Blood Tests for Chest Pain
What the cardiac blood markers mean, which results matter, and when chest pain is an emergency.
If you have chest pain right now, do not read further - call 000.
Chest pain with sweating, breathlessness, jaw/arm/back pain, nausea, dizziness, or pain that lasts more than 10 minutes is a medical emergency. The most dangerous heart attack is the one being slept off. Australian guidelines say: chew an aspirin if you have one, sit down, and call 000 - do not drive yourself.
What Cardiac Blood Tests Actually Tell You
When someone arrives at hospital with chest pain, the medical team is asking three questions at once: is this a heart attack right now, is the heart under chronic strain, and what is the long-term risk of another event? Each question has its own blood test.
Troponin answers question one. BNP answers question two. Cholesterol, HbA1c, kidney function and thyroid answer question three. A normal ECG and a single normal troponin is reassuring; a rising troponin is a heart attack until proven otherwise.
Importantly, a normal troponin does NOT rule out future heart attacks - it rules out heart muscle damage right now. The long-term risk markers are just as important when chest pain settles and you go home with a plan.
The 8 Cardiac Blood Markers Explained
Troponin (hs-cTn)
What it is: Troponin is a protein released into the blood when heart muscle cells are damaged. It is the single most important blood test for diagnosing a heart attack. High-sensitivity troponin (hs-cTn) can detect very small amounts within an hour of injury.
When ordered: Anyone with chest pain, breathlessness, or other suspected cardiac symptoms in the emergency department. Often repeated 1-3 hours later to detect a rising pattern (rising = active heart attack).
How it is interpreted: Below the 99th percentile cutoff means no significant heart muscle damage. Elevated and rising suggests acute myocardial infarction. Elevated but stable can indicate chronic heart strain, myocarditis, kidney disease, or recent heavy exercise.
BNP / NT-proBNP
What it is: B-type natriuretic peptide is released by the heart when the ventricles are stretched - typically because they are working too hard. It is the key marker for heart failure and helps tell whether breathlessness comes from the heart or the lungs.
When ordered: Chest pain plus breathlessness, ankle swelling, or fatigue. Also used to monitor known heart failure patients to track whether their condition is stable.
How it is interpreted: Normal (under ~100 pg/mL BNP, under ~300 pg/mL NT-proBNP) makes heart failure very unlikely. Markedly elevated levels suggest significant cardiac strain and need urgent assessment.
D-dimer
What it is: D-dimer is a fragment released when a blood clot is being broken down. The main use in chest pain is to rule out pulmonary embolism (PE) - a blood clot in the lung - which is a major mimic of a heart attack.
When ordered: Chest pain that is sharp, worse on breathing in, plus risk factors for clots (recent surgery, long flights, oral contraceptive, cancer, immobility, swollen leg).
How it is interpreted: A normal D-dimer in a low-risk patient effectively rules out PE. A raised D-dimer alone is NOT enough to diagnose PE - many things lift it (infection, pregnancy, surgery). It triggers further imaging like a CTPA scan.
CRP / ESR
What it is: Inflammation markers. Useful in chest pain when pericarditis (inflammation of the sac around the heart) or myocarditis is suspected. Both CRP and ESR rise within hours to days of inflammation starting.
When ordered: Sharp central chest pain that gets worse lying flat and better leaning forward, often after a recent viral illness. Or chest pain with fever and a friction rub heard on stethoscope.
How it is interpreted: Markedly elevated CRP with a typical pain pattern strongly supports pericarditis. Used together with ECG changes and an echocardiogram.
Cholesterol Panel
What it is: Total cholesterol, LDL, HDL, triglycerides, non-HDL. These are not used to diagnose acute chest pain but they map your long-term risk of coronary artery disease - which underpins most heart attacks.
When ordered: After a cardiac event (to guide medication), as part of an annual heart health check, or when chest pain is suspected to be exertional angina from narrowed arteries.
How it is interpreted: LDL under 1.8 mmol/L is the target for anyone with known coronary disease. HDL above 1.0 (men) / 1.3 (women) is protective. Triglycerides under 1.7 mmol/L. Non-HDL gives a simple overall risk picture.
HbA1c & Fasting Glucose
What it is: Diabetes massively increases the risk of coronary heart disease and is often the reason chest pain develops in someone in their 40s and 50s. HbA1c reflects 3-month average blood sugar.
When ordered: Always after a cardiac event. Routinely as part of any cardiac risk assessment, even if you have no symptoms of diabetes.
How it is interpreted: HbA1c under 5.7% is normal, 5.7-6.4% is prediabetes, 6.5%+ is diabetes. A new diagnosis at the time of chest pain is unfortunately common.
TSH (Thyroid)
What it is: An overactive thyroid (hyperthyroidism) is a classic cause of palpitations and atypical chest discomfort. It is also a treatable trigger for atrial fibrillation, which can mimic cardiac chest pain.
When ordered: Chest pain or pounding heart, especially with weight loss, heat intolerance, tremor, or anxiety.
How it is interpreted: Suppressed TSH (very low) with high T4/T3 confirms hyperthyroidism. Treatment of the thyroid usually settles the cardiac symptoms.
Electrolytes & Magnesium
What it is: Potassium, sodium and magnesium directly affect the electrical activity of the heart. Imbalances can trigger arrhythmias that feel like chest pain or palpitations.
When ordered: Chest pain plus palpitations, after vomiting / diarrhoea, in people on diuretics, or anyone admitted to ED with a cardiac picture.
How it is interpreted: Low potassium or magnesium can be life-threatening when severe - they are corrected promptly in hospital. Often a missed cause of recurrent palpitations.
Not Every Chest Pain Is Cardiac
Roughly half of chest pain in primary care turns out to be non-cardiac. Blood tests are still useful - they help rule the heart OUT, which is a powerful answer in itself.
| Non-cardiac cause | Typical pattern | Useful blood tests |
|---|---|---|
| Reflux / GORD | Burning chest pain, worse lying down or after meals. Blood tests are usually normal but FBC may show iron deficiency from chronic reflux bleeding. | FBC, Ferritin, H. pylori serology |
| Anxiety / Panic | Sudden chest tightness, racing heart, hyperventilation. Blood tests rule out thyroid, cardiac, and electrolyte causes first - never diagnose anxiety until those are normal. | Troponin, TSH, Electrolytes |
| Musculoskeletal | Costochondritis, intercostal strain - reproducible by pressing the chest wall. Blood tests are normal; inflammation markers may be slightly raised. | CRP, ESR |
| Pleurisy / Lung infection | Sharp pain on breathing in, fever, cough. FBC and CRP elevated; chest x-ray confirms. | FBC, CRP, Procalcitonin |
| Anaemia | Chest tightness on exertion, breathlessness, dizziness. Severe anaemia mimics angina because the heart works harder to deliver oxygen. | FBC, Ferritin, Iron studies |
Long-Term Heart Health Monitoring
If you have had chest pain investigated and the heart attack has been excluded, the next conversation is about prevention. Your GP should be ordering a structured cardiovascular risk panel every 1-2 years.
Total / HDL / LDL Cholesterol
Triglycerides
Non-HDL cholesterol
HbA1c
Fasting glucose
eGFR + creatinine
Urine albumin:creatinine ratio
TSH
Full Blood Count
hs-CRP (long-term cardiac risk)
Chest Pain Emergency Signs - Call 000
Track Your Cardiac Markers Over Time
Upload past cardiac and cholesterol results - SmarterBlood charts how your heart-health markers change over time so you can spot trends, not just single values.