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Blood Test Interpretation

⚠️ Important: Reference ranges below are adapted from general clinical education guidelines (Clinpath, SA Pathology). Ranges vary between pathology labs and can differ by patient age, sex, and clinical context. Always interpret results alongside your facility's specific reference intervals and in the context of the patient's full clinical picture. When in doubt — escalate to your supervising nurse or team.

Tip: When interpreting bloods, always consider the trend (is it improving or deteriorating?) alongside the absolute value.

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Full Blood Count (FBC) — Haematology

FBC

Test	Units	Reference Range
Haemoglobin (Hb)	g/L	119 – 160
Red Cell Count	×10¹²/L	3.8 – 5.8
Haematocrit (HCT)	—	0.35 – 0.48
MCV	fL	80 – 100
MCH	pg	27.0 – 32.0
MCHC	g/L	310 – 360
RDW	—	10.0 – 15.0
White Cell Count (WCC)	×10⁹/L	4.0 – 11.0
Neutrophils	×10⁹/L	1.7 – 7.5
Lymphocytes	×10⁹/L	1.0 – 4.0
Monocytes	×10⁹/L	0.0 – 1.0
Eosinophils	×10⁹/L	0.0 – 0.5
Basophils	×10⁹/L	0.0 – 0.3
Platelets	×10⁹/L	150 – 450

🔎 Clinical Interpretation Tips

Haemoglobin <100 g/L is concerning — consider transfusion if symptomatic. Investigate the cause: GI bleeding (gastric ulcer, large bowel), renal or bone marrow dysfunction. Review anticoagulant orders.

White Cell Count ↑ High → infection or inflammatory response (also order CRP). ↓ Low → immunocompromised (handle with care re: infection risk).

Platelets ↓ Low (<150) → ↑ bleeding risk; flag before invasive procedures. ↑ High (>450) → may indicate clotting risk or inflammatory response.

⚗️

Biochemistry Panel

EUC / LFT

Electrolytes

Test	Units	Reference Range
Sodium (Na⁺)	mmol/L	135 – 145
Potassium (K⁺)	mmol/L	3.5 – 5.5
Chloride (Cl⁻)	mmol/L	95 – 110
Bicarbonate (HCO₃⁻)	mmol/L	20 – 32

🔎 Interpretation

Sodium ↓ Hyponatraemia — can cause confusion; may need fluid restriction. Investigate cause (SIADH, diuretics, vomiting).

Potassium ↕ Out of range = cardiac arrhythmia risk — priority correction. ↓ Low: treat with IV KCl mini-bags, oral Slow-K or Chlorvescent. ↑ High: insulin/glucose infusion or Resonium. May be altered by refeeding syndrome.

Renal Function

Test	Units	Reference Range
Urea	mmol/L	2.5 – 7.0
Creatinine	µmol/L	45 – 85
eGFR	mL/min	> 59
Uric Acid	mmol/L	0.15 – 0.40

🔎 Interpretation

Elevated Cr / ↓ eGFR Impaired renal function — may be due to dehydration or nephrotoxic medications. Treat with fluids and/or hold/reduce nephrotoxic drugs (e.g. NSAIDs, certain antibiotics).

Rhabdomyolysis If CK (creatine kinase) is significantly elevated → risk of acute kidney injury. Monitor closely.

Liver Function Tests (LFT)

Test	Units	Reference Range
Total Bilirubin	µmol/L	3 – 15
Alkaline Phosphatase (ALP)	U/L	20 – 105
Gamma-GT (GGT)	U/L	5 – 35
LDH	U/L	120 – 250
AST	U/L	10 – 35
ALT	U/L	5 – 30
Total Protein	g/L	68 – 85
Albumin	g/L	37 – 48
Globulin	g/L	23 – 39
Cholesterol	mmol/L	3.5 – 5.5
Glucose (random)	mmol/L	3.6 – 7.8

🔎 Interpretation

Elevated LFTs May be medication-induced (e.g. paracetamol, statins, certain antibiotics). If LFTs are deranged, review and consider holding hepatotoxic medications. Escalate to medical team.

Low Albumin Indicates malnutrition, chronic illness, or liver disease. Affects drug binding — can alter medication levels in the body.

Other Biochemistry Markers

Test	Units	Reference Range
Calcium	mmol/L	2.10 – 2.60
Corrected Calcium	mmol/L	2.10 – 2.60
Phosphate	mmol/L	0.7 – 1.5

Calcium and phosphate may be altered in refeeding syndrome, malnutrition, or renal disease.

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Coagulation

COAGS

Test	Full Name	Reference Range	Clinical Use
APTT	Activated Partial Thromboplastin Time	25 – 38 sec	General test of blood thickness; guides heparin infusion dosing
INR	International Normalised Ratio	0.8 – 1.2 (therapeutic: 2–3)	Used when patient is on warfarin. Goal 2–3 depending on indication. If too high → give Vitamin K to reverse.
Fibrinogen	Clotting protein from liver	1.5 – 4.0 g/L	Low fibrinogen → ↑ bleeding risk (needed to form clots)

🔎 Key Points

INR on Warfarin Therapeutic goal is usually 2–3 (higher for mechanical heart valves). INR >4 → significant bleeding risk. If supratherapeutic and bleeding: give IV Vitamin K or fresh frozen plasma (FFP) as directed.

APTT on Heparin Therapeutic APTT goal is typically 60–100 sec (1.5–2.5× normal). Check your facility's heparin infusion protocol for target range.

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Cardiac Markers

CARDIAC

Bloods are a key indicator of cardiac recovery, deterioration, or diagnosis.

Test	Normal / Threshold	Elevated Indicates	Notes
Troponin	< 16 ng/L	Cardiac muscle distress (e.g. ischaemia, MI)	"Serial trops" preferred: on admission, 6–8 hrs post, ± next day
Pro-BNP	<125 ng/L (<75yo) <450 ng/L (>75yo)	Heart failure / fluid overload	Useful for diagnosing and monitoring CCF / HFrEF
D-Dimer	< 0.5 mg/L	Clot formation (DVT or PE)	Sensitive but not specific — elevated in many conditions incl. infection, pregnancy, post-op
CRP	< 5 mg/L	Infection or systemic inflammation	Used alongside WCC to assess infection response

🔎 Clinical Notes

Rising Troponin Suggests ongoing myocardial injury. Always assess in series — a single elevated troponin is less informative than an upward trend. Notify the medical team promptly.

D-Dimer Limits A negative D-Dimer helps rule out PE/DVT in low-risk patients. A positive result needs further imaging (CTPA or ultrasound) — it does not confirm a clot on its own.

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Arterial Blood Gas (ABG)

ABG

ABG provides an immediate snapshot of respiratory and metabolic status. Used in emergencies (MET calls), respiratory distress, or to assess home oxygen needs.

Parameter	Reference Range
pH	7.35 – 7.45
pCO₂	35 – 48 mmHg
pO₂	83 – 108 mmHg
HCO₃⁻ (calc)	22 – 28 mmol/L
Base Excess	−3 to +3
O₂ Saturation	95 – 100%
Sodium	135 – 145 mmol/L
Potassium	3.5 – 5.5 mmol/L
Chloride	95 – 110 mmol/L
Ionised Calcium	1.15 – 1.30 mmol/L
Creatinine	60 – 115 µmol/L
Glucose (random)	3.6 – 7.8 mmol/L
Lactate	0.5 – 2.2 mmol/L

⚡ Quick ABG Interpretation — 4 Steps

Check pH
<7.35 = Acidosis | >7.45 = Alkalosis

Check pCO₂ (respiratory driver)
↑ pCO₂ + acidosis = Respiratory Acidosis
↓ pCO₂ + alkalosis = Respiratory Alkalosis

Check HCO₃⁻ (metabolic driver)
↓ HCO₃⁻ + acidosis = Metabolic Acidosis
↑ HCO₃⁻ + alkalosis = Metabolic Alkalosis

Is it compensated?
If both pCO₂ & HCO₃⁻ are abnormal → body is compensating.
pH still abnormal = partially compensated.
pH normal = fully compensated.

🔎 Key Tips

Lactate ↑ Elevated lactate (>2.2 mmol/L) indicates tissue hypoperfusion or hypoxia — a key sepsis marker. >4 = severe; escalate immediately.

pO₂ ↓ Hypoxaemia — assess SpO₂, work of breathing, and oxygen delivery. Consider increasing O₂ therapy and escalating if persistent.

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Cognitive Impairment Screening — Bloods to Order

When assessing a patient for cognitive impairment (e.g. delirium workup), bloods are used to rule out treatable organic causes.

Standard bloods to request:

📌 HbA1c 📌 Lipids / Cholesterol 📌 Thyroid Function Tests (TFTs) 📌 Vitamin B12 & Folate 📌 Syphilis serology 📌 Iron studies 📌 Vitamin D 📌 Calcium 📌 LFT (Liver Function) 📌 EUC (Electrolytes, Urea, Creatinine) 📌 FBC (Full Blood Count) 📌 Urine MC+S (rule out UTI)

These tests help rule out organic causes of cognitive change. Many older patients have dietary deficiencies that contribute to cognitive impairment — correcting these with supplements may improve function. Always also consider UTI as a common reversible cause of acute confusion in older adults.

Blood Test Interpretation Guide for Australian Nursing Students

This page provides a concise blood test interpretation guide for Australian nursing students and new graduate nurses. It covers Full Blood Count (FBC/haematology) including haemoglobin, white cell count and platelets; biochemistry panels including electrolytes (sodium, potassium), renal function (urea, creatinine, eGFR), and liver function tests (ALP, GGT, AST, ALT, albumin); coagulation (INR for warfarin, APTT for heparin, fibrinogen); cardiac markers (troponin, Pro-BNP, D-dimer, CRP); arterial blood gas (ABG) interpretation with a 4-step guide; and a cognitive impairment screening blood panel. Reference ranges are adapted from Clinpath (SA Pathology) general guidelines — always verify with your facility's lab.