Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
These concerns often need prompt assessment but are not always emergencies.
Call emergency services for severe trouble breathing, chest pain, fainting, uncontrolled bleeding, signs of stroke, or sudden severe abdominal pain—especially pain under the left ribs with dizziness or weakness.
These symptoms require immediate evaluation regardless of whether they are caused by myelofibrosis.
Seek urgent medical guidance for a fever if the care team has said that white blood cell levels or treatment place you at high infection risk.
Follow the specific fever plan provided by the treating clinic.
Routine follow-up usually includes a discussion of symptoms, a physical examination, and complete blood counts.
The clinician may check spleen size and review weight, activity level, bleeding, infections, and treatment side effects.
Molecular or marrow testing may be repeated if the disease appears to change, but it is not necessarily needed at every visit.
The article also says
Tell the care team between scheduled visits about increasing fatigue, new bruising, persistent fever, worsening abdominal fullness, unexplained weight loss, or a clear change in night sweats.
Every sign above is quoted from the sofidex article on Agnogenic myeloid metaplasia. If you are not sure, err upward — it is always reasonable to be checked.