Why the question of dosage is not trivial

NMN is not a substance where more automatically means better. Various clinical studies have investigated different dosages, and the results are not consistent. Some studies show strong effects at 250 mg, others only measure relevant functional improvements at 1,000 mg. The reason is that the two most important outcomes, first the NAD+ level in blood as a surrogate marker and second functional endpoints like muscle function or insulin sensitivity, do not necessarily run in parallel.

Additionally, most studies examine different populations: younger women with metabolic risk factors, older men with mobility limitations, healthy middle-aged adults. Which dose is best suited for which person cannot be determined with certainty from the current data. What can be said: a lower limit of 250 mg is established for measurable metabolic effects, and 900 mg appears to be the well-studied upper range for general health goals.

Study overview: Which doses were investigated?

The following table summarizes the most important controlled human studies with NMN dosage information, sorted by publication year:

Study	Dose / duration	Population	Key finding
Irie et al. 2020 Endocrine J	100 / 250 / 500 mg 4 weeks	10 healthy men 40–60 years	First human study. All doses safe and well tolerated. Dose-dependent NAD+ increase in blood, indications of improved muscle strength and walking speed.
Yoshino et al. 2021 Science	250 mg daily 10 weeks	25 premenopausal women Prediabetes / overweight	Significantly improved insulin sensitivity in skeletal muscle cells (euglycemic clamp). More favorable gene expression profile in muscle.
Yi et al. 2023 GeroScience	300 / 600 / 900 mg 60 days	80 adults 40–65 years	Dose-dependent NAD+ increase in all three NMN groups vs. placebo. 6-minute walk test improved. Biological age (Aging.AI) stable with NMN, increased with placebo.
Igarashi et al. 2022 NPJ Aging	250 / 500 / 1,000 mg 12 weeks	48 older men 65+ years	1,000 mg: Walking speed and grip strength significantly improved vs. placebo. No significant effect at 250 and 500 mg on these endpoints.
Huang et al. 2022 Front Aging	300 mg daily 60 days	66 healthy adults Average age 50 years	NAD+ increase in blood. Improvements in sleep, fatigue, and physical performance. Placebo-controlled.
Akasaka et al. 2023 Geriatr Gerontol Int	250 mg daily 24 weeks	14 male diabetics ≥65 years, limited mobility	No significant effect on grip strength or walking speed. Trend toward frailty improvement (p=0.066). Safe over 24 weeks. Shows: 250 mg is not enough for this vulnerable population.
Morifuji et al. 2024 Geroscience	250 mg daily 12 weeks	60 older adults Average age 65 years.	Primary endpoint (stepping test) not significant. 4-meter walking time improved (secondary endpoint). Sleep quality (PSQI) significantly improved. Funded by Meiji Holdings.

Table: Controlled human studies on NMN dosing (as of March 2026). Only placebo-controlled or open studies with dosing information. All studies indexed in PubMed.

What the dose-response data show

The methodologically strongest dosing study comes from Yi et al., published in GeroScience. The multicenter, double-blind, placebo-controlled study with 80 participants (40–65 years, 59% women) compared 300, 600, and 900 mg daily over 60 days. The result was clearly dose-dependent: All three doses significantly increased NAD+ levels in the blood compared to placebo, with 600 and 900 mg showing the strongest increase. ^[3]

Additionally, the 6-minute walk test improved in all NMN groups, and the biological age in the blood (Aging.AI score) remained stable, while it increased in the placebo group. This difference between groups reached statistical significance. This is a remarkable secondary finding but should be interpreted cautiously: The Aging.AI score is a biomarker-based estimate, not a clinically validated endpoint.

At the other end of the dosage spectrum is the study by Yoshino et al. in Science: Here, 250 mg daily over ten weeks was enough to measure significant improvements in insulin sensitivity in skeletal muscle cells in a small but methodologically very rigorous study. ^[2] This shows that low doses can be sufficient for specific metabolic endpoints in the right population.

The Igarashi study provides an important contrast: In older men over 65, 250 and 500 mg showed no significant effects on walking speed or grip strength, but 1,000 mg daily over 12 weeks did. ^[4] This suggests that older adults may need higher doses to achieve functional improvements, which is biologically plausible: With increasing age, not only does the NAD+ level decrease, but also the efficiency of NAD+ biosynthesis pathways.

Another example of this dose-population interaction is provided by Akasaka et al. 2023 in Geriatrics & Gerontology International: 14 older male diabetics with limited mobility received 250 mg daily over 24 weeks. No significant effect on grip strength or walking speed. The special feature of this study is its duration: 24 weeks is the longest published NMN RCT in humans so far. The result shows that 250 mg is not enough for an already weakened, older population. ^[7]

What a meta-analysis across all studies shows

Prokopidis et al. published in 2025 in the Journal of Cachexia, Sarcopenia and Muscle the first systematic meta-analysis on NMN and NR focusing on skeletal muscle mass and function. The result is sobering and important: summarized across all available RCTs, NMN shows no significant effect on muscle mass (SMI), handgrip strength, walking speed, or the 5-chair-stand test. ^[9]

This initially sounds contradictory to the individual studies described above. The reason lies in the heterogeneity of the studies: different populations, dosages, durations, and endpoints make direct comparison difficult. The meta-analysis shows that the positive findings from individual studies are not consistently reproducible across all available data. This is not proof of ineffectiveness but a clear signal that NMN is not a universally reliable effect for muscle function. For whom, at what dose, and over what period NMN works remains an open research question.

Sleep as a newly discovered endpoint

A previously little-noticed effect appears in two Japanese studies: Morifuji et al. 2024 in Geroscience studied 60 older adults with 250 mg daily over 12 weeks. The primary walking test was not significantly improved, but sleep quality measured by the Pittsburgh Sleep Quality Index improved significantly: less daytime sleepiness, better overall sleep score. ^[10] Additionally, Huang et al. had already observed improvements in self-reported fatigue and sleep in 2022.

Whether NMN directly affects sleep architecture or the circadian rhythm is not yet conclusively clarified mechanistically. NAD+ is involved in the regulation of SIRT1, which in turn is linked to the cell's circadian clock. This is biologically plausible but not proof. Sleep quality should currently be considered an interesting secondary finding, not a primary indication for NMN.

Time of intake: Morning or evening?

In all published controlled studies, NMN was taken in the morning, often with a meal or shortly after. A direct comparison between morning and evening intake in a controlled design is still missing.

The biochemical basis for a morning preference is plausible. The key enzyme of NAD+ biosynthesis, NAMPT (nicotinamide phosphoribosyltransferase), follows a circadian rhythm with a peak activity in the morning hours. Taking NMN at this time could theoretically synchronize with this natural activity curve. However, whether this is clinically relevant has not been proven.

Practically, taking it in the morning also supports routine formation: Together with other supplements or breakfast, NMN can easily be integrated into a fixed rhythm, which is crucial for long-term adherence.

NMN and TMG: Why many combine both substances

A frequently discussed topic in practice is the combination of NMN with TMG (trimethylglycine). The reasoning behind this: During the metabolism of NMN, nicotinamide is produced, which must be methylated in the body before it can be excreted. This step consumes S-adenosylmethionine (SAM), the universal methyl group donor. TMG can serve as a methyl group donor and help alleviate this potential bottleneck.

Direct clinical studies comparing NMN alone with NMN plus TMG are lacking. The combination is mechanistically justified and has a good safety profile but is not considered an established standard. People already taking methylation-relevant medications or supplements should consult a doctor.

Practical guidance: Who should take which dose?

Based on the study data, the following guideline values can be derived, which do not replace individual medical advice. For healthy adults under 50 with metabolic goals such as improved insulin sensitivity or general NAD+ optimization, the data from Yoshino et al. suggest that 250 to 300 mg daily can be effective. For adults over 50 or people with already measurable declines in physical performance, the data from Yi et al. and Igarashi et al. show that 600 to 1,000 mg daily have stronger and more reliable effects on NAD+ levels and muscle function. Starting with a dose of 300 mg and gradually adjusting based on tolerance is a pragmatic approach that corresponds to the study design of Yi et al.

In all studies, NMN was taken daily and continuously. Weekly breaks or cyclical intake have not been studied. Since NAD+ levels return to baseline after stopping, continuous intake is the more sensible approach if there is ongoing interest in the described effects.