Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call your local emergency number now if you have new, severe, or unexplained chest pressure, tightness, squeezing, or heaviness.
Do the same if chest discomfort occurs at rest, is getting worse, or comes with breathlessness, sweating, nausea, faintness, or pain spreading to the arm, jaw, back, or shoulder.
Emergency medical teams can begin assessment and treatment on the way.
If an emergency call handler advises you to take aspirin, follow that instruction, but mention any aspirin allergy, recent major bleeding, or advice that you must avoid it.
If you already have prescribed medicine for angina, follow the emergency instructions in your personal care plan.
Symptoms that do not settle as expected still require emergency help.
Contact your usual healthcare service promptly, but not as a substitute for emergency care, if previously stable exertional symptoms are gradually becoming more frequent or easier to trigger.
And for anyone, someone who:
Routine follow-up is appropriate for medicine questions, mild side effects, rehabilitation planning, and risk-factor reviews when you are otherwise well.
The article also says
Do not drive yourself to hospital.
Every sign above is quoted from the sofidex article on Unstable angina. If you are not sure, err upward — it is always reasonable to be checked.