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
Get urgent or emergency help for:
Chest pain or pressure
Severe difficulty breathing, especially at rest
Fainting or being difficult to wake
A very fast heartbeat with weakness or dizziness
Rapidly worsening weakness, confusion, or inability to walk safely
Sudden weakness on one side, facial drooping, or difficulty speaking may be a stroke rather than vitamin B12 deficiency and requires emergency help.
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 prompt medical assessment for new tingling, numbness, weakness, memory changes, vision changes, or problems with balance.
These symptoms are not always caused by vitamin B12 deficiency, but they should not be ignored.
3
Does any of this apply?
Book an appointment
Arrange a routine medical appointment if you have persistent tiredness, breathlessness during activity, a sore tongue, unexplained appetite or weight changes, or risk factors for vitamin B12 deficiency.
Every sign above is quoted from the sofidex article on Vitamin B12 deficiency anemia. If you are not sure, err upward — it is always reasonable to be checked.