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 breathlessness at rest, blue or grey lips, confusion, fainting, crushing chest pain, or an inability to speak normally because of breathing difficulty.
Seek urgent same-day assessment for a clear and rapid change in breathing, fever with worsening respiratory symptoms, new chest discomfort, coughing up blood, or oxygen readings that remain below your advised target.
Arrange a routine or earlier medical review for gradually worsening breathlessness, a persistent increase in cough, lower exercise tolerance, unexplained weight loss, or new medicine side effects.
Mention new joint, muscle, skin, or circulation symptoms because they may suggest an autoimmune cause.
Every sign above is quoted from the sofidex article on Fibrous interstitial pneumonia. If you are not sure, err upward — it is always reasonable to be checked.