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 your tongue is rapidly swelling or you have trouble breathing, swallowing, or speaking.
Also seek emergency help for tongue swelling with facial swelling, widespread hives, faintness, or a feeling that your throat is closing.
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
Arrange same-day medical or dental advice if you have painful swelling, fever, pus, worsening neck or facial swelling, or difficulty drinking enough fluid.
These features can suggest an infection or another problem requiring prompt assessment.
And for anyone, someone who:
has a fever with a stiff neck, a rash that does not fade under pressure, or severe headache
3
Does any of this apply?
Book an appointment
Book a routine appointment with a doctor or dentist if:
A patch, ulcer, or lump remains in the same place for three weeks
The area repeatedly bleeds or becomes increasingly painful
Eating, drinking, or brushing your teeth is difficult
You have unexplained weight loss or a persistent neck lump
A white coating does not gently wipe away
You are unsure whether the patches are actually moving
Symptoms keep returning and self-care is not enough
This may help at your appointment.
The article also says
Taking clear photographs every few days can show whether the pattern is changing.
Every sign above is quoted from the sofidex article on Wandering rash tongue. If you are not sure, err upward — it is always reasonable to be checked.