Understand Your Blood Test Results

A low haemoglobin is called anaemia. The most common cause in the UK is iron deficiency, often from poor dietary intake or blood loss. Looking at your MCV (red blood cell size) alongside haemoglobin helps identify the type — a low MCV points to iron deficiency, while a high MCV points to B12 or folate deficiency.

The normal range for TSH (thyroid stimulating hormone) in UK laboratories is typically 0.4 to 4.5 mU/L. A raised TSH indicates an underactive thyroid (hypothyroidism). A suppressed TSH indicates an overactive thyroid (hyperthyroidism) or over-treatment with levothyroxine.

ALT (alanine aminotransferase) is the most sensitive marker of liver cell damage. A mildly raised ALT (up to three times the upper limit) is common with fatty liver disease, alcohol intake, and certain medications such as statins. A raised ALT alongside a raised GGT in a patient who drinks alcohol is the classic pattern of alcoholic liver disease.

HbA1c measures your average blood glucose level over the previous 2 to 3 months. An HbA1c of 48 mmol/mol (6.5%) or above on two separate tests confirms a diagnosis of type 2 diabetes. A reading of 42 to 47 mmol/mol (6.0 to 6.4%) indicates prediabetes.

eGFR (estimated glomerular filtration rate) measures how well your kidneys are filtering your blood. A normal eGFR is above 60 mL/min/1.73m². An eGFR below 60 on two occasions at least 90 days apart defines chronic kidney disease (CKD). The lower the eGFR, the more advanced the CKD.

LDL (low-density lipoprotein) is often called 'bad cholesterol' because it deposits cholesterol in artery walls. For most people, an LDL above 3.0 mmol/L warrants consideration of lifestyle changes or statin therapy based on overall cardiovascular risk. For people who have had a heart attack or stroke, the target is below 1.4 mmol/L.

Ferritin is the main storage protein for iron. A ferritin below 30 µg/L indicates depleted iron stores, even if your haemoglobin is still normal. Below 15 µg/L confirms iron deficiency. Symptoms such as fatigue and brain fog can occur even before anaemia develops.

GGT (gamma-glutamyl transferase) is the most sensitive marker of alcohol-related liver changes. It can be elevated by regular alcohol intake even before any structural liver damage occurs. GGT also rises with biliary obstruction and is used to confirm whether a raised ALP is from the liver or from bone.