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 help for:
Sudden or severe difficulty breathing
Blue or grey lips or skin
Fainting, severe confusion, or difficulty staying awake
New severe chest pressure or chest pain
Coughing up more than a small streak of blood
These symptoms can have causes other than pleural effusion, including a blood clot, heart problem, severe infection, or collapsed lung.
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
Ask for prompt medical assessment if breathlessness is worsening, breathing becomes painful, or you develop fever, shaking chills, or a productive cough.
New swelling of the legs or rapid fluid-related weight gain also deserves timely review.
After thoracentesis or chest-tube treatment, get urgent advice for increasing breathlessness, severe chest pain, fever, bleeding, or redness and drainage around the procedure site.
3
Does any of this apply?
Book an appointment
Routine follow-up is appropriate when symptoms are stable but not improving, the effusion has returned before, or a planned scan or test result needs review.
Every sign above is quoted from the sofidex article on Pleural effusion. If you are not sure, err upward — it is always reasonable to be checked.