Medically Reviewed by Dr. Andrew Stein MD, Consultant Nephrologist (Hospital Kidney Specialist). Last updated: June 2026
Understanding (and monitoring) your blood test results – often called ‘normal labs’ – is a vital part of managing your health.
Having a baseline knowledge, helps you have more informed conversations with your doctor.
In this guide, we break down the 10 most common blood tests (or groups of), their normal ranges, and what it means when your levels are high or low.
In the UK, ‘normal’ is defined by a Reference Range based on a healthy population. However, these ranges can vary slightly between NHS hospitals and laboratories.
Biological Variation: Your age, sex, and even the time of day can impact results.
Lifestyle: Hydration, recent exercise, and fasting status (crucial for Glucose and Lipids) are key.
The Trend: A single result is just a data point; a series of results over time tells a much more accurate story of your health.
The FBC is a ‘snapshot’ used to screen for anaemia, infection, and clotting disorders.
| Component | Normal Range (Adults) | High Result May Indicate | Low Result May Indicate |
| Haemoglobin (Hb) |
M: 130–170 g/L
F: 110–150 g/L |
Polycythaemia (dehydration, smoking, lung disease). | Anaemia (many causes including blood loss, iron deficiency). |
| White Cell Count | 4.0–11.0 x 10⁹/L | Infection, inflammation. | Viral infections, bone marrow issues. |
| Neutrophils | 2.0–7.5 x 10⁹/L | Bacterial infection. | Viral infection, chemotherapy. |
| Lymphocytes | 1.0–4.0 x 10⁹/L | Viral infection, some leukaemias. | Immunodeficiency, steroids. |
| Platelets | 150–400 x 10⁹/L | Reaction to surgery or infection. | Risk of easy bruising/bleeding. |
| MCV (Cell Size) | 80–100 fL | B12 or folate deficiency. | Iron deficiency or thalassaemia. |
This panel measures how well your kidneys filter waste and maintain mineral balance.
Sodium (Na): 135–145 mmol/L. Critical for brain function. Levels below 125 or above 150 require urgent medical attention.
Potassium (K): 3.5–5.3 mmol/L. Vital for heart rhythm. Values <3.0 or >6.0 are medical emergencies.
Creatinine: 60–120 μmol/L. High levels suggest Acute Kidney Injury (AKI) or Chronic Kidney Disease (CKD).
eGFR: >90 ml/min. Think of this as your kidney’s ‘efficiency percentage.’ Patients may have CKD, if GFR is <60 ml/min twice in a three month period. However GFR naturally falls by ~10 ml/min per decade after age 40. So a GFR of 50 ml/min can be normal for an 80 year old – and is not CKD.
Urea: 2.5–7.8 mmol/L. High levels suggest dehydration or reduction in kidney function (similar to creatinine).
Bicarbonate: 22–28 mmol/L. Helps balance pH; high/low levels indicate metabolic issues.
Note: If your Urea is high but your Creatinine is normal, it often simply means you are dehydrated or have recently had a very high-protein meal.
LFTs measure enzymes and proteins produced by the liver. They are also called ‘liver enzymes’. High levels of enzymes often indicate liver inflammation or damage, or bile flow issues.
ALT & AST: 7–56 U/L; 10–40 U/L. Enzymes that leak into the blood if liver cells are damaged (e.g fatty liver, alcohol, hepatitis).
Bilirubin: <21 µmol/L. High levels occur in jaundice (yellowing of skin/eyes).
Albumin: 35–50 g/L. A protein made by the liver; low levels suggest chronic illness, malnutrition or some kidney diseases.
ALP: 30–130 U/L. High levels suggest bile duct issues or bone disorders.
GGT: M: 10–71 / F: 6–42 U/L). Often used to screen for alcohol excess or bile duct obstruction.
These markers check the health of your skeletal system and mineral balance.
Calcium: 2.2–2.6 mmol/L. Essential for bones and nerve signals.
Phosphate: 0.8–1.4 mmol/L. Can rise in CKD.
Magnesium: 0.7–1.0 mmol/L. Low levels (hypomagnesaemia) can cause muscle cramps and heart rhythm issues.
Vitamin D: >50 nmol/L. Necessary for calcium absorption.
These tests measure how your body processes sugar.
Fasting Glucose: 4.0–6.0 mmol/L. Levels >7.0 (fasting) or >11.0 (random) mmol/L suggest diabetes.
HbA1c (average sugar over 3 months):
Normal: <42 mmol/mol (<6.0%)
Prediabetes: 42–47 mmol/mol (6.0–6.5%). Dietary control required.
Diabetes: 48 mmol/mol (6.5%+) or higher.
This test measures the fats in your blood to assess cardiovascular risk.
Total Cholesterol: Desirable <5.0 mmol/L.
HDL (Good): >1.0 mmol/L. Protects the heart.
LDL (Bad): <4.0 mmol/L. Can clog arteries.
Triglycerides: <1.7 mmol/L. Linked to sugar/alcohol intake.
TSH: 0.4–5.0 mU/L. High TSH = Underactive (Hypothyroidism); Low TSH = Overactive (Hyperthyroidism).
Free T4: 8.0–18.0 pmol/L. The actual hormone levels in the blood.
CRP: <5 mg/L. The body’s ‘general alarm’ – i.e. indicates an acute illness somewhere. High levels indicate infection or injury.
ESR: <20 mm/hr. Measures ‘smouldering’ or chronic inflammation.
Iron (Ferritin): (M: 30–400 / F: 15–200 µg/L). Reflects iron stores.
Iron Saturation (Transferrin Saturation): 20–45%. Low Tsat with low Ferritin confirms iron deficiency. High Tsat (>50%) can be an early warning for Haemochromatosis (iron overload).
Vitamin B12: >190 ng/L. Low levels cause ‘large cell’ (macrocytic) anaemia.
Folate (Vitamin B9): >3.0 µg/L. Also causes macrocytic anaemia.
NT-proBNP: <400 pg/mL. Levels >400 indicate the heart is struggling to pump blood effectively (heart failure).
PSA: <3.0 ng/mL. Prostate screen (men only). Elevated PSA can indicate prostate cancer, but it is also raised by age, infection (prostatitis), or non-cancerous enlargement (BPH).
INR: 0.8–1.1. This measures how quickly your blood clots. Patients on blood thinners like Warfarin will have a higher target range (usually 2.0–3.0) to prevent strokes or clots. Also used as a marker of liver function.
Contact a doctor immediately if you see these values on your results:
Potassium: <3.0 or >6.0 mmol/L (Heart rhythm risk).
Glucose: >15.0 mmol/L (Risk of ketoacidosis).
Haemoglobin: <70 g/L (Severe anaemia; may need transfusion).
Lactate: >2.0 mmol/L (Sign of severe infection/sepsis).
Oxygen Saturation: <90% (Respiratory distress).
Note: Always consult your GP or hospital consultant (or nurse) to interpret your specific results. Small deviations may be normal for you.
Why are my results different from these ranges?
Laboratories use different equipment and ‘reference populations.’ So the ‘normal range’ (in brackets) may be slightly between clinics. Always use the range printed on your specific lab report.
What is CRP?
C-Reactive Protein (CRP) is a marker of inflammation or injury. High levels tell doctors there is ‘trouble at the mill’—meaning infection, injury, or an autoimmune flare-up—but it doesn’t specify where the problem is.
Why is my HbA1c result different from my daily finger-prick glucose readings?
My result is ‘borderline’ or marked in red/bold—should I be worried?
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