Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services now if you have:
Severe or rapidly worsening difficulty breathing
Trouble speaking more than a few words
Blue, grey, or unusually pale lips or skin
Chest pressure, fainting, confusion, or marked drowsiness
Sudden breathlessness with coughing up blood
Swelling of the lips or tongue, hives, or throat tightness
Breathlessness after choking or a serious injury
Move into fresh air and call emergency services if several people in the same building develop headache, dizziness, nausea, or breathlessness.
This may suggest carbon monoxide exposure.
Do not re-enter the building until it has been declared safe.
And for anyone, someone who:
is struggling to breathe, gasping, choking, or cannot get words out
has lips or skin that look pale, blue, grey or blotchy
Other emergency signs, for anyone
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek same-day medical advice for new breathlessness at rest, a clear worsening of an existing breathing problem, or symptoms that are not responding to your prescribed treatment.
Fever with increasing breathlessness also needs prompt assessment.
And for anyone, someone who:
is getting rapidly more short of breath, or has gained several pounds in a few days with swelling
3
Does any of this apply?
Book an appointment
Book a routine appointment if breathlessness keeps returning, lasts longer than expected after an illness, wakes you at night, or limits walking and other usual activities.
And for anyone, someone who:
is more tired or breathless than usual doing things they used to manage
Every sign above is quoted from the sofidex article on Breathing problems. If you are not sure, err upward — it is always reasonable to be checked.