Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency help for:
These symptoms can indicate pressure on an airway or spinal cord, serious infection, or another condition needing immediate care.
If you have follicular lymphoma, contact your lymphoma team promptly about changes between visits.
A rapidly growing node, new pain in a node, or new B symptoms may need earlier testing.
Contact your treatment service urgently for fever, shaking chills, a worsening cough, painful urination, or feeling suddenly unwell.
Do not wait for your next routine appointment.
Arrange a routine medical appointment for a painless lump that persists or enlarges.
Also seek assessment for unexplained weight loss, repeated night sweats, persistent fever, unusual tiredness, or frequent infections.
The article also says
During treatment, follow the instructions you have been given about fever and infection.
Every sign above is quoted from the sofidex article on Follicular lymphoma. If you are not sure, err upward — it is always reasonable to be checked.