“Even patients in their twenties have symptoms of brain fog, fatigue, chronic inflammation, and chronic infection after Covid,” Khan said. In his clinical experience, some have reported 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,” added Khan. “They feel like they can get more reps, swim more laps, and their tissues don’t tire as easily.”

Early research also explored the role of NAD+ in neurodegenerative disease, inflammatory disease pathways, and addiction, although much of this work remains preliminary. In people with existing degenerative conditions-such as Parkinson’s disease, sarcopenia, or Alzheimer’s disease—Precursors of NAD may help slow down the decline. What remains unclear is whether initiation of supplementation will prevent disease or significantly alter the aging pathway.

Safety, Effects, and Considerations

Among NAD+ boosters, NR supplements have the strongest safety data. They are studied in doses from 1,000 on 3,000 milligrams per day in healthy adults, with little or no side effects reported.

Although NMN has been widely studied, it has been sidelined for many years by regulatory issues. In 2022the US Food and Drug Administration states that NMN cannot be sold as a supplement because it is 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 hot, and an increase in heart rate due to vasodilation. Although uncomfortable, this reaction is not usually dangerous.

Animal studies raised concerns that extremely high doses of NAD+ precursors could promote tumor growth, causing clinicians to exercise caution in patients with active cancer. In practice, NAD supplementation is usually avoided during active malignancy and is considered on a case-by-case basis for those in long-term remission, usually 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,” says Khan, “I believe that NAD+ is actually cancer protective.” However, 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. However, according to Khan, “there is some evidence that NAD+ can support fertility leading to pregnancy, preserve egg quality, and sperm quality.”

NAD+ Precursors and IVs

Some products claim to directly deliver NAD+, but physiologically, that doesn’t work when taken orally. NAD+ itself has poor bioavailability and does not cross the gastrointestinal tract or readily enter cells. That’s why most longevity experts recommend precursors, which can be absorbed, transported into cells, and converted to NAD+ internally.

IV and injectable NAD+ have increased in popularity, but the evidence supporting their effectiveness is thin. There is no known transporter that moves NAD + directly from the bloodstream into the cells, which means that most of the infused molecule can be rapidly broken down or excreted.