Positives

• One person found that taking NAC significantly improved their breathing problems within two months, noting it as the most effective supplement among many tried Reddit.
  
  
• One person reported that NAC helped alleviate their fatigue, particularly during a challenging period, by reducing their dosage to avoid side effects Health Rising.
  
  
• One person described NAC as providing the “most benefit” among supplements tried, specifically improving their fatigue without causing stomach issues Health Rising.
  
  
• One patient with post-COVID brain fog experienced “clearer thinking” and improved memory after taking NAC, which greatly enhanced their cognitive function Mayo Clinic Connect.
  
  

Negatives

• One person reported that starting NAC at 600 mg twice a day caused persistent stomach upset, described as “hunger pangs but worse” Health Rising.
  
  
• One person experienced stomach discomfort after taking NAC, despite their doctor’s recommendation, leading them to discontinue use Health Rising.
  
  

Hurdles & Side Effects

• In 2020 the FDA sent warning letters arguing NAC was excluded from the supplement category because it had been approved as the prescription drug Mucomyst back in 1963, which prompted Amazon to pull all NAC products in May 2021 — the agency eventually issued enforcement-discretion guidance in 2022 letting NAC supplements stay on shelves, but a generation of buyers had to scramble for alternative vendors Nutraceuticals World.
• Phoenix Rising members report that 1,800-2,400 mg/day is a common dose but going above 2,400 mg often causes loose bowels, bloating, and a 6-7 lb weight gain, and that the bottle’s rotten-egg sulfur smell can be so strong that patients dilute it in caffeine-free diet soda just to keep it down Phoenix Rising.