Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Use your local urgent mental health service, crisis line, or emergency department.
Call emergency services if there is immediate danger, such as severe breathing difficulty, loss of consciousness without quick recovery, a serious injury, or chest pain that could have a physical cause.
Move away from traffic, heights, water, or machinery before trying to manage a panic response.
Seek urgent help if anxiety is accompanied by thoughts of suicide, self-harm, or being unable to stay safe.
Arrange a routine appointment with a health professional if fear or avoidance is affecting work, education, relationships, health care, travel, or other important activities.
It is also reasonable to seek help if you spend substantial time planning around a trigger or have repeated panic attacks.
The article also says
Mention any physical symptoms that are new, unexplained, or not limited to feared situations.
They may need a separate medical assessment.
Every sign above is quoted from the sofidex article on Phobias. If you are not sure, err upward — it is always reasonable to be checked.