NAD+ supplementation in the form of nicotinamide riboside (NR, Niagen) shows early promise in the treatment of fatigue and brain fog in long COVID.[1] A clinical trial tested the effects of NR on hospitalized patients with persistent symptoms after COVID-19, with an average age of 45 years.[1] Participants received 2000 mg of NR daily for 20 weeks or placebo for 10 weeks followed by NR for 10 weeks.[1] NR supplementation significantly increased NAD+ levels up to 3.1-fold after 5 to 10 weeks.[1] There were significant within-group improvements in fatigue severity, sleep quality, and depressive symptoms after 10 weeks of NR use.[1] Although statistically significant differences were not observed between the NR and placebo groups, many participants showed encouraging improvements after at least 10 weeks.[1] The study mainly focused on changes in cognitive performance, fatigue, mood and sleep quality using validated scales.[1] Findings suggest that increasing NAD+ may provide relief from long-term COVID symptoms in some individuals.[1]