Shortness of breath: Red Flags & Emergency Signs
Acute breathlessness can represent immediate life threats including PE, severe asthma, anaphylaxis, or tension pneumothorax — any sudden onset requires urgent evaluation.
If you have this symptom right now
Call 999 (UK) / 112 (EU) / 911 (US) immediately if any emergency warning signs are present. Do not drive yourself. Do not wait to see if it improves.
🚨 Call 999 / 112 Immediately
- ⚠Breathlessness with cyanosis (blue lips or fingertips) — oxygen failure
- ⚠Sudden breathlessness with pleuritic chest pain and tachycardia — possible pulmonary embolism
- ⚠Severe wheeze with stridor and swollen face/lips — anaphylaxis (use adrenaline auto-injector)
- ⚠Breathlessness with inability to speak full sentences — severe asthma attack
- ⚠Sudden breathlessness with absent breath sounds on one side — pneumothorax
- ⚠Breathlessness with frothy pink sputum and lying flat — acute pulmonary oedema
⚡ See a Doctor Today
- •Breathlessness at rest with oxygen saturation below 94% on pulse oximeter
- •Breathlessness worsening over hours in a patient with COPD or asthma
- •Breathlessness in pregnancy (can indicate PE, peripartum cardiomyopathy)
- •Breathlessness with ankle swelling and reduced exercise tolerance (heart failure)
High-Risk Combinations
When shortness of breath occurs together with any of these symptoms, urgency increases significantly:
PE, MI, or tension pneumothorax — 999 immediately
Tachycardia + breathlessness = PE, severe infection, or cardiac compromise
Oxygen saturation crisis — immediate intervention needed
Anaphylaxis — use adrenaline auto-injector and call 999
Breathlessness + fever = possible pneumonia, sepsis, or severe COVID
Conditions to Rule Out Urgently
Wells score + D-dimer + CTPA; sudden onset with pleuritic pain
Allergic trigger; treat with IM adrenaline 0.5mg immediately
CXR; tension pneumothorax = haemodynamic collapse
Pulsus paradoxus; echo; pericardiocentesis
ECG; VT or SVT at high rate causes breathlessness + low output
Flash pulmonary oedema; STEMI/NSTEMI with left ventricular failure
Condition Authority Pages
Differential diagnosis analyses:
Side-by-side comparisons:
When to Call Emergency Services
- →Any sudden onset breathlessness — do not wait
- →Blue lips, fingertips, or tongue (cyanosis)
- →Cannot speak in full sentences due to breathlessness
- →Known anaphylaxis — use auto-injector and call 999 regardless of initial response