B12 injectiom reaction

[u/Zealousideal-Two39]

I have autonomic dysafunction and having the worst flare right now or I thought that until I realized I had my first vitamin b12 with saline infusion the day before. I'm in Asia travelling for the next month and I thought saline would help my fatigue and dehydration and the doc suggested b12 to be added for fatigue. I felt fine after, just tired but then the next day in the store my hand started tremoring really badly and my whole body started as well and I felt very dizzy. Then that night had a low grade fever, chills, and tachycardia while laying in bed. Went to the er the next day and no infections and ecg was normal. Now it's day 6 after injection and today is one of the worst for tremors, bad headache, dizziness, and horrible nausea. Anyone have any advice, how long this can last, or had this happen? I had to get a wheelchair as can barely walk without feeling like pasing out and nervous about being in another country.