting in an abnormal reading or false-positive result. Certain foods, physical activity, alcohol and caffeine consumption, and some medications affect metabolism and overall body function, and thus may influence blood test results. Failing to follow pre-testing instructions, such as fasting, can also produce abnormal results. By the same token, standard blood tests can indicate normal blood levels when a disease or other condition is actually present, or a false-negative result. The bottom line is that abnormal results may, but do not always, indicate a health problem.

If your results show an abnormality, do not panic. Your physician will probably recommend more specific blood tests, which have a higher rate of accuracy. In general, a blood test is quick and requires little preparation. If you are unfamiliar with the procedure or if it has been a long time since your last blood test, here is a rundown of what you can expect before, during, and after the test. [C] Before the Blood Test One of the most common questions people have about blood tests is whether or not they can eat beforehand. Most healthcare professionals recommend fasting for approximately eight hours prior to a blood test. To "fast" generally means to abstain from food and beverages, especially coffee, tea, and alcohol. These liquids in particular should not be in your system for ten to twelve hours before the test, as they can skew readings.

However, fasting does not include water, which you should continue to drink not only to prevent dehydration, but also the lightheaded and dizzy feeling that may accompany the loss of even a small amount of blood. If your doctor or health practitioner does not mention fasting, it is best to ask, as it may be advisable to fast for more than eight hours to ensure the accuracy of certain tests. Pre-test preparations may also be tailored to a specific health concern, such as triglycerides or blood sugar. If you are worried that your triglycerides level is high, you may want to avoid fatty foods the day before the test, as these can artificially raise the fat content of your blood and cause a high reading. Even a seemingly harmless food such as salad dressing (unless it is fat-free) can inflate your triglycerides level. If you are concerned about high blood sugar, refrain from eating foods rich in carbohydrates the day before the test, since they remain in your system longer than other foods. Still, many of your blood levels will not change significantly in the short term, especially if your body is functioning normally. Fasting has the greatest impact on blood sugar, insulin, and triglycerides, so stay away from foods and liquids that can temporarily raise these levels.

Keep in mind, though, that there are many blood tests that may require special preparation, so always inquire ahead of time about pre-testing instructions. Finally, be sure to tell your doctor or health practitioner if you are taking blood thinners, such as heparin and warfarin (Coumadin), or any other medication, whether prescribed or over-the-counter (OTC). Since medications may interfere with test results, your doctor should be aware of this information before the blood test is administered. [C] During the Blood Test Although self-testing kits are now available from online retailers, you should have your blood tested at a doctor''s office, lab, or hospital. Drawing blood is not a foolproof procedure and, therefore, should be done by a phlebotomist- a specialist trained in drawing blood samples for medical analysis. A skilled phlebotomist should be able to find a vein and draw the blood in a single attempt without causing a patient to feel significant pain or discomfort. Most people feel only a brief pinch when having their blood drawn. Of course, not all phlebotomists are equally skilled at finding veins or inserting needles, so if a vein cannot be found after two tries, you should ask that another technician take your blood instead.

While blood tests are generally neither complicated nor painful, there are a couple things you can do immediately before the test to ensure the procedure is as comfortable and stress-free as possible. First, increase your water intake about an hour before the test, since water helps to fill up the veins, making them "plumper" and more easily accessible. Second, place a warm towel or heating pad on your arm as you sit in the waiting room. Like water, warmth makes veins less constricted so that the technician taking your blood can easily locate a vein and insert the needle, thereby minimizing discomfort. You will probably be sitting in a chair or on an examining table for the blood test. Once you are comfortable, the phlebotomist will apply a tourniquet and touch your arm with one or two fingers, feeling for a vein. You may be asked to make a fist to make the veins in your arm more prominent. When the vein is located, the area will be cleaned by applying rubbing alcohol with a cotton swab.

Then, it is finally time to draw the blood. To reduce your anxiety, look away from the needle and focus on another object in the room, or simply close your eyes. Try to relax your arm and make sure you keep it still. Once the needle is in, the hardest part is over-the test will be done in a matter of minutes. [C] After the Blood Test Once the needle has been withdrawn from your arm, you will probably be asked to bend your arm and apply pressure to the area while the phlebotomist gets a bandage. Let her know if you are sensitive or al.