Blood test results: what do abnormal results mean?

What does an ‘abnormal’ blood test mean?

These days, many people receive their blood test results directly through electronic records like the NHS App or via a text message from their GP surgery, often before a doctor can talk them through.

This can understandably cause concern if you’re not sure what the results mean.

It’s important to know that blood test results are compared against ‘reference ranges’, which are typical values used for the general population. If a result falls outside this range, the computer may flag this as ‘abnormal’.

These flags are generated automatically and do not always mean something is wrong. For example, terms like ‘high cardiovascular risk’ or ‘borderline diabetes’ are auto-generated by computer systems.

This can be helpful for doctors to see, as it helps them decide whether they need to take further action.

What can cause abnormal blood test results?

There are many reasons why a blood test might display an ‘abnormal’ result. While the computer will flag a result if it's outside the ‘normal’ range, this does not mean there is a cause for concern.

In some cases, an abnormal result is expected – if you already have a known condition, your usual levels may fall outside the standard reference ranges.

Sometimes, a result may be only slightly higher or lower than the reference range, and no further investigation is needed. Some results may mean your doctor will need to arrange a follow up or begin treatment.

If you're taking medicines or have had a recent illness, you may also get an abnormal test result. This may be temporary or something expected, but your doctor will explain this to you.

What should I do if I have an abnormal blood test? 

If you receive an abnormal result, try not to worry. It does not automatically mean you have a diagnosis.

It’s important to remember that, even though it’s on your results, it might not mean that it’s either abnormal for you or that you have a new condition.

If you’re worried about what your results mean and no one has contacted you, get in touch with your GP surgery to ask what to do next.

How quickly will the doctor call with the blood test results?

Once you’ve had your blood test, it can take a few days for the results to come back, depending on the type of tests you’ve had. You may be asked to call back for your results, or you may receive them electronically through the NHS App, for example.

If further action is needed on your results, your doctor or nurse will be in touch. They may ask you to come in for an appointment or book one over the phone. They may also ask you to have a repeat blood test to check that the results are accurate.

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