NAD+ and longevity: separating the science from the sales pitch

Start with measurement, not a protocol

People usually become interested in NAD+ because they feel more tired than they used to, or because they want to stay well for longer. Both are good goals. But fatigue in midlife has many common, treatable causes, including iron deficiency, thyroid disease, sleep apnea, low B12, poorly controlled blood sugar and mood problems.

A sensible first step is a baseline lab panel and an honest review of sleep, alcohol and activity. If NAD+ is still of interest after that, it can be tried as a time-limited experiment with a clear goal, rather than as an open-ended commitment.

What NAD+ actually does

Nicotinamide adenine dinucleotide, usually shortened to NAD+, is a coenzyme found in every cell. Its best-known job is shuttling electrons in the reactions that turn food into usable energy. The NIH Office of Dietary Supplements notes that NAD is needed by more than 400 enzymes.

NAD+ is also consumed by enzymes involved in DNA repair and in regulating which genes are switched on, including the sirtuin family. That second set of roles is what links NAD+ to aging research.

The decline-with-age claim

Animal studies and some human tissue measurements suggest NAD+ levels fall with age, and in mice, restoring NAD+ improves several markers of aging. That is a plausible mechanism, but it is a long way from showing that raising NAD+ in people makes them healthier or helps them live longer.

There is also no routine clinical test that tells you whether your own NAD+ is low, and blood levels may not reflect what is happening in muscle, brain or other tissues.

Why there are so many precursors

Your body builds NAD+ from several forms of vitamin B3. Niacin (nicotinic acid) and nicotinamide come from food and standard supplements. Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are newer supplement ingredients that feed into NAD+ through somewhat different pathways.

Each has trade-offs. Niacin at higher doses commonly causes flushing, and the adult upper limit for supplemental niacin is 35 mg per day unless a clinician is supervising its use. Nicotinamide does not cause flushing. NR and NMN are sold as dietary supplements, which do not go through FDA approval for safety and effectiveness before sale.

What human trials have found

The most consistent finding is that oral NR raises NAD+ and related compounds in blood. Beyond that, results are thin. A 2023 review in Science Advances concluded that oral NR has shown few clinically relevant effects in humans, found no evidence that it raises NAD+ in muscle, and noted that some studies overstate their findings. The most consistent possible signal was a reduction in some inflammatory markers.

A 2022 meta-analysis of NAD+ precursor trials found that niacin improved blood lipids but that precursor use was associated with higher fasting glucose. NR and nicotinamide showed no significant lipid effects, though the authors noted there were too few studies to be sure. The overall message: these compounds are biologically active, but the benefits for healthy adults remain unproven.

Injections versus oral forms

Injected NAD+ delivers the molecule directly rather than relying on precursors. Whether that leads to better outcomes is unknown, because there are very few controlled trials of NAD+ injections and no good head-to-head comparisons with oral precursors.

Injections can cause flushing, nausea, cramping, chest tightness or lightheadedness, particularly if given quickly, and injection-site reactions are possible. Anyone with significant heart, kidney or liver disease, or who is pregnant or breastfeeding, should not use NAD+ without specific medical advice.

How NAD+ is regulated

Injectable NAD+ in the U.S. is made by compounding pharmacies. Compounded drugs are not FDA-approved, and FDA does not review them for safety, effectiveness or quality before they reach patients. That does not make them illegal when prescribed and filled appropriately, but it does mean the evidence and quality checks behind them are different from an approved medicine.

Why people often feel better anyway

Many people report more energy after starting NAD+. Some of that may be real. Some may reflect the placebo effect, the attention of a new plan, or the natural tendency of symptoms to improve from a low point, which researchers call regression to the mean. That is why defining a specific goal in advance, and checking whether you reached it, matters so much.

B12, glutathione and other add-ons

B12 injections are well supported when someone is actually deficient, which is more common with age, certain medications such as metformin and some digestive conditions. For people with normal B12, extra B12 is unlikely to boost energy. Evidence for glutathione injections in healthy adults is weak. DHEA and pregnenolone are hormones, not vitamins, and should only be used with testing and supervision.

What has the strongest healthspan evidence

If your goal is to stay healthy for longer, the best-supported tools are not new molecules. They are consistent, well-studied habits whose effects on disease risk are measured in large populations.

• Regular aerobic activity: 150 to 300 minutes of moderate activity a week
• Strength training on at least two days a week
• Enough protein to protect muscle as you age
• Seven or more hours of sleep most nights
• Managing blood pressure, cholesterol and blood sugar
• Not smoking, and keeping alcohol low

If you decide to run a trial

A well-designed personal trial is short, specific and measurable. Pick one or two outcomes that matter to you, such as afternoon energy on workdays or how you feel the morning after training, and rate them for two weeks before you start so you have a baseline.

Agree on a time frame with your clinician, often 8 to 12 weeks, and change nothing else major during that window if you can. If you also start a new sleep routine or cut alcohol at the same time, you will not know which change helped. At the end, compare your ratings honestly and decide whether the cost and injections are worth continuing.

Report side effects as they happen rather than waiting for the review visit. Flushing or nausea during or after an injection is worth mentioning, and chest pain, fainting or a rash are reasons to stop and get medical advice.

Trying NAD+ at HealifyMD

If you and a licensed HealifyMD clinician decide a trial is reasonable, compounded NAD+ injections are listed from $199 per month, filled by a licensed U.S. pharmacy. This product is not FDA-approved. Labs are priced separately, and prices are confirmed during your eligibility review. Expect a defined review point to decide whether it is helping.