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 sudden severe testicular pain, especially with swelling or nausea.
Get emergency help if you cannot pass urine, have had a major pelvic or genital injury, or have heavy bleeding with weakness, faintness, or dizziness.
Without these features, blood in the semen does not usually require emergency care.
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
Seek same-day medical care if blood in the semen occurs with:
Fever or chills
Pelvic, lower abdominal, or testicular pain
Difficulty passing urine
Increasing swelling or redness of the scrotum
3
Does any of this apply?
Book an appointment
Arrange a routine appointment for unexplained blood in the semen, particularly if it happens more than once, continues for several weeks, or first occurs after age 40.
Also seek advice for pain during ejaculation, burning when urinating, genital discharge, a testicular lump, or blood in your urine.
Every sign above is quoted from the sofidex article on Blood in the semen. If you are not sure, err upward — it is always reasonable to be checked.