Call emergency services immediately if breathlessness is:
- Sudden and severe with no obvious cause
- Associated with chest pain, palpitations or collapse
- With coughing blood
- With severe leg pain or swelling (possible PE from DVT)
- In someone with known heart disease
Blood tests for shortness of breath
| Test | What it checks for | Key result |
|---|---|---|
| BNP / NT-proBNP | Heart failure | >400 pg/mL BNP strongly suggests heart failure |
| Troponin | Heart attack (myocardial injury) | Rise/fall pattern = acute MI |
| D-Dimer | Pulmonary embolism (blood clot in lungs) | Negative = PE very unlikely in low-risk patient |
| CBC (haemoglobin) | Anaemia causing breathlessness | Hb <10 g/dL can cause breathlessness at rest |
| CRP / procalcitonin | Pneumonia, infection | Elevated in bacterial lung infection |
| ABG (arterial blood gas) | Oxygen and CO2 levels, acid-base | Low O2, high CO2 = respiratory failure |
| Peak flow / spirometry | Asthma, COPD (not blood tests) | FEV1/FVC <0.7 = obstructive pattern |
Common causes of shortness of breath
Heart failure
The heart cannot pump blood forward efficiently, causing fluid backup in the lungs (pulmonary oedema). Breathlessness is worse lying flat (orthopnoea) and at night (paroxysmal nocturnal dyspnoea). BNP/NT-proBNP is markedly elevated. Treated with diuretics, ACE inhibitors, beta-blockers.
Pulmonary embolism (PE)
Blood clot in the lung arteries causes sudden breathlessness, pleuritic chest pain (sharp, worse on breathing), rapid heart rate and sometimes haemoptysis (coughing blood). D-Dimer is elevated. CT pulmonary angiogram (CTPA) confirms. Treated with anticoagulants (blood thinners).
Pneumonia
Bacterial lung infection causing breathlessness, fever, productive cough and pleuritic pain. CRP and procalcitonin elevated; WBC raised. Chest X-ray shows consolidation. Treated with antibiotics.
Asthma / COPD
Asthma: episodic breathlessness, wheeze and cough. COPD: progressive breathlessness in smokers with chronic cough. Blood tests often normal. Spirometry (lung function test) is key. Treated with inhalers.
Anaemia
Severe anaemia (<8 g/dL haemoglobin) causes breathlessness at rest as the blood cannot carry enough oxygen. The heart compensates by beating faster. CBC is diagnostic. Treat the underlying cause of anaemia.
Anxiety / panic disorder
Anxiety-induced hyperventilation causes breathlessness, tingling in hands/face, chest tightness and dizziness. All cardiac and pulmonary tests normal. Important to rule out organic causes first.
Questions to ask your doctor
- Is my shortness of breath from my heart or my lungs?
- What is my BNP level?
- Do I need a D-dimer or CTPA for a possible pulmonary embolism?
- Do I need spirometry (lung function tests)?
- Should I have a chest X-ray and ECG?