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 care for:
Chest pain
Fainting or being difficult to wake
Severe breathlessness or breathlessness at rest
Confusion
Blue or grey lips
Signs of a serious transfusion reaction, such as fever, chills, back pain, breathing difficulty, or dark urine during or soon after a transfusion
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
Arrange a routine or prompt appointment if you develop ongoing tiredness, mild breathlessness, yellowing of the eyes, dark urine, or reduced exercise tolerance.
Contact your care team if known symptoms return after improving or if treatment side effects are affecting daily life.
Seek same-day medical advice for rapidly worsening weakness, a new fast heartbeat, much darker urine, increasing jaundice, or breathlessness with light activity.
These changes may mean hemolysis or anemia is becoming more active.
The article also says
Do not drive yourself if you feel faint, confused, or severely short of breath.
Every sign above is quoted from the sofidex article on Immune hemolytic anemia. If you are not sure, err upward — it is always reasonable to be checked.