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 sudden heavy sweating occurs with chest pressure or pain, severe breathing difficulty, fainting, marked weakness, or confusion.
These symptoms may signal a serious heart or circulation problem.
Move to a cooler place and seek emergency help.
Seek emergency help if you cannot swallow safely, lose consciousness, or do not recover.
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
Do not wait for the person to stop sweating.
3
Does any of this apply?
Book an appointment
Arrange a routine medical appointment if sweating:
Starts without a clear reason or becomes noticeably heavier
Regularly wakes you or soaks your bedding
Interferes with work, sleep, relationships, or everyday activities
Occurs with ongoing fever, unexplained weight loss, a racing heartbeat, or persistent cough
Began after starting or changing a medicine
Causes repeated rashes, broken skin, or infections
The article also says
Confusion, collapse, seizures, or very high body temperature during hot weather or exercise can indicate heatstroke.
If you have diabetes, sweating with shaking, hunger, dizziness, or confusion may mean low blood sugar.
Follow your personal low-blood-sugar plan.
Every sign above is quoted from the sofidex article on Sweating. If you are not sure, err upward — it is always reasonable to be checked.