Blood tests have numerous uses, and are most often the first step to investigating or diagnosing a condition.
During a blood test, a blood sample is taken from a blood vessel which is usually within your arm. The veins here are relatively close to the surface, therefore are easy to access. A tourniquet is placed around the top of your arm, which causes the vein to swell making it easier for a sample to be taken. A needle is then inserted into the vein, and the blood sample is retrieved and sent away for analysis.
Some blood tests require you to fast beforehand, which means no eating and drinking for a set period of time prior to the blood test. You may have to stop taking certain medication beforehand, which your doctor or nurse will advise you of.
After the test, you shouldn’t feel any significant side-effects. You may feel dizzy, but this will quickly pass. You may also have a small bruise where the needle was inserted, but this will fade over the next few days.