Understanding your blood test results - Frequently Asked Questions

General Health


Helen Marsden

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1. How will my blood test results be reported to me?

The vast majority of blood test results will be reported according to whether they fall within the test's reference range. Normally, results which fall outside the range are marked by the laboratory with an asterisk. At Medichecks we make the process of spotting results which are outside the reference range even easier by displaying your results in a personalised dashboard using traffic light colours to guide you.

2. What do the blood test reference ranges mean?

The reference range of many tests is determined by the laboratory by taking a universe of what are considered normal participants and looking at the variation in their test results. The reference range is normally set at a value whereby the middle 95% of the participants fall into that range.

For other blood tests the range is established by target ranges as opposed to the distribution of results in a normal population. For example, if a vitamin d test were performed on a large number of people in the north of England in the middle of winter, 95% or the participants would probably have low levels of vitamin d. While this might be normal, it isn't optimum, so the range the laboratory would give would be based on target levels. Similarly the ranges in your Cholesterol Check are determined by what is considered healthy as opposed to what the distribution of results might be in the normal population.

3. One of my blood tests results is outside the reference range - should I be worried?

Given that 5% of the universe of normal participants used to establish the range are outside the 95% distribution, then it is clear that it is perfectly possible to have a result outside that range and be considered "normal". Indeed, in a typical health screen like our Essential Blood Screen which contains over 40 individual tests, it is extremely common to find one or more test results outside the reference range. Often these are what would be considered a variation of the norm and would be reported as such.
When our medical team are reviewing results they don't just look at the result in isolation; sometimes a result, a pattern of results, or results combined with other risk factors such as family history would signal that further investigations should be made. In this instance we would suggest further tests or that you should seek advice from your usual doctor. We also take into consideration your own health history, for example a low urea is rarely significant except in a patient with chronic liver disease when it indicates low protein metabolism. This is why it is important to fill in our health and lifestyle questionnaire before we interpret your results as it helps us to put your blood test results into context.

4. Why does it matter what age I am?

For some blood tests the age of the patient is not relevant, however, there are many where age is an important factor. For example, children who are growing quickly would show much higher levels of growth hormones like IGF-1 than adults.  High levels of IGF-1 in children is necessary for growth but could be cancer promoting in adults. This is why the reference range will change for some tests according your age.

5. Why was I asked about my gender?

Your gender is another important factor in some tests, especially hormone blood tests; while men and women both produce testosterone, levels which are normal in men would be considered abnormal in women.

6. What other factors can influence my blood test results?

There are a number of other factors which can influence your blood test results some of which are obvious and some of which might surprise you! Your hormone tests might be influenced by the time of day (or for women the time of the month) that you performed the test; your Cholesterol Check and Diabetes Check (blood sugar) will be influenced by what and when you last ate which is why we prefer a fasting blood sample; a man's Prostate Check (PSA test) could be raised if he has recently ridden a bicycle or has ejaculated, and a Liver Check can reveal raised liver enzymes if you conducted a vigorous gym session the day before you took your blood test. At Medichecks we try to find out as much information as we can about your medical history and lifestyle before we interpret your results to see if there are innocent factors which might explain out-of-range results. Even your ethnicity can impact your results; we are more likely to see a lower white cell count in people of black African descent than we are for other races.

7. I've been advised to have a re-test - how quickly will changes show up in my blood tests results?

We normally advise a re-test for out-of-range results, often because a result might be raised because of an innocent factor, or because you might be suffering from an infection or virus which has caused a temporary rise in say an inflammation marker or your white cell count, or even to give you the opportunity to make lifestyle changes which could see your blood biomarkers improve. In our report we will recommend how quickly to re-test; four to six weeks should be sufficient time for a virus to disappear, whereas it is unlikely to be long enough for a new exercise regime to impact your blood sugar levels.
Sometimes we don't advise the same test be repeated but suggest a different test which can drill down and provide more information about a result. For example, if you have a raised blood sugar result we are likely to suggest a test for HbA1c (glycosolated haemoglobin) which is a measure of your blood sugar levels over the past 8 weeks or so. This can tell us if the first result was a temporary blip or the beginnings of type 2 diabetes.

8. Can I compare my Medichecks blood test results with the results of my previous provider?

This will depend on whether your previous tests were conducted at the laboratory we use or a different one. This is because the reference ranges, testing protocols and even the units of measurement might differ from laboratory to laboratory. It is much more important to look at whether the result was in range or not, and compare that with your previous results.

Remember, if you have any questions about your blood test results then please give our team a call on  08456 029 029,  we're always happy to help and advise.


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