Why I Stopped Taking NMN: Side Effects & What Happened

Top quit reason: Nausea · Expert who quit: Dr. Brad Stanfield · Common complaint: Insomnia · Storage issue: Degrades with heat · Effect after stop: Benefits fade gradually

Why should you not take NMN?

NMN research looked promising in mice and preclinical studies. Human clinical trials have not delivered the same results. A key trial involving 60 long COVID patients given NR (a related NAD+ precursor) showed NAD+ levels increasing 2.6 to 3.1 times over 20 weeks—yet no measurable improvements in cognition, fatigue, sleep, or anxiety were observed (Dr. Brad Stanfield Blog). That’s a stark gap between biomarker elevation and actual benefit.

Product quality and stability

Beyond the science, practical issues shape whether people stick with NMN. The supplement degrades when exposed to heat or moisture, meaning improper storage can render a bottle useless before it’s even finished. Quality control in the supplement industry is notoriously uneven, and there’s no standardized dose-response curve from any study to guide consumers (DrDrayzday YouTube Video).

Side effects like nausea and insomnia

Nausea tops the list of reasons clinics hear from users who quit, particularly among those just starting. Insomnia is the nighttime counterpart—dose-related and disruptive enough that many users abandon the supplement within weeks. These aren’t rare anomalies; they’re frequent enough to show up consistently across user reports and clinical reviews (PerfectB.com NAD Clinic Review).

“I took it for 6 months and I took it every day… at the end of the 6 months, I was actually disappointed cuz I had hoped that it would be helpful. It wasn’t. I saw no difference.”

— Dr. Joanette, Medical Professional (Dr. Joanette YouTube Video)

The pattern: promising preclinical science, underwhelming human outcomes, and a growing body of personal accounts from both everyday users and credentialed professionals describing the same experience. The gap between what NMN was supposed to do and what it actually does for most people is the core reason many quit.

Is there a downside to NMN?

Yes, and it shows up in more ways than an upset stomach. The downsides fall into three buckets: immediate side effects, long-term unknowns, and opportunity costs.

Anxiety and other side effects

Beyond nausea and insomnia, some users report heightened anxiety, particularly at higher doses. The dose-response relationship for NMN has not been established in any clinical guideline, leaving users essentially guessing. For those already managing stress or sleep issues, adding a supplement with unpredictable effects can make things worse rather than better.

Lack of long-term data

Short-term NMN studies show no obvious adverse effects, but that’s a very low bar. Long-term safety data simply doesn’t exist in any rigorous quantity. The Nature Metabolism journal has published work flagging the need for caution in aging-related NAD+ modulation specifically because of theoretical cancer risks (PerfectB.com NAD Clinic Review). The concern: if NAD+ boosters fuel cancer cell metabolism the same way they theoretically support healthy cells, long-term users could be unwittingly raising their risk.

No direct human study has confirmed cancer causation from NMN, but the absence of data is not the same as evidence of safety. Researchers point to the beta-carotene example: promising in preclinical work, then shown to increase cancer risk in human trials. It’s an uncomfortable parallel that the supplement industry prefers to sidestep.

When benefits fade on stopping

Users who stop taking NMN often notice their energy slipping back to where it was before they started. This isn’t withdrawal or a crash—it’s a return to baseline. The body’s own NAD+ production was never permanently altered by supplementation; it was simply receiving external support that has now been removed. The decline feels significant precisely because the benefit was real, if modest (PerfectB.com NAD Clinic Review).

Dr. Brad Stanfield put it plainly in a public statement: there are interesting mouse and single-cell studies on NAD+ precursors, but the human data demonstrating a benefit is lacking. He switched to a small dose of niacin, regular exercise, good diet, safe fasting periods, and restful sleep. His explicit reason: we don’t know the long-term effects of boosting NAD+ to very high levels (NMN.com Article).

The downside of NMN isn’t just the side effects or the cost. The supplement occupies a space in your routine that may be better filled by lifestyle interventions with more established track records.

What do doctors say about NMN?

Medical professionals and science communicators have started speaking up, and their assessments are notably more skeptical than the supplement marketing.

Dr. Brad Stanfield quits NMN

Dr. Brad Stanfield is a physician and popular science YouTuber whose decision to stop taking NMN and NR is among the most cited in this space. His reasoning is grounded in evidence hierarchy: the human data simply doesn’t support the claims made for these supplements. His switch to 50 mg niacin daily was deliberate, though he acknowledges that niacin has limited human evidence for anti-aging—mainly one study on muscle performance in mitochondrial disease at a dose of 1000 mg (NMN.com Article).

“There’s interesting mice and single cell studies regarding NAD+ precursors, however the human data demonstrating a benefit is lacking. I focus on stopping my NAD from declining by using a small dose of Niacin, regular exercise, a great diet, periods of safe fasting, and restful sleep. Furthermore we don’t know the long-term effects of boosting NAD+ to very high levels.”

— Dr. Brad Stanfield, MD/YouTuber

His age—early thirties—matters in context. At that stage of life, with a healthy lifestyle, NAD+ levels are likely sufficient without supplementation. The calculus changes for older adults, a point his critics have made explicitly.

Clinical reviews from NAD clinics

Clinics specializing in NAD+ therapy report that nausea and insomnia are the most common complaints leading to discontinuation. Plateauing effects after months of use are another consistent theme—users report reaching a point where continued supplementation produces no further perceptible benefit, making the ongoing cost harder to justify.

DrDrayzday, a dermatologist and YouTuber, has discussed the NMN landscape extensively. His assessment: the research looks solid in mice, but human clinical trials have not delivered. He notes that short-term studies show no adverse effects, but “there’s definitely not sufficient data here to say for sure what the long-term safety is” (DrDrayzday YouTube Video).

Low dose niacin versus NMN

Stanfield’s preference for niacin over NMN or NR is based on familiarity and cost rather than superior evidence. More human studies support anti-aging effects of NMN than niacin, which somewhat undermines his choice—but niacin is dramatically cheaper, and the evidence gap may close as more research emerges. Dr. Joanette’s personal 6-month experience with a reputable NMN brand produced no benefits, adding a personal-data point to the clinical evidence (Dr. Joanette YouTube Video).

The implication for anyone considering NAD+ boosters: the choice between NMN, NR, and niacin is not settled science. Each has limitations, and the decision should factor in your age, health status, budget, and tolerance for uncertainty.

Is NMN toxic to the liver?

The short answer: not confirmed, but the question deserves more attention than the supplement industry typically gives it.

Liver safety data

No clinical data has demonstrated liver toxicity from NMN supplementation in humans. Short-term studies have not shown obvious adverse liver effects, but these trials are typically too short and too small to detect rare or long-latency harms. The theoretical mechanism for concern exists: nicotinamide, a metabolite of NMN, is processed through the liver, and sustained high levels could theoretically stress hepatic function over time.

There’s also the unknown of drug interactions. NMN’s metabolic pathway involves nicotinamide, which may interact with certain medications, including some used for epilepsy and seizures, though this remains unstudied at clinical scale (DrDrayzday YouTube Video).

NMN, cancer risk, and the NAD+ connection

This is where the science gets genuinely uncomfortable. The theoretical concern: cancer cells rely heavily on NAD+ for their rapid metabolism. If boosting NAD+ systemically also fuels tumor growth, long-term NMN users could be unknowingly raising their cancer risk. The Nature Metabolism journal has published work debating exactly this question, and the scientific community is not close to a resolution (PerfectB.com NAD Clinic Review).

The beta-carotene precedent haunts this debate. Beta-carotene looked promising in preclinical studies for antioxidant effects. Large-scale human trials showed it increased cancer risk in smokers. The lesson: results in mice and cells do not reliably predict human outcomes, and the history of supplements contains more than a few expensive surprises.

For potential users with a family history of cancer, existing liver conditions, or medications with unknown NMN interactions, the risk calculus shifts considerably. The absence of confirmed harm is not the same as evidence of safety, and the regulatory signal suggests more is going on than the supplement marketing admits.

What happens when you stop taking NMN?

The experience varies, but the overall picture is more benign than the supplement marketing might imply.

Energy and focus fade gradually

Most users who quit NMN report a gradual decline in energy over days to weeks rather than an acute crash. This is consistent with the understanding that NMN was supplementing existing NAD+ physiology rather than correcting a deficiency—the body simply returns to its baseline production level.

This is sometimes mislabeled as “withdrawal,” but there’s no known mechanism by which NAD+ boosters suppress the body’s own NAD+ production. You’re not unlearning how to make your own NAD+; you were never dependent in that sense (PerfectB.com NAD Clinic Review).

Before and after experiences

Reddit-style accounts and personal testimonials consistently describe a similar arc: initial optimism during the first weeks or months, a plateau where effects stabilize or diminish, and then a gradual unwinding of perceived benefits after stopping. The before-and-after framing is common, but it’s worth noting that perceived energy levels are subjective and influenced by expectation, lifestyle changes, and baseline variation.

Dr. Lance Hitchings, 71, has pushed back on Stanfield’s cessation advice from the perspective of an older biohacker. His argument is essentially that age changes the math: a 71-year-old with declining NAD+ may have a stronger case for supplementation than someone in their early thirties with a healthy lifestyle. Age is likely a significant moderator of both benefits and risks (Lance Hitchings YouTube Response).

Stopping NMN means accepting a return to baseline, but it also means removing exposure to a compound with unresolved long-term safety questions. Older adults with clinically low NAD+ may still favor continuation under medical supervision, while younger users with good lifestyle habits face a stronger case for stopping.

Comparing the alternatives

Three main NAD+ precursor options dominate the market: NMN, NR (nicotinamide riboside), and niacin. Each has a different evidence profile, cost structure, and risk level.

NMN and NR are chemically related and similarly priced—typically around $60 per bottle. NR breaks down via gut bacteria to nicotinic acid, effectively becoming a form of vitamin B3 in the body (Dr. Brad Stanfield Blog). Niacin is available in 500 mg tablets for a few cents per dose. If you pay $60 for NR and your body converts it to niacin, you’re paying a premium for the delivery mechanism rather than the molecule itself.

None of the three is clearly superior for general anti-aging use. NR has the most directly negative human trial data. Niacin has the longest track record and lowest cost but weaker anti-aging evidence. NMN sits in the middle: the most studied in terms of preclinical promise, but the clearest gap between mouse and human results.

Related reading: Why people stop taking NMN: A clinical review of NAD supplement side effects

My NMN struggles mirror debates in creatine side effects analysis, where science uncovers risks prompting users to reconsider daily intake.

Frequently asked questions

The bottom line

The NMN story is a case study in the gap between supplement hype and clinical reality. Preclinical data looked strong, user testimonials were enthusiastic, and the science of NAD+ decline with age made intuitive sense. What the evidence actually shows in humans is different: a 20-week trial in 60 patients where NAD+ tripled, yet no symptoms improved.

Dr. Brad Stanfield stopped taking NMN and NR for a defensible reason: the human data does not support the claims made for these supplements. His alternative—lifestyle—is less glamorous but better supported by evidence. For anyone currently taking NMN or considering it, the practical case is weak: no confirmed dose-response, regulatory concerns in the U.S., and a growing body of personal accounts from physicians describing no benefits after months of consistent use.

For anyone already taking NMN, the decision to continue should factor in age, health status, budget, and tolerance for uncertainty. For those not yet taking it, the evidence bar has not been met. Lifestyle interventions—exercise, diet, fasting, quality sleep—maintain NAD+ without the cost and uncertainty. Users who ignore the clinical data and start anyway risk wasting $60 per bottle on a supplement that converts to a penny’s worth of vitamin B3 in their bodies.