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 rapid breathing comes with:
Severe difficulty breathing or inability to speak in full sentences
Blue, grey, or unusually pale lips, tongue, or skin
New confusion, fainting, extreme drowsiness, or difficulty waking
Sudden chest pain, especially with sweating, nausea, or faintness
Choking or swelling of the lips, tongue, face, or throat
A suspected overdose, poisoning, or serious chest injury
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 urgent same-day medical care for new rapid breathing at rest, breathing that is getting worse, or breathlessness with fever and significant illness.
Prompt assessment is also important for coughing up blood, one-sided leg swelling, new wheezing, or signs of dehydration such as very little urine.
Babies and young children should be assessed urgently if breathing is persistently fast or laboured, especially with poor feeding, grunting, ribs pulling inward, unusual sleepiness, or a change in colour.
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 episodes keep returning, have no clear trigger, disturb sleep, or reduce your usual activity.
Mention any cough, wheezing, weight change, heavy menstrual bleeding, or symptoms that occur when lying flat.
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 Rapid shallow breathing. If you are not sure, err upward — it is always reasonable to be checked.