Positives

• A patient who megadosed thiamine mononitrate up to 500mg twice daily reported clear improvement in gastroparesis, POTS, polyneuropathy, restless legs, and irritable gut, describing their vagus nerve as “rejuvenated” Reddit.
  
  
• A person went from not being able to get up from sitting to walking almost 6 miles on some days within just 2 weeks of thiamine supplementation Reddit.
  
  
• A patient with neuro MS-like LC symptoms reported that B1 at 300–400mg daily with B2 and magnesium began to reverse whole-body stiffness, brain fog, and swallowing difficulty Reddit.
  
  

Negatives

• A patient who takes large dose thiamine daily reported no marked improvement in POTS symptoms, doubting it is a panacea for most long-haulers Reddit.
  
  
• A patient went up to 3,000mg thiamine HCl for weeks and it did not move the needle, except for one random day of sudden energy that could never be replicated Reddit.
  
  

Hurdles & Side Effects

• The original poster emphasized that thiamine supplementation can disrupt electrolytes, creating a “refeeding paradox” that requires careful cofactor management with magnesium and potassium Reddit.
  
  
• A patient experienced spinal pain whenever taking any form of thiamine, even with supporting vitamins, with higher doses causing chills and feeling unwell Reddit.