“Even patients in their twenties have symptoms of brain fog, fatigue, chronic inflammation, and chronic infection post-Covid,” Khan says. In her clinical experience, some report improvements in energy, mental clarity, migraines, and circadian disruption after using NAD-related therapies, especially during periods of high physical or cognitive stress.
“I have a lot of fitness enthusiasts [as patients], who recover better after an injury or an intense exercise routine,” Khan adds. “They feel like they can get more reps in, swim more laps, and their tissues aren’t as easily tired.”
Early research is also exploring NAD+’s role in neurodegenerative disease, inflammatory pain pathways, and addiction, though much of this work remains preliminary. In people with existing degenerative conditions—such as Parkinson’s disease, sarcopenia, or Alzheimer’s disease—NAD precursors may help slow decline. What remains unclear is whether starting supplementation can prevent disease or significantly alter the aging trajectory.
Safety, Side Effects, and Considerations
Among NAD+ boosters, NR supplements have the most robust safety data. They have been studied in doses ranging from 1,000 to 3,000 milligrams per day in healthy adults, with minimal to no side effects reported.
Although NMN has also been widely studied, it was sidelined for years by regulatory issues. In 2022, the US Food and Drug Administration stated that NMN couldn’t be sold as a supplement because it was being investigated as a drug. That decision was later reversed in 2025.
Niacin, another NAD+ precursor, is effective but less popular because high doses can cause flushing, where the cheeks become red and warm, and an increased heart rate due to vasodilation. While uncomfortable, this reaction isn’t generally dangerous.
Animal studies have raised concerns that extremely high doses of NAD+ precursors could promote tumor growth, which has led clinicians to exercise caution in patients with active cancer. In practice, NAD supplementation is typically avoided during active malignancy and considered on a case-by-case basis for those in long-term remission, often in consultation with an oncologist.
Importantly, no human clinical trials have shown increased risk from oral NAD precursors. Some researchers even hypothesize that NAD may support genomic stability and cancer surveillance. “If you don’t have signs of malignancy or a strong family history of genetic syndromes like BRCA and breast cancer,” Khan says, “I firmly believe that NAD+ is actually cancer-protective.” Still, long-term data are limited.
Pregnancy remains another gray area; most clinicians recommend avoiding NAD+ supplements during pregnancy due to a lack of safety data. Still, according to Khan, “there is some evidence that NAD+ can support fertility leading up to pregnancy, preserve egg quality, and sperm quality.”
NAD+ Precursors and IVs
Some products claim to deliver NAD+ directly, but physiologically, that’s unlikely to work when taken orally. NAD+ itself has a poor bioavailability and doesn’t cross the gastrointestinal tract or easily enter cells. That’s why most longevity experts recommend precursors, which can be absorbed, transported into cells, and converted into NAD+ internally.
IV and injectable NAD+ have surged in popularity, but evidence supporting their effectiveness is thin. No known transporter moves NAD+ directly from the bloodstream into cells, meaning much of the infused molecule may be rapidly broken down or excreted.
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