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 new confusion, severe drowsiness, seizures, slurred speech, trouble swallowing, new weakness, inability to walk, or reduced consciousness.
This is especially important during the days after treatment for low sodium or another major electrolyte problem.
Emergency help is also needed for choking, difficulty breathing, blue or grey lips, or an inability to wake the person normally.
After hospital discharge, seek prompt medical advice if swallowing becomes harder, coughing repeatedly occurs during meals, movement declines, or there are signs of infection such as fever with breathing symptoms.
Routine appointments are appropriate for slow recovery, continuing stiffness or weakness, questions about rehabilitation, equipment needs, mood changes, and reviews of the condition that caused the original electrolyte problem.
Every sign above is quoted from the sofidex article on Osmotic demyelination syndrome. If you are not sure, err upward — it is always reasonable to be checked.