Receiving your blood test results can feel overwhelming. Pages of numbers, unfamiliar abbreviations, and medical terms can make even the simplest report seem confusing.
The good news is that you don't need a medical degree to get a basic understanding of what your results mean. This guide breaks down the most common blood tests in plain English, helping you feel more confident when reviewing your report.
However, it's important to remember that blood test results should always be interpreted by a qualified healthcare professional. They consider your symptoms, medical history, and overall health picture – not just isolated numbers.
Whether you've had a private blood test in London or received results through another route, this guide will help you understand the basics.
Why Blood Tests Are Important
Blood tests are one of the most valuable tools in healthcare. A small sample can reveal a wealth of information about how your body is functioning.
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Early detection – Blood tests can identify potential health issues before symptoms develop, allowing for earlier intervention
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Monitoring existing conditions – If you have a chronic condition, regular blood tests help track how well treatment is working
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Preventive health checks – Routine screening can give you peace of mind and help you make informed lifestyle choices
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Investigating symptoms – When something doesn't feel right, blood tests help identify or rule out possible causes
Understanding your results empowers you to have more meaningful conversations with your healthcare provider and take an active role in your wellbeing.
How to Read Your Blood Test Report
Blood test reports typically include several key elements. Understanding these basics will help you navigate your results more easily.
Reference Ranges
Each test result is compared to a "reference range" – the values typically found in healthy individuals. These ranges are printed alongside your results. If your value falls within this range, it's generally considered normal.
Units of Measurement
Results are expressed in specific units (g/L, mmol/L, U/L, etc.). Different laboratories may use different units, so always compare your result to the reference range on the same report rather than numbers you find online.
Flags and Indicators
Results outside the normal range are often flagged with markers like "H" (high), "L" (low), or highlighted in bold. These flags draw attention to values that may need review, but don't automatically indicate a problem.
Remember: reference ranges can vary between laboratories, and what's normal for one person may differ slightly for another. Age, sex, and other factors all play a role.
Common Blood Tests Explained
Below we explain the most commonly requested blood tests. Each section includes a table summarising what the tests measure and what abnormal results may suggest.
Full Blood Count (FBC)
A full blood count, sometimes called a complete blood count (CBC), is one of the most common blood tests. It measures your red cells, white cells, and platelets – providing a broad overview of your general health.
This test can help identify conditions such as anaemia, infections, and blood disorders. It's often used as part of routine health screening or to investigate symptoms like fatigue or unexplained bruising.
| Test Name | What It Measures | What Abnormal Results May Indicate |
|---|---|---|
| Haemoglobin (Hb) | Oxygen-carrying protein in red blood cells | Low: anaemia, blood loss. High: dehydration, lung conditions |
| Red Blood Cells (RBC) | Number of red cells in blood | Low: anaemia, bone marrow issues. High: polycythaemia, dehydration |
| White Blood Cells (WBC) | Immune cells that fight infection | Low: viral infection, bone marrow problems. High: infection, inflammation, stress |
| Platelets | Cells that help blood clot | Low: bleeding risk, bone marrow issues. High: inflammation, infection |
| MCV (Mean Cell Volume) | Average size of red blood cells | Low: iron deficiency. High: B12 or folate deficiency |
This information is for educational purposes. Always discuss your results with a healthcare professional.
Liver Function Tests (LFTs)
Liver function tests assess how well your liver is working. They measure enzymes and proteins produced by the liver and can help detect liver inflammation, bile duct problems, or damage from medications, alcohol, or disease.
| Test Name | What It Measures | What Abnormal Results May Indicate |
|---|---|---|
| ALT (Alanine Aminotransferase) | Enzyme released when liver cells are damaged | High: liver inflammation, fatty liver, hepatitis, medication effects |
| AST (Aspartate Aminotransferase) | Enzyme found in liver and muscle | High: liver damage, muscle injury, heart problems |
| ALP (Alkaline Phosphatase) | Enzyme related to bile ducts and bones | High: bile duct obstruction, bone disorders, pregnancy |
| GGT (Gamma-Glutamyl Transferase) | Enzyme sensitive to alcohol and bile flow | High: alcohol use, bile duct issues, fatty liver |
| Bilirubin | Waste product from red blood cell breakdown | High: liver disease, bile duct blockage, Gilbert's syndrome |
| Albumin | Protein made by the liver | Low: chronic liver disease, malnutrition, kidney problems |
This information is for educational purposes. Always discuss your results with a healthcare professional.
Kidney Function Tests
Kidney function tests (also called U&Es or renal function tests) measure how well your kidneys are filtering waste from your blood. They're important for monitoring hydration, kidney disease, and the effects of certain medications.
| Test Name | What It Measures | What Abnormal Results May Indicate |
|---|---|---|
| Urea | Waste product from protein breakdown | High: kidney impairment, dehydration, high protein diet |
| Creatinine | Waste product from muscle metabolism | High: reduced kidney function, dehydration, muscle injury |
| eGFR | Estimated kidney filtration rate | Low: reduced kidney function, chronic kidney disease |
| Sodium | Essential electrolyte for fluid balance | Low: overhydration, certain medications. High: dehydration |
| Potassium | Essential electrolyte for heart and muscles | Low: diuretics, vomiting. High: kidney problems, certain medications |
This information is for educational purposes. Always discuss your results with a healthcare professional.
Thyroid Function Tests
Thyroid function tests measure hormones that regulate your metabolism. An underactive thyroid (hypothyroidism) or overactive thyroid (hyperthyroidism) can cause a range of symptoms including fatigue, weight changes, and mood disturbances.
| Test Name | What It Measures | What Abnormal Results May Indicate |
|---|---|---|
| TSH (Thyroid Stimulating Hormone) | Hormone that stimulates thyroid gland | High: underactive thyroid. Low: overactive thyroid |
| Free T4 (Thyroxine) | Main thyroid hormone | Low: underactive thyroid. High: overactive thyroid |
| Free T3 (Triiodothyronine) | Active thyroid hormone | Low: hypothyroidism, illness. High: hyperthyroidism |
| Thyroid Antibodies | Antibodies against thyroid tissue | Positive: autoimmune thyroid disease (Hashimoto's, Graves') |
This information is for educational purposes. Always discuss your results with a healthcare professional.
Cholesterol & Lipid Profile
A lipid profile measures fats in your blood, including cholesterol and triglycerides. These results help assess your cardiovascular risk and guide lifestyle or treatment decisions.
| Test Name | What It Measures | What Abnormal Results May Indicate |
|---|---|---|
| Total Cholesterol | Overall cholesterol level in blood | High: increased cardiovascular risk, dietary factors, genetics |
| LDL Cholesterol | "Bad" cholesterol that can build up in arteries | High: increased risk of heart disease and stroke |
| HDL Cholesterol | "Good" cholesterol that helps remove LDL | Low: increased cardiovascular risk. Higher levels are protective |
| Triglycerides | Fat from food stored for energy | High: diet, obesity, diabetes, alcohol, very high levels can cause pancreatitis |
| Non-HDL Cholesterol | Total cholesterol minus HDL (all "bad" fats) | High: increased cardiovascular risk |
This information is for educational purposes. Always discuss your results with a healthcare professional.
What Can Affect Your Blood Test Results?
Several factors can influence your blood test results, sometimes leading to values outside the normal range even when there's no underlying health problem.
Diet and Fasting
Recent meals can affect glucose, triglycerides, and other markers. Some tests require fasting for accurate results.
Medications and Supplements
Many medicines and supplements can influence results. Biotin, for example, can affect thyroid and other tests.
Hydration Status
Dehydration can concentrate your blood, making some values appear higher than they truly are.
Recent Illness
Infections and inflammation can temporarily alter liver markers, white blood cell counts, and other values.
Timing of the Test
Some hormones fluctuate throughout the day. Cortisol, for instance, is highest in the morning.
Exercise
Intense physical activity before a test can affect muscle enzymes and other markers.
Always inform your healthcare provider about any factors that might have influenced your results. They can take these into account when interpreting your report.
When Should You Be Concerned?
Seeing a result flagged as "high" or "low" can feel alarming, but it's important to keep perspective.
Key Points to Remember
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Trends matter more than single results – A pattern over several tests is more meaningful than one isolated reading
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Mild abnormalities are common – Many people have slightly out-of-range results that require no action
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Context is everything – Your healthcare provider considers your symptoms, history, and overall health picture
Disclaimer
This article is for educational purposes only and is not a substitute for professional dental advice, diagnosis, or treatment. Individual conditions vary — please consult a qualified dental professional for personalised guidance. In a dental emergency, seek immediate professional care.