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 excessive thirst occurs with confusion, fainting, a seizure, severe breathing difficulty, or difficulty waking.
Rapid, deep breathing with vomiting, abdominal pain, marked drowsiness, or fruity-smelling breath can indicate a serious blood sugar problem.
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
Seek urgent, same-day medical care if:
You cannot keep fluids down
You are very dizzy when standing or are passing very little urine
New intense thirst occurs with frequent urination, vomiting, or severe weakness
A child develops marked thirst, frequent urination, new bed-wetting, or weight loss
3
Does any of this apply?
Book an appointment
Book a routine appointment if thirst persists for several days despite drinking normally, repeatedly wakes you, or occurs with frequent urination.
Arrange follow-up if it began after a new medicine or dose change.
The article also says
If you have been told to limit fluids because of heart, kidney, or liver disease, follow your existing plan and contact your healthcare team rather than increasing fluids yourself.
Every sign above is quoted from the sofidex article on Excessive thirst. If you are not sure, err upward — it is always reasonable to be checked.