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 for:
Sudden breathlessness, chest pain, coughing up blood, or fainting
Bleeding from a leg vein that does not stop with firm pressure
Severe illness, confusion, or collapse alongside a red or infected leg
Get emergency help if bleeding is heavy or continues.
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 for sudden swelling or pain in one leg, especially if it is warm, red, or tender.
These can be symptoms of DVT.
Rapidly spreading redness, worsening ulcer pain, pus, or fever may suggest infection and also needs prompt assessment.
3
Does any of this apply?
Book an appointment
Arrange a routine appointment if you have persistent leg swelling, heaviness, visible varicose veins with symptoms, brown or inflamed skin, or a sore that is not healing.
Earlier assessment may help prevent further skin damage.
The article also says
If a varicose vein bleeds, lie down, raise the leg, and press firmly over the bleeding point with a clean cloth or dressing.
Every sign above is quoted from the sofidex article on Venous insufficiency. If you are not sure, err upward — it is always reasonable to be checked.