Common Blood Tests Explained: Full Blood Count, Kidney and Liver Function

Summary

This guide explains the most common blood tests used in general medicine: the Full Blood Count (FBC), kidney function tests, and liver function tests. If you’re looking for blood tests explained in clear, plain English, this guide outlines what these tests measure, why they matter, and when it might be helpful to seek further medical advice.

Who this guide is for

This guide is for you if:

• You have recently had blood tests and don’t fully understand the results.

• Your GP has suggested repeat tests, but you’re unsure what the numbers mean.

• You are experiencing symptoms such as fatigue, palpitations, breathlessness or weight changes and wonder whether blood tests might help.

• You want to understand the difference between blood counts, kidney tests and liver tests.

If you have severe or rapidly worsening symptoms, skip this guide and seek urgent care.

Red flag checklist: when to seek urgent help

Call 999 or go to A&E immediately if you have:

• Severe or rapidly worsening breathlessness.

• Intense chest pain or a feeling of pressure.

• Fainting, sudden weakness or acute confusion.

• Heavy bleeding or vomiting blood.

• Sudden yellowing of the skin or eyes with feeling very unwell.

This clinic is not an emergency service. If your symptoms are severe, worsening quickly, or you think they may be life-threatening, call 999 or attend your nearest A&E immediately.

Why blood tests? The basics explained

Blood tests are one of the most useful tools in modern medicine. They can show:

• Oxygen-carrying capacity of the blood

• Signs of infection or inflammation

• Hydration status

• Iron, B12 and other nutrient levels

• Kidney and liver health

• Causes of fatigue or breathlessness

• Reasons for weight loss or swelling

This guide focuses on the three most commonly requested test groups.

1. Full Blood Count (FBC)

The FBC provides an overview of your blood cells.

Red blood cells

These carry oxygen around your body. Low levels may indicate anaemia, which can cause:

• tiredness

• shortness of breath

• palpitations

Anaemia has many possible causes, including iron deficiency, B12 deficiency, blood loss or chronic disease.

White blood cells

These help fight infection. High levels may suggest infection or inflammation. Low levels can indicate problems with immune function.

Platelets

These allow blood to clot properly. Abnormal numbers—either high or low—may require further investigation.

FBC results do not diagnose a specific condition but help point in the right direction.

2. Kidney function tests

The kidneys filter waste from the blood and regulate fluid balance. Key markers include:

• Creatinine

• Urea

• eGFR (estimated Glomerular Filtration Rate)

• Electrolytes (sodium and potassium)

Why they matter

Reduced kidney function can cause:

• persistent fatigue

• swelling of the legs

• high blood pressure

• breathlessness on exertion

• changes in urine output

Hydration, infections, or medications can influence results.

3. Liver function tests (LFTs)

The liver is essential for digestion, metabolism and detoxification.Common LFT components include:

Liver enzymes

• ALT and AST: indicators of inflammation or irritation

• GGT: can be raised by alcohol or certain medications

Bilirubin

High levels can cause jaundice (yellowing of the skin or eyes).

Albumin

Reflects the liver’s ability to make proteins.

Interpreting abnormalities

Abnormal results do not always mean serious liver disease. They can be affected by:

• recent viral infections

• alcohol

• medications

• exercise

• weight changes

Your doctor will look at the pattern, not a single number.

What you can safely do at home for now

If your symptoms are stable and your results are not severely abnormal:

• Stay well hydrated.

• Keep a simple record of your symptoms.

• Make a note of all medications and supplements.

• Follow your GP’s advice about repeat testing.

Avoid changing or stopping any medications without medical advice.

When to seek non-emergency medical help

1. Contact your GP if:

• Your results are slightly abnormal and need repeating.

• You have symptoms such as persistent fatigue, weight loss or itching.

• You have known kidney, liver or blood conditions.

2. Consider a consultant physician if:

• You have abnormalities in several areas (blood count, kidneys, liver).

• You have had multiple tests without a clear explanation.

• You want a full, integrated review of your symptoms and results.

• Your symptoms are persistent and affecting your daily life.

3. Online or in-person?

• Online (UK-wide): ideal for reviewing test results and planning further steps.

• In-person (Salford): useful when a physical examination is required.

How Dr Paraiso’s clinic can help

Dr Hassan Paraiso, Consultant in Acute and General Internal Medicine, helps patients understand their blood test abnormalities and develop a clear plan.

You can access his care via:

1. In-person clinic in Salford

• Location : Eric Healthcare, Bowsall House, 3 King Street, Salford, M3 7DG

• Telephone: 0121 838 1869

Appointments include a detailed review of results, focused examination and a structured plan.

2. Online consultations (UK-wide)

Ideal for discussing results, understanding what they mean, and planning next steps.

3. Direct-access blood tests (UK-wide)

Including:

• Full Blood Count

• Kidney function

• Liver function

• Iron, B12, folate

• Thyroid function

Clear written results are provided, with the option of a follow-up consultation.

Frequently asked questions

1. Can a single blood test diagnose a condition?

Not usually. Blood tests guide diagnosis rather than providing a final answer.

2. Should I worry if one number is slightly outside the range?

Not necessarily. Ranges vary with age, hydration and context.

3. Do I always need repeat tests?

Often yes, especially if a result is new or unexpected.

4. Can this be handled online?

Yes, most discussions about test results can safely be done online.

5. Will I get a clear explanation at the end?

Yes. A written summary is provided after every consultation.

Key takeaways

• Blood tests explore different aspects of your health: blood cells, kidneys and liver.

• A single abnormal number is not necessarily serious.

• Urgent symptoms require emergency assessment.

• Your GP can manage most mild abnormalities.

• Dr Paraiso offers in-person care in Salford,

  online consultations UK-wide, and direct-access blood tests.

Final safety reminder

This clinic is not an emergency service. If your symptoms are severe, worsening quickly, or you think they may be life-threatening, call 999 or attend your nearest A&E immediately.