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 if you have difficulty breathing, severe swelling of the mouth or throat, collapse, or another sign of a severe allergic reaction.
These are not usual symptoms of uncomplicated thrush.
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 has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Contact a healthcare service promptly if you have fever, feel generally unwell, cannot keep down fluids, or develop painful or difficult swallowing.
A baby who is feeding poorly or producing fewer wet nappies should also be assessed promptly.
3
Does any of this apply?
Book an appointment
Arrange a routine appointment or ask a pharmacist for advice if this is your first suspected episode, you are unsure whether it is thrush, or over-the-counter treatment is unsuitable for you.
Seek routine medical assessment if:
Symptoms keep returning or do not improve after treatment
You are pregnant or breastfeeding
You have diabetes or a weakened immune system
Oral thrush continues without an obvious cause
You have unusual discharge, sores, bleeding, or significant pain
A baby has mouth patches or feeding difficulties
Every sign above is quoted from the sofidex article on Thrush. If you are not sure, err upward — it is always reasonable to be checked.