Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
If you have a diagnosed metabolic condition, follow your personal emergency plan during illness.
Call emergency services for a seizure lasting longer than expected, loss of consciousness, severe breathing difficulty, or if the person cannot be woken normally.
Show emergency staff any metabolic emergency letter or medical alert information.
Contact the metabolic team promptly if you are vomiting, cannot keep prescribed food or fluids down, are eating much less than usual, or have signs of infection.
Do not wait for severe symptoms if the plan says to seek help earlier.
Seek urgent medical assessment for repeated vomiting, worsening weakness, unusual behaviour, new confusion, marked drowsiness, or rapid breathing.
A baby who is difficult to wake, feeds poorly, repeatedly vomits, has breathing changes, or seems seriously unwell also needs urgent medical assessment, whether or not a metabolic condition is known.
Arrange routine follow-up for new but stable concerns such as increasing tiredness, reduced exercise tolerance, changes in movement, difficulty with the prescribed diet, or concerns about growth, learning, or treatment side effects.
Every sign above is quoted from the sofidex article on Inborn errors of metabolism. If you are not sure, err upward — it is always reasonable to be checked.