Blood tests are one of the most common types of medical tests and have a wide range of applications.
A blood test, for example, can be used to:
- determine your overall health
- determine whether you have an infection
- examine the performance of specific organs such as the liver and kidneys
- check for specific genetic conditions
- Check if you are suitable for limb lengthening surgery
Most blood tests take only a few minutes to complete and are performed by a doctor, nurse, or phlebotomist at your GP surgery or local hospital (a specialist in taking blood samples).
Preparing for a blood test
The healthcare professional who arranges your blood test will inform you if there are any special instructions you must follow prior to the test.
Depending on the type of blood test, you might be asked to:
Fasting means not eating or drinking anything other than water for up to 12 hours – Before having a blood test, learn more about what you can and cannot eat and drink.
discontinue the use of certain medications
It is critical that you follow the instructions given to you because failing to do so may cause the test to be delayed or repeated.
What takes place during a blood test?
A blood test typically involves drawing blood from a blood vessel in your arm.
Because it is easily accessible, the arm is a convenient part of the body to use. A sample is typically taken from the inside of the elbow or wrist, where the veins are relatively close to the surface.
Blood is frequently drawn from the back of a child’s hand. Before the sample is taken, their skin may be numbed with a special spray or cream.
A tourniquet is usually wrapped around your upper arm. This compresses the arm, temporarily slowing blood flow and causing the vein to swell. This makes collecting a sample easier.
The doctor or nurse may use an antiseptic wipe to clean the area of skin before taking the sample.
In the vein, a needle attached to a syringe or special container is inserted. The syringe is used to extract a blood sample. As the needle is inserted, you may feel a slight pricking or scratching sensation, but it should not be painful. If you are uncomfortable with needles and blood, please inform the person taking the sample so that they can make you more comfortable.
The tourniquet will be released and the needle will be removed once the sample has been taken. A cotton-wool pad is used to apply pressure to the skin for a few minutes. To keep the small wound clean, apply a plaster.
After the test
Because only a small amount of blood is drawn during the test, you should not experience any significant side effects.
However, some people experience dizziness and faintness during and after the test. If this has happened to you before, inform the person performing the test so that they are aware and can help you feel more at ease.
You may have a small bruise where the needle was inserted after the test. Bruises can be painful, but they are usually harmless and fade over time.
Blood test results
After the blood sample is taken, it will be placed in a bottle and labeled with your name and contact information. It will then be sent to a laboratory to be examined under a microscope or chemically tested, depending on what is being tested.
The results are returned to the hospital or to your primary care physician. Some test results will be available the same day or within a few days, while others may not be available for several weeks. You’ll be informed when your results are ready and how you’ll receive them.
Receiving results can be stressful and upsetting at times. If you are concerned about the outcome of a test, you may choose to accompany yourself with a trusted friend or relative. You will be offered specialist counselling to help you deal with the results of some tests, such as HIV.