Positives

• A patient with severe Long COVID including auditory hallucinations and extreme histamine intolerance reported that 3,000–4,000mg niacinamide daily completely resolved their psychosis within 4 weeks and allowed them to reintroduce foods Reddit.
  
  
• A pharmacist with LC brain fog and headaches tried 250mg nicotinamide twice daily and within 24 hours their headaches resolved; after 11 days they felt fully functional Reddit.
  
  

Negatives

• A 5th-year long-hauler pushed back against the niacinamide success stories, reporting they had tried it along with every recommended supplement since 2021 with no results Reddit.
  
  

Hurdles & Side Effects

• A patient took 500mg niacinamide once and had a severe flush reaction with burning, redness, and itchy arms and legs requiring two antihistamines to control Reddit.