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 a slow heart rate occurs with:
Fainting, collapse, or difficulty waking
Severe trouble breathing
New or severe chest pain
Sudden confusion
Pale, blue, grey, or very sweaty skin
No normal breathing or no detectable pulse
And for anyone, someone who:
has chest pain, tightness or pressure lasting more than a few minutes
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
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 same-day medical advice if a slow pulse is new and comes with dizziness, unusual weakness, shortness of breath, near-fainting, or reduced ability to do normal activities.
An awake heart rate that repeatedly stays below 40 and is not normal for you also needs prompt assessment.
And for anyone, someone who:
is getting rapidly more short of breath, or has gained several pounds in a few days with swelling
3
Does any of this apply?
Book an appointment
Book a routine appointment if readings are repeatedly slower than usual but you otherwise feel well.
Arrange follow-up if symptoms are mild but keep returning, or if a medicine may be affecting your heart rate.
The article also says
If someone is unresponsive and not breathing normally, begin CPR if you can and use an automated external defibrillator if one is available.
Every sign above is quoted from the sofidex article on Slow heart rate. If you are not sure, err upward — it is always reasonable to be checked.