Common Health Questions

What do my blood test results mean?

This question cannot be answered in general terms because your blood test results are specific to you. Your GP, or the healthcare professional who arranged the test, needs to interpret the results because only they have all the information necessary to do so.

Your personal medical history

Your test results will only make sense when taking into account your personal medical history, and only your GP or consultant has access to this information.

For example, if your blood glucose (sugar) is tested and the result is low, this could be a sign of Addison’s disease (a condition that affects the adrenal glands). However, if you have diabetes, it’s more likely to mean you’ve taken too much diabetes medication. Without knowing what medical conditions you have and what medication you’re on, the test results could be misinterpreted. 

Also, only your GP or consultant will know why you needed the test and what other tests you’ve had. It may be that all of your test results need to be assessed together.

For example, a full blood count can be used to measure all the different types of blood cells in the sample and diagnose anaemia (lack of red blood cells). However, without also looking at the results of your tests for ferritin (a protein that stores iron), vitamin B12 and folate, it won’t be clear what’s causing your anaemia and therefore what treatment you need. 

Different laboratories

Results for the same type of test can be expressed differently by different medical laboratories. This is because laboratories have different: 

  • equipment
  • testing methods
  • reference ranges

Reference ranges are used by laboratories to identify what they consider a normal range for test results. They calculate their reference ranges based on a large number of tests and work out the average.

As well as your test results, the laboratory will provide details of their reference range to your GP or consultant, who can then compare your results to the average. It’s not possible to interpret your test results without this information. As explained above, your GP or consultant also needs to take your personal medical history into account.

Other factors that can affect test results

Your test results can also be affected by:

  • your age
  • your sex
  • when the test was carried out, for example morning or evening
  • how much alcohol you drink
  • your diet
  • whether you smoke  
  • whether you’re stressed or anxious
  • whether you’re pregnant 
  • how much physical activity you do

This means that your test results will be different to someone else’s, even if they have the same medical condition as you.

It’s important to follow any instructions your healthcare professional gives you before the test, for example not to eat or drink.

If you have any questions about your test results, you should ask your GP or the healthcare professional who arranged the test.

Last Updated: 02 December 2011