When to Go to A&E: 20 Medical Red Flags

When to Go to A&E: 20 Medical Red Flags 

In a medical emergency, every second counts. Knowing whether to call 999 (911) or wait for a GP appointment can be life-saving.

If you or someone you are with experiences any of the following ‘Red Flag’ symptoms, you should attend an Accident & Emergency (A&E) department (ER) or call 999 (911) immediately.

Cardiac and respiratory

1. Chest Pain

Potential Causes: Heart attack, Pulmonary Embolism (PE; blood clot in the lung), or Aortic Dissection.

• A&E if: The pain is heavy, tight, or crushing, or if it spreads to your jaw, neck, back, or left arm.

2. Severe Shortness of Breath

Potential Causes: Acute asthma attack, COPD flare-up, heart failure, or pneumonia.

• A&E if: You are struggling to speak in full sentences or your lips are turning blue.

Neurological

3. One-Sided Weakness (FAST)

Potential Causes: Stroke (CVA) or Transient Ischaemic Attack (TIA).

• A&E if: You notice sudden weakness in one arm or leg, or one side of the face is drooping.

4. Difficulty Speaking

Potential Causes: Stroke or neurological emergency.

• A&E if: Speech is slurred, garbled, or the person cannot understand what you are saying.

5. Rapid (New) Confusion or Delirium

Potential Causes: Sepsis, severe infection, medication issue, stroke, or diabetic crisis.

• A&E if: A person who is not normally confused, becomes suddenly agitated, confused, or doesn’t know where they are.

6. Rapid Loss of Vision or Severe Headache

Potential Causes: Meningitis, brain haemorrhage (Subarachnoid Haemorrhage), encephalitis, or acute glaucoma.

• • A&E if: You experience a “thunderclap” headache (the worst pain of your life) or sudden blindness.

7. Seizures

Potential Causes: Epilepsy, head injury, or high fever.

• A&E if: A seizure lasts longer than 5 minutes or it is the person’s first seizure.

8. Unexplained Drowsiness

Potential Causes: Overdose, head injury, severe infection or metabolic causes

• A&E if: You cannot keep the person awake.

Neurosurgical

9. Severe Back Pain

Potential Causes: Cauda Equina Syndrome (spinal cord compression).

• A&E if: You have back pain combined with numbness in your “saddle area” or changes in your bladder/bowel habits.

Surgical

10. New, Severe Abdominal Pain

Potential Causes: Appendicitis, ectopic pregnancy, perforated ulcer, or bowel obstruction.

• A&E if: The pain is so severe you cannot stand up, is worse on moving or find a comfortable position.

11. Heavy or Uncontrolled Bleeding

Potential Causes: Major trauma, internal bleeding (including gynaecological causes and pregnancy), or complications from surgery.

• A&E if: You are coughing up or vomiting blood, passing it PV or PR, or if a wound will not stop bleeding after 10 minutes of firm pressure.

Other

12. Signs of Sepsis (Infection)

Potential Causes: Severe pneumonia, UTI, or cellulitis.

• A&E if: You have a very high or very low temperature, shivering, no urine output for a day, or mottled/blue skin.

13. Collapse or Fainting

Potential Causes: Heart rhythm problems, severe dehydration, or a fractured hip (common in the elderly).

• A&E if: The person cannot get back up or remains drowsy after waking.

14. Severe Allergic Reaction (Anaphylaxis)

Potential Causes: Nut, bee sting, or medication allergy.

• A&E if: You notice swelling of the lips/tongue or a “tight” throat.

15. Suicide Attempt or Self-Harm

Potential Causes: Mental health crisis.

• A&E if: You have taken an overdose or have an injury from self-harm that requires medical attention.

16. Poisoning

Potential Causes: Accidental ingestion of chemicals or harmful substances.

ENT

17. Choking

Potential Causes: Foreign body airway obstruction.

• A&E if: The person cannot breathe, cough, or speak.

Trauma and orthopaedics

18. Major Trauma

Potential Causes: Road traffic accidents (RTA), falls from height, or serious assault.

19. Severe Burns

Potential Causes: Fire, chemicals, or electricity.

• A&E if: The burn is larger than your hand, involves the face/eyes, or the skin looks charred or white.

20. Suspected Fractures

Potential Causes: Broken limbs or hips.

• A&E if: The limb is at an odd angle, the bone is visible, or the person cannot bear weight.

Summary: 999 (911) or A&E (ER)?

If the person is unconscious, not breathing, or having a fit, call 999 immediately.

If they are conscious but have any of the symptoms above, go to your nearest Accident & Emergency department (ER).

For non-life-threatening symptoms, consider calling NHS 111 (in the UK) for advice on the best service for your needs.