Why do I need a blood test?
Because blood is the body’s main carrier of nutrients, waste products and oxygen, it offers physicians a very important tool for diagnosing and monitoring health. Many forms of disease can be detected by various types of blood tests. Blood can be tested for many different factors. For example, the doctor may need to know the number of red or white blood cells present, or the amount of oxygen or carbon dioxide circulating in the blood.
What are the different types of blood test?
While numerous different blood tests are performed every day in laboratories. Generally speaking there are five main types of blood tests: Haematology, Biochemistry, Blood Transfusion, Microbiology and Serology.
- Determine the numbers and types of blood cells that are present, their appearance and state of maturity.
- The ability of blood to form clot and how quickly that occurs.
- Measure the levels of normally occurring chemicals in the blood. These results are compared to normal ranges and are used to determine whether blood chemicals are in a proper and healthy balance.
- These tests can be used to indicate how well some organs and organ systems are functioning. For example, the amount of blood sugar (glucose) in the bloodstream can help diagnose or monitor diabetes, and indirectly reflect how much insulin is being produced by the pancreas.
Blood Transfusion tests:
- Identify an individual specific blood type and whether they have any unusual or rare blood antibodies.
- Examine blood for the presence of infectious microscopic organisms such as bacteria, viruses, fungi and parasites.
- Detect the presence of specific antibodies that are produced by white blood cells. They are frequently used to detect viral diseases.
Do I need to do anything to prepare for a blood test?
Preparation for blood tests varies according to the requirements of each specific test. In most cases minimal preparation is necessary. You may need to reduce or stop certain medications at some point prior to the test. Sometimes, food intake and exercise may need to be temporarily restricted or suspended. Your doctor will advise you in advance of any specific preparations you need to make prior to your blood test. Alcohol and caffeine should be avoided prior to a blood test.
What blood tests do I need to fast for?
Obtaining a blood sample takes only about five minutes, and most patients find the procedure to be virtually painless. For most blood tests, there is very little preparation, and people can generally go right back to their usual daily activities afterwards. Your doctor will advise you on any specific preparations you need to make prior to giving the blood sample.
Fasting is generally required for the following tests:
- Glucose Tolerance (GTT) tests require an initial fasting sample, plus a second sample taken two hours after eating.
- Serum lipids, for example cholesterol and triglycerides.
What is involved in giving a blood sample?
Blood is usually drawn from a vein in a process called venipuncture. The person taking the blood sample is called a Phlebotomist. During a venipuncture, the Phlebotomist inserts a needle into a vein – usually at the inside of the elbow. The area around the puncture site is cleaned with rubbing alcohol and a wide elastic band called a tourniquet, is placed around the upper arm to slightly increase the pressure in the vein. One end of a sterile double–ended needle that has been attached to an open–ended syringe (which contains an empty test tube) is inserted into the vein. Because the test tube contains a partial vacuum, blood flows directly from the vein through the double–ended needle and into the test tube. The precise amount of blood to be drawn is determined by the type and number of tests to be done. The phlebotomist may change test tubes once or twice during the venipuncture to either allow for more blood to be collected or to change the type of tube being used: After the necessary amount of blood is drawn, the needle is withdrawn and a small cotton ball or pad is applied with light pressure over the puncture site. After several minutes, the cotton will be discarded or replaced, and a small bandage will be placed on the puncture wound. The entire process takes less than 10 minutes. After giving the blood sample, patients may resume medications and food intake according to their physician’s orders.
How soon do I get the test results?
All your blood test results will be sent directly to your doctor. Most blood tests results should be received by your doctor within about 3 days. Certain blood tests, for example Microbiology and Serology tests take longer to process but generally should be available with 7 days.