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 symptoms that would normally require emergency care, such as severe breathing difficulty, signs of a stroke, loss of consciousness, or severe chest pain.
Follow local emergency guidance.
Contact emergency services or a local crisis service, and stay with a trusted person if possible.
Seek prompt medical assessment for a new, persistent, or worsening physical symptom.
Do not assume that a symptom is caused by anxiety simply because you have experienced health anxiety before.
Get urgent mental health help if you have thoughts of suicide, intend to harm yourself, cannot keep yourself safe, or feel at immediate risk.
Arrange a routine appointment if health fears persist, repeatedly return after reassurance, or interfere with sleep, relationships, work, study, or normal activities.
You do not need to wait six months before asking for support.
Routine follow-up is also appropriate if you are avoiding medical care, repeatedly requesting tests, or spending large amounts of time checking your body or searching for symptoms.
Bring a summary of your concerns and previous investigations if possible.
Every sign above is quoted from the sofidex article on Illness anxiety disorder. If you are not sure, err upward — it is always reasonable to be checked.