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:
Suddenly cannot stand or walk
Develop rapidly increasing weakness
Lose bladder or bowel control with numbness around the groin
Have severe confusion, collapse, or difficulty breathing
Develop sudden facial drooping, one-sided weakness, or speech difficulty
Sudden one-sided symptoms are not typical of subacute combined degeneration and may indicate a stroke or another emergency.
And for anyone, someone who:
is bleeding heavily and it will not stop with firm pressure
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 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 prompt medical assessment if you develop new tingling, numbness, poor balance, leg stiffness, weakness, or difficulty walking.
This is particularly important if symptoms affect both sides, are spreading, or occur after nitrous oxide exposure.
Seek urgent same-day care if weakness or walking difficulty is worsening quickly, or if you develop new problems with bladder or bowel control.
And for anyone, someone who:
has a wound that is hot, spreading red, or leaking pus
3
Does any of this apply?
Book an appointment
Routine follow-up is appropriate for monitoring recovery, reviewing vitamin B12 replacement, checking an ongoing absorption problem, and discussing persistent symptoms that are stable rather than rapidly worsening.
Every sign above is quoted from the sofidex article on Subacute combined degeneration. If you are not sure, err upward — it is always reasonable to be checked.