Blood Results 🧪

📋 Overview

Blood results are a core part of patient assessment. Recognising abnormal values quickly and understanding likely causes is critical on-call.
The tables below list common tests, their normal reference ranges, and possible causes for abnormal results.

🩸

Full Blood Count (FBC)

Essential haematology parameters

Test	Normal Range	High Causes	Low Causes
Hb	13-18 g/dL (M), 11.5–16.5 g/dL (F)	Dehydration, polycythaemia	Anaemia, bleeding, CKD
WCC	4–11 ×10⁹/L	Infection, inflammation, leukaemia	Aplastic anaemia, chemotherapy, viral infection
Platelets	150–400 ×10⁹/L	Inflammation, iron deficiency	ITP, DIC, sepsis

Hb

Normal Range:

13-18 g/dL (M), 11.5–16.5 g/dL (F)

High Causes:

Dehydration, polycythaemia

Low Causes:

Anaemia, bleeding, CKD

WCC

Normal Range:

4–11 ×10⁹/L

High Causes:

Infection, inflammation, leukaemia

Low Causes:

Aplastic anaemia, chemotherapy, viral infection

Platelets

Normal Range:

150–400 ×10⁹/L

High Causes:

Inflammation, iron deficiency

Low Causes:

ITP, DIC, sepsis

💧

Urea & Electrolytes (U&E)

Renal function and electrolyte balance

Test	Normal Range	High Causes	Low Causes
Sodium (Na⁺)	135–145 mmol/L	Dehydration, SIADH	Diuretics, Addison's, fluid overload
Potassium (K⁺)	3.5–5.0 mmol/L	AKI, ACEi, haemolysis	Diuretics, GI loss, insulin
Urea	2.5–7.8 mmol/L	Renal dysfunction, dehydration, GI bleed	Low protein intake, liver disease
Creatinine	60–110 µmol/L	Renal failure, rhabdomyolysis	Low muscle mass

Sodium (Na⁺)

Normal Range:

135–145 mmol/L

High Causes:

Dehydration, SIADH

Low Causes:

Diuretics, Addison's, fluid overload

Potassium (K⁺)

Normal Range:

3.5–5.0 mmol/L

High Causes:

AKI, ACEi, haemolysis

Low Causes:

Diuretics, GI loss, insulin

Urea

Normal Range:

2.5–7.8 mmol/L

High Causes:

Renal dysfunction, dehydration, GI bleed

Low Causes:

Low protein intake, liver disease

Creatinine

Normal Range:

60–110 µmol/L

High Causes:

Renal failure, rhabdomyolysis

Low Causes:

Low muscle mass

🧪

Liver Function Tests (LFTs)

Hepatic function assessment

Test	Normal Range	High Causes	Low Causes
ALT	<40 IU/L	Hepatitis, alcohol, meds	Not usually significant
ALP	30–130 IU/L	Cholestasis, bone disease	Malnutrition
Bilirubin	<20 µmol/L	Haemolysis, liver disease	Not usually significant
Albumin	35–50 g/L	Dehydration	Liver disease, nephrotic syndrome

ALT

Normal Range:

<40 IU/L

High Causes:

Hepatitis, alcohol, meds

Low Causes:

Not usually significant

ALP

Normal Range:

30–130 IU/L

High Causes:

Cholestasis, bone disease

Low Causes:

Malnutrition

Bilirubin

Normal Range:

<20 µmol/L

High Causes:

Haemolysis, liver disease

Low Causes:

Not usually significant

Albumin

Normal Range:

35–50 g/L

High Causes:

Dehydration

Low Causes:

Liver disease, nephrotic syndrome

🧠

TFT Interpretation Guide

Thyroid function test patterns

Condition	TSH	Free T4	Free T3	Notes
Primary Hypothyroidism	↑	↓	↓ or Normal	Thyroid gland failure
Subclinical Hypothyroidism	↑	Normal	Normal	Early thyroid failure
Primary Hyperthyroidism	↓	↑	↑	Graves', toxic nodules
Subclinical Hyperthyroidism	↓	Normal	Normal	Often early hyperthyroidism
Secondary Hypothyroidism	↓ or Normal	↓	↓	Pituitary dysfunction
Sick Euthyroid	↓ or Normal	↓	↓ or Normal	Non-thyroidal illness

Primary Hypothyroidism

TSH:

↑

Free T4:

↓

Free T3:

↓ or Normal

Notes:

Thyroid gland failure

Subclinical Hypothyroidism

TSH:

↑

Free T4:

Normal

Free T3:

Normal

Notes:

Early thyroid failure

Primary Hyperthyroidism

TSH:

↓

Free T4:

↑

Free T3:

↑

Notes:

Graves', toxic nodules

Subclinical Hyperthyroidism

TSH:

↓

Free T4:

Normal

Free T3:

Normal

Notes:

Often early hyperthyroidism

Secondary Hypothyroidism

TSH:

↓ or Normal

Free T4:

↓

Free T3:

↓

Notes:

Pituitary dysfunction

Sick Euthyroid

TSH:

↓ or Normal

Free T4:

↓

Free T3:

↓ or Normal

Notes:

Non-thyroidal illness

🧬

Tumour Markers

Oncological biomarkers and associations

Marker	Associated Cancer(s)	Notes
AFP	Hepatocellular carcinoma, germ cell tumours	Also raised in liver disease
CEA	Colorectal, pancreatic, gastric, breast	Used for monitoring, not screening
CA 19-9	Pancreatic, biliary tract cancers	May also rise in benign biliary disease
CA 15-3	Breast cancer	Mainly for monitoring recurrence
CA 125	Ovarian cancer	Also raised in benign conditions (e.g. endometriosis)
PSA	Prostate cancer	Screening and monitoring; consider age and DRE
Beta-hCG	Germ cell tumours, choriocarcinoma	Also used in pregnancy testing

AFP

Associated Cancers:

Hepatocellular carcinoma, germ cell tumours

Notes:

Also raised in liver disease

CEA

Associated Cancers:

Colorectal, pancreatic, gastric, breast

Notes:

Used for monitoring, not screening

CA 19-9

Associated Cancers:

Pancreatic, biliary tract cancers

Notes:

May also rise in benign biliary disease

CA 15-3

Associated Cancers:

Breast cancer

Notes:

Mainly for monitoring recurrence

CA 125

Associated Cancers:

Ovarian cancer

Notes:

Also raised in benign conditions (e.g. endometriosis)

PSA

Associated Cancers:

Prostate cancer

Notes:

Screening and monitoring; consider age and DRE

Beta-hCG

Associated Cancers:

Germ cell tumours, choriocarcinoma

Notes:

Also used in pregnancy testing

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