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
Seek emergency medical care for severe trouble breathing, blue or gray lips or face, persistent chest pain or pressure, new confusion, a seizure, inability to wake or stay awake, or another sudden and severe change.
Children with severe breathing difficulty, pauses in breathing, unusual limpness, or bluish skin also need emergency care.
And for anyone, someone who:
has lips or skin that look pale, blue, grey or blotchy
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
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
Contact a healthcare professional promptly if:
Fever lasts more than four days.
Symptoms continue for more than about 10 days without improvement.
Symptoms improve and then become worse again.
Breathing is faster, noisier, or more difficult than usual.
There are signs of dehydration, such as very little urine, a dry mouth, or difficulty keeping fluids down.
Asthma, heart disease, lung disease, or another long-term condition is getting worse.
A person with a weakened immune system develops respiratory symptoms.
A baby younger than 3 months has a temperature of 100.4°F (38°C) or higher.
3
Does any of this apply?
Book an appointment
Routine follow-up is usually unnecessary when symptoms are mild and steadily improving.
Continue supportive care and watch for changes.
Consider testing for COVID-19 or influenza based on local public health advice, recent exposure, and personal risk factors.
Return to routine activities as symptoms improve, while continuing steps such as hand hygiene, ventilation, covering coughs, and masking when appropriate.
The article also says
While sick, limit close contact with others, especially people at higher risk.
Stay home when feverish or too unwell for usual activities.
Every sign above is quoted from the sofidex article on Common cold. If you are not sure, err upward — it is always reasonable to be checked.