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 emergency services for severe trouble breathing, severe chest pain, fainting, a seizure, sudden confusion, new one-sided weakness, or bleeding that will not stop.
Seek urgent advice for a fever when your team has warned that your blood counts may be low, repeated vomiting, inability to keep fluids down, rapidly increasing swelling, uncontrolled pain, heavy bleeding, or signs of infection around a brachytherapy insertion site.
Contact your radiation team during routine hours about worsening skin changes, persistent nausea, trouble eating, increasing diarrhoea, urinary discomfort, new pain, or fatigue that interferes with daily activities.
These effects may need treatment, but they are not usually emergencies.
And for anyone, someone who:
Every sign above is quoted from the sofidex article on Radiation therapy for cancer. If you are not sure, err upward — it is always reasonable to be checked.