The earliest blood NAD+ rise in the 25 published human NMN trials was reported after 8 days at 1,200mg, with rises after 14 days at 1,000 to 2,000mg and by day 30 at 300 to 900mg. Trials of physical and metabolic outcomes, such as walking, strength, sleep or insulin sensitivity, had a median length of 9.3 weeks, and 10 of those 14 ran 8 to 12 weeks. That makes RGENR8's 3-month plan a sensible length of time to try NMN: 90 capsules of Pure NMN Pro for £27.99 on your first order with code WELCOME20, which is 31p a day.
90 capsules, 500mg each, free UK delivery. See the 3-month plan
Timeline: the earliest check in each of the 25 human NMN trials
The earliest rises reported were in blood NAD+, between day 8 and day 30. The walking, exercise, sleep and insulin-sensitivity measures that changed did so between 6 and 12 weeks. This table lists every trial in our NMN Human Trials Dataset, ordered by the first timepoint in its record. We checked each trial against its PubMed record on 10 October 2026.
| Earliest timepoint | Outcome measured and reported | Trial length | Dose a day | People (n) | PubMed |
|---|---|---|---|---|---|
| 60 minutes | Blood NMN, nicotinamide and NAD+ after one dose, swallowed vs under the tongue: no difference between routes | One dose per period, 8-day washout | 250mg (one dose) | 14 | Wakabayashi 2026 |
| After one dose, post-exercise | Body-awareness questionnaires after exercise: no significant change with NMN | One dose, 60 minutes before exercise | 300mg (one dose) | 60 | Zhao 2026 |
| Followed 5 hours | Safety checks; NMN breakdown products in blood: rose with dose; no significant clinical symptoms | One dose, followed 5 hours | 100, 250 or 500mg (one dose) | 10 | Irie 2020 |
| Day 7 | Muscle biopsies after exercise: the post-exercise rise in muscle mitochondrial content seen on placebo did not occur with NMN | 7 days per condition | 1,200mg | 11 | Yang 2026 |
| Day 8 | Blood NAD: rose slowly and fell slowly after stopping; wide variation between people | 8 days, then 11-day washout | 1,200mg | 6 | Berven 2026 |
| Day 14 | Blood NAD+ and metabolites: dose-related rise | 14 days | 1,000 or 2,000mg | 32 | Pencina 2023 (14 days) |
| Day 14 | Blood NAD+ and metabolites: rose gradually (adults in hospital with COVID-19 and acute kidney injury) | 14 days | 2,000mg | 42 | Pencina 2025 |
| Day 14 | Whole-blood NAD+: NMN and nicotinamide riboside raised it to a comparable degree; nicotinamide did not | 14 days | 1,000mg | 67 | Christen 2026 |
| Not split (2-week course, followed to week 8) | Safety and platelet response in adults with immune thrombocytopenia: no dose-limiting toxicities reported | 2 weeks, followed to week 8 | 900mg | 25 | Li 2026 |
| Day 28 | Blood NAD+ higher; some body measures changed more than on placebo; strength and insulin sensitivity did not differ | 28 days | 2,000mg | 30 | Pencina 2023 (28 days) |
| Up to week 4 | Safety tests: no changes beyond normal variation; no severe adverse events | Up to 4 weeks | 1,250mg | 31 | Fukamizu 2022 |
| Day 30 | Blood NAD: higher in every NMN group at day 30 and day 60, highest at 600 and 900mg; six-minute walk distance rose more than on placebo | 60 days | 300, 600 or 900mg | 80 | Yi 2023 |
| Week 6 | Aerobic capacity: larger gains than placebo at the ventilatory thresholds at 600 and 1,200mg; VO2max unchanged | 6 weeks | 300, 600 or 1,200mg | 48 | Liao 2021 |
| Week 6 or 12 (not split in our record) | Whole-blood NAD+: higher; body composition unchanged; some 12-week data excluded after a supplier error | 12 weeks (6 or 12) | 250mg | 42 | Igarashi 2022 |
| Week 8 | Blood markers, hormones, skin scores: several markers changed from baseline; no placebo group | 8 weeks | 300mg | 17 | Morita 2022 (no PubMed record) |
| Within 8 weeks | Safety; NAD+ in blood cells: rose over the 8 weeks; no placebo group | 8 weeks | 250mg | 11 | Yamaguchi 2024 |
| Day 60 | Serum NAD+/NADH: rose more than on placebo, but the gap was not statistically significant | 60 days | 300mg | 66 | Huang 2022 |
| Week 10 | Muscle insulin sensitivity: rose with NMN, unchanged on placebo (postmenopausal women with prediabetes) | 10 weeks | 250mg | 25 | Yoshino 2021 |
| Week 12 | Sleep and fatigue questionnaires, physical tests: sit-to-stand and drowsiness changed, most in the afternoon NMN group | 12 weeks | 250mg | 108 | Kim 2022 |
| Week 12 | Safety; whole-blood NAD+: no abnormal results; NAD+ higher | 12 weeks | 250mg | 30 | Okabe 2022 |
| Week 12 | Serum NAD+ metabolites, arterial stiffness: serum nicotinamide higher; arterial stiffness not significantly different | 12 weeks | 250mg | 36 | Katayoshi 2023 |
| Week 12 | Plasma NMN and NAD+: both higher, with wide variation between people; no placebo group | 12 weeks | 250mg | 11 | Yamane 2023 |
| Week 12 | Stepping test: no difference on the main test; blood NAD+ higher at 12 weeks | 12 weeks | 250mg | 60 | Morifuji 2024 |
| Day 90 | Blood-cell markers, as reported in the paper; small, no placebo group | 90 days | 300mg | 8 | Niu 2021 |
| Week 24 | Safety; grip strength and walking speed in older men with diabetes: no improvement over placebo | 24 weeks | 250mg | 14 | Akasaka 2023 |
Where our record gives only the course length, that length is the earliest timepoint shown. Only Yi 2023 (day 30 and day 60) and Igarashi 2022 (week 6 or 12) are split further. "People (n)" counts everyone in the trial, placebo groups included. In total 884 people took part and 17 of the 25 trials had a placebo group. Several trials were funded by NMN makers or used NMN they supplied, and the papers say so. Most trials enrolled healthy adults. The exceptions are Pencina 2025 (adults in hospital with COVID-19), Li 2026 (adults with immune thrombocytopenia), Akasaka 2023 (older men with diabetes) and Yoshino 2021 (postmenopausal women with prediabetes). Full details, funding and downloads are in every published human NMN trial.
NAD+ levels: the fastest measured change
Blood NAD+ was higher in 11 of the 25 trials, and 4 of those 11 lasted 2 weeks or less. Berven 2026 gave 6 healthy adults 1,200mg a day and reported blood NAD rising slowly after 8 days, with wide differences between people. Pencina 2023, Pencina 2025 and Christen 2026 (141 people in total) reported higher blood NAD+ after 14 days at 1,000 to 2,000mg. Yi 2023, a randomised trial of 80 adults, reported higher blood NAD in all three NMN groups (300, 600 and 900mg) at day 30 and day 60. NMN is a building block your cells turn into NAD+, a molecule they use to make energy from food, so blood NAD+ is the usual first thing to measure.
Lower doses took longer in the record. At 250mg a day, Yamaguchi 2024 reported NAD+ in blood cells rising over 8 weeks, and Okabe 2022, Yamane 2023 and Morifuji 2024 reported higher blood NAD+ at 12 weeks. Igarashi 2022 reported higher whole-blood NAD+ in a course of 6 or 12 weeks. No 250mg trial in the dataset reports a rise before week 6. The trials measured NAD+ in whole blood, serum or blood cells, so treat the timings as approximate.
No repeated-dose trial gave exactly 500mg a day (see NMN 500mg studies). A 500mg capsule sits above the 250 to 300mg most trials used and below the 600 to 900mg groups in Yi 2023. The closest match is Yi 2023, where every dose from 300 to 900mg showed higher blood NAD by day 30.
Physical and metabolic outcomes: weeks to months
The 14 trials of physical and metabolic outcomes had a median length of 9.3 weeks, and 10 of them ran 8 to 12 weeks. Across all 22 trials with a set length the median was 8.3 weeks, and half of them (11) ran 8 to 12 weeks, 9 ran shorter and 2 longer. Results were mixed, so here they are by length. If you want to know how much to take, read our guide to NMN dosage per day.
The 14 are Yang 2026, Pencina 2023 (28 days), Liao 2021, Morita 2022, Yamaguchi 2024, Huang 2022, Yi 2023, Yoshino 2021, Igarashi 2022, Kim 2022, Katayoshi 2023, Yamane 2023, Morifuji 2024 and Akasaka 2023. Trials that measured only blood NAD+, safety, disease markers or blood-cell markers are left out, as are the 3 single-dose trials.
4 to 6 weeks
Pencina 2023 (28 days, 2,000mg, 30 people) reported some body measures changing more than on placebo, while muscle strength and insulin sensitivity did not differ. Liao 2021 (6 weeks, 48 recreational runners) reported larger gains than placebo at the ventilatory thresholds at 600 and 1,200mg, with VO2max unchanged.
8 to 10 weeks
Yi 2023 reported six-minute walk distance rising more than on placebo over its 60 days. Yoshino 2021 reported muscle insulin sensitivity rising at 10 weeks in 25 postmenopausal women with prediabetes, and unchanged on placebo. Morita 2022 and Yamaguchi 2024 ran 8 weeks with no placebo group.
12 weeks
Twelve weeks was the most common length, with six trials at 250mg a day. Kim 2022 (108 older adults) reported changes in sit-to-stand time and drowsiness, largest in the afternoon NMN group. Igarashi 2022 reported nominal gains in gait speed and left grip strength that the authors say need larger studies. Morifuji 2024 found no difference on its main stepping test, and Katayoshi 2023 found no significant difference in arterial stiffness.
Beyond 3 months
Akasaka 2023 ran 24 weeks in 14 older men with diabetes and reported no improvement over placebo in grip strength or walking speed. It is the longest trial in the dataset, and we have no published human trial data on longer use. If tiredness is what brought you here, see what the trials found on NMN for energy.
Three months of NMN, one capsule a day. See the 3-month plan
What trials measured before and after supplementation
Trials compare each person's starting values with their values after weeks of NMN, and 17 of the 25 also compared them with a placebo group. The placebo group is what lets researchers separate an NMN effect from chance and from the passing of time. Eight trials had no placebo group (Irie 2020, Niu 2021, Morita 2022, Yamane 2023, Yamaguchi 2024, Berven 2026, Li 2026 and Wakabayashi 2026), so their changes from baseline are weaker evidence. The measures were mostly blood values and physical tests, with a few questionnaires on sleep, fatigue and body awareness.
Why some people notice nothing
Some people will notice nothing from NMN, and the trials give several reasons to expect that. Most of the 25 trials measured blood chemistry, safety checks or physical tests, and few asked people how they felt. Kim 2022 did, with sleep and fatigue questionnaires in 108 older adults, and reported changes in drowsiness. Zhao 2026 gave one 300mg dose to 60 male students and reported no significant change in body-awareness questionnaires.
- People respond differently. Berven 2026 and Yamane 2023 both reported wide variation between individuals in blood NAD.
- Several trials found no difference on their main physical measure: Morifuji 2024 (stepping test), Akasaka 2023 (grip strength and walking speed over 24 weeks) and Katayoshi 2023 (arterial stiffness).
- Lower doses took longer. At 250mg, rises in blood NAD+ were reported at 6 to 12 weeks, so a few weeks is early to judge.
- The trials were small, with a median of 30 people, and several were funded by NMN makers or used NMN they supplied.
- NMN is a food supplement. RGENR8 does not promise any result.
The trials gave NMN every day, so a fair test means a steady daily dose. Three months of that is a reasonable point to judge NMN for yourself.
How a 3-month supply lines up with the trials
Of the 12 repeated-dose trials that used 300mg a day or less, 10 ran 8 to 12 weeks (56 to 84 days). One 500mg capsule a day for 90 days is 90 capsules, which covers that range with about a week to spare, and that is why our quarterly plan comes as one delivery of 90 capsules. Your first order is £27.99 with code WELCOME20 (the 3-month checkout applies it for you), which works out at 31p a day or £0.62 a gram, then £34.99 every 3 months. A single bottle of 30 capsules is £24.95 and covers about four weeks, shorter than most of the trials.
Pure NMN Pro is 500mg of beta-NMN per capsule, at least 99% purity, in a vegan HPMC shell with no fillers or binders. It is made to GMP-equivalent standards, every batch is tested by an independent accredited lab, and the Certificate of Analysis is available on request. Delivery in the UK is free, and unopened bottles have a 14-day money-back guarantee. For the price comparison, see the 3-month NMN supply prices in the UK, and for how the main brands compare, Best NMN supplement UK 2026: the main brands compared.
NMN is a food supplement, not a medicine. If you are pregnant, breastfeeding, on medication or managing a health condition, check with your GP first. In Great Britain NMN has no novel food authorisation yet, and an application to the Food Standards Agency, RP-2116, is at the risk assessment stage.
Common questions
How long does NMN take to work?
In the human trials that measured it, blood NAD+ was higher after 8 days at 1,200mg, 14 days at 1,000 to 2,000mg and 30 days at 300 to 900mg. Trials of physical and metabolic outcomes had a median length of 9.3 weeks. Whether you notice anything is personal, and RGENR8 does not promise it.
How long does NMN take to raise NAD+?
The earliest rise in our dataset was reported after 8 days at 1,200mg, with rises after 14 days at 1,000 to 2,000mg. At 250mg, trials reported higher NAD+ over 6 to 12 weeks. Berven 2026 found the rise was gradual and varied between individuals.
How long until I notice NMN working?
The trials mostly measured blood values and physical tests, so they cannot say when you will feel anything. Kim 2022 asked 108 older adults about sleep and fatigue over 12 weeks and reported changes in drowsiness and sit-to-stand time. Try three months at a steady daily dose, then judge for yourself.
What do NMN trials measure before and after supplementation?
Trials compare starting values with values after weeks of NMN: mostly blood NAD+, plus walking, strength, sleep and insulin tests. Seventeen of the 25 trials also had a placebo group, which is what lets researchers separate an NMN effect from chance. The other 8 had no placebo comparison.
Should I take NMN every day?
The trials gave NMN every day, so daily use is the pattern with evidence behind it. In Berven 2026, blood NAD rose slowly on NMN and declined slowly after stopping, which is a reason to take it daily.
What time of day should I take NMN?
The dataset does not settle this. Kim 2022 included an afternoon NMN group, and its largest effects were in that group, but no trial shows one time of day is better for NAD+. Pick a time you will remember and stick to it.
How long should I take NMN for?
The longest human trial in our dataset ran 24 weeks, so there is no long-term data to point to. A sensible plan is a three-month run at one daily dose, then judge for yourself. Check with your GP first if you are pregnant, breastfeeding, on medication or managing a health condition.
