Your Blood Test Questions Answered: A Comprehensive UK Guide

Navigating the world of blood tests can be confusing. From the moment your blood is taken to the time you receive the results, many questions can arise. This guide provides clear, professional answers to some of the most commonly searched questions about blood tests, using a straightforward question-and-answer format to help you understand your results with confidence. All information is based on credible UK medical resources.

Question: How long do blood test results take?

Answer: The turnaround time for blood test results varies depending on the type of test. For routine screenings like a Full Blood Count (FBC) or a basic chemistry panel, results are often available within 24 to 72 hours [1]. More specialised tests, such as those for hormone levels, genetic markers, or specific antibodies, may require advanced processing and can take a week or more. The final wait time is also influenced by the lab's workload and how quickly your GP surgery reviews the results [1, 4].

Question: How do I read and interpret my blood test results?

Answer: A blood test results sheet can seem daunting, but it typically follows a clear format. You will see columns for the Test Name (e.g., Haemoglobin), Your Result, a Reference Range (the normal range for the general population), and a Flag or Marker if your result is outside that range [3]. It is crucial to remember that a result outside the reference range does not automatically indicate a serious problem. Your doctor or GP will interpret these results in the context of your personal health history, symptoms, and other clinical findings.

Question: What is a Full Blood Count (FBC) and what is RDW?

Answer: A Full Blood Count (FBC) is a very common test that provides an overview of the cells in your blood, including red blood cells, white blood cells, and platelets. It helps to detect conditions such as anaemia, infection, and some blood disorders [1, 2].

Within the FBC, RDW stands for Red Cell Distribution Width. It measures the variation in the size and volume of your red blood cells. A normal RDW means your cells are uniform in size, while an elevated RDW suggests a significant variation. An elevated RDW can be an early indicator of conditions like iron-deficiency anaemia or vitamin B12 deficiency [2].

Question: What does a high white blood cell (WBC) count mean?

Answer: A white blood cell (WBC) count is a part of the FBC. A high WBC count, also known as leukocytosis, typically indicates that your body is fighting off some form of infection or inflammation [2]. Other potential causes include an allergic reaction, physical or emotional stress, or a severe injury. While it often points to a routine issue, a persistently high count warrants further investigation by your GP to rule out other, more serious conditions [1].

Question: Why are my Liver Function Tests (LFTs) high?

Answer: Liver Function Tests (LFTs) measure various enzymes and proteins in your blood to assess the health of your liver. Elevated LFTs can be a sign of liver damage or inflammation [6]. Common reasons for high LFTs include:

• Alcohol consumption.

• Fatty liver disease.

• Side effects from certain medications.

• Viral hepatitis.

• Damage to muscle tissue (as some of the enzymes are also found in muscles).

Your GP will review which specific markers are high and in what context to determine the likely cause and necessary next steps [6].

Question: What do my kidney function test results mean?

Answer: Kidney function tests, such as Urea and Electrolytes (U&Es), assess how well your kidneys are working to filter waste from your blood. Key markers include Creatinine and eGFR (estimated Glomerular Filtration Rate). A high creatinine level and a low eGFR can indicate that your kidneys are not functioning as efficiently as they should [7]. Potential causes can range from dehydration to an underlying kidney condition. A GP will use these results to monitor your kidney health over time.

Question: Do I need to fast or prepare for a blood test?

Answer: Preparation for a blood test depends entirely on the type of test being performed. For many common tests, such as an FBC, no special preparation is needed. However, for a fasting glucose or lipid panel (cholesterol) test, your GP will specifically instruct you to fast, usually for 8 to 12 hours [1]. Fasting means you should not eat or drink anything other than water during this period. This is because food and drink can alter the levels of sugar and fats in your blood, which would lead to an inaccurate reading.

Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your GP or another qualified healthcare provider with any questions you may have regarding a medical condition.

References

1. NHS. (2024). Blood tests. Available at: https://www.nhs.uk/conditions/blood-tests/ [Accessed 6 August 2025].

2. British Society for Haematology. (2023). FBC Interpretation Guidelines. Available at: https://b-s-h.org.uk/guidelines/ [Accessed 6 August 2025].

3. Patient.info. (2025). Blood Test Results. Available at: https://patient.info/health/blood-test-results [Accessed 6 August 2025].

4. The Doctors Laboratory. (2024). About Us. Available at: https://www.tdlpathology.com/about-us/ [Accessed 6 August 2025].

5. NHS. (2025). Cholesterol. Available at: https://www.nhs.uk/conditions/high-cholesterol/ [Accessed 6 August 2025].

6. British Liver Trust. (2024). Understanding your liver function tests. Available at: https://britishlivertrust.org.uk/information-and-support/liver-health-and-risk/liver-tests/ [Accessed 6 August 2025].

7. Kidney Care UK. (2023). Understanding your blood test results. Available at: https://www.kidneycareuk.org/about-kidney-disease/diagnosis/blood-tests/ [Accessed 6 August 2025].