What do blood tests show?

Why would a blood test be carried out?

Blood tests may be carried out to test for a number of different health conditions, as well as being carried out to monitor an individual’s condition and used to assess the effectiveness of a treatment or medication.

Blood tests assess levels of different chemicals, cells and enzymes in the blood; a normal reading may indicate that a person is healthy, while low or high levels may indicate that a person has an illness or infection.

Blood tests are very common; most people will have a number of blood tests during their lifetime. In many cases, blood tests are done as a routine check on a person’s general health. However, if a person is experiencing symptoms of an illness or infection, they may have a blood test to determine what the problem is; a blood test is an important diagnostic instrument.

There are a number of different blood tests, which can be done to determine different results; different blood tests can be carried out to assess the components of your blood, assess your risk of heart disease and test for specific infections, for example.

What do the results show?

Abnormal levels of certain structures or chemicals may indicate that an individual has an illness or infection; the nature of the results will determine the specific illness, for example, a low red blood cell count may indicate that an individual has anaemia.

Once a blood sample has been analysed by a technician, the results will be returned either to the GP or the hospital; the doctor will then interpret the results and explain them to the patient. The results are compared with guidelines to establish whether they are normal or abnormal.

In many cases, blood tests cannot be used to diagnose a specific illness and further tests may be required; however, they are a useful diagnostic tool and can be very helpful for doctors to reach a diagnosis.

Sometimes, results may be slightly higher or lower than normal and this may not necessarily indicate that an individual is unwell; certain factors, such as alcohol intake, drug intake, taking certain medications, diet and a recent injury can influence the results and you may be advised to have a repeat test so that the doctors can reach an accurate diagnosis.

How are the ‘normal’ levels determined?

In most cases, the guidelines are determined by the average levels seen in 96 percent of the population; this includes healthy individuals. If you are borderline, you may be advised to have another test in the near future so that your condition can be monitored but if your levels are significantly higher or lower than the ‘normal’ level, you will offered treatment and your condition will be monitored closely.

‘Normal’ levels may differ according to your age, sex and race and these factors will be taken into account when the doctor interprets your results.

What happens if my test shows abnormal results?

If your test comes back with abnormal results, your doctor will explain the results to you and discuss appropriate treatment options with you.