NMN raises blood NAD+ in human trials, and NAD+ is part of how your cells make energy. A few trials also measured tiredness, sleep or physical performance, and the results were mixed and modest: Kim 2022 reported changes in drowsiness and a sit-to-stand test, while Akasaka 2023 found no gain in grip strength or walking speed over placebo.
The short answer
Of the 25 published human trials in our NMN Human Trials Dataset, 10 measured something energy-related, such as fatigue, drowsiness, sleep, walking, strength or aerobic capacity. Five reported an improvement on at least one of those measures, two reported none, and three did not report a separate result in the summaries we hold. The other 15 looked at blood NAD+, safety or other markers.
So NMN has a plausible link to energy and some early, small signals, but no trial shows it reliably lifts tiredness. Most trials were small, several ran under 12 weeks, and some were funded by NMN makers, as the papers state. If you are curious, that is a fair reason to try it as part of a sensible routine. It is not a reason to expect a change by a set date.
How NAD+ ties to cellular energy
Your cells turn food into usable energy inside mitochondria, and NAD+ is one of the molecules that carries electrons through that process. NMN is a building block your body converts into NAD+. A review in Nature Reviews Molecular Cell Biology by Covarrubias and colleagues describes NAD+ as central to energy metabolism and notes that NAD+ levels fall in several tissues with age (doi 10.1038/s41580-020-00313-x).
That is the reason people ask about NMN and energy. The gap is in the middle. A higher NAD+ reading in blood does not by itself tell you whether someone will feel less tired, which is why the trials that measured feelings and performance directly matter more than the ones that only measured blood.
Every human NMN trial that measured an energy-related outcome
Here are the 10 trials in the dataset that measured fatigue, drowsiness, sleep, walking, strength, aerobic capacity or a general wellbeing questionnaire. We checked each against its PubMed record on 10 October 2026. Doses are per day unless marked as single doses, and "people" counts everyone in the trial, placebo groups included. The last column is what the authors reported, in short.
| Trial | Dose per day | Length | People | What was measured | What the authors reported |
|---|---|---|---|---|---|
| Irie 2020 | 100, 250 or 500mg (single doses) | One dose, followed 5 hours | 10 | Safety checks, including sleep quality | No significant clinical symptoms or vital-sign changes reported; no separate sleep result in the summary we hold |
| Liao 2021 | 300, 600 or 1,200mg | 6 weeks | 48 | Aerobic capacity on exercise testing | Larger gains at the ventilatory thresholds at 600 and 1,200mg than on placebo; VO2max, O2-pulse and peak power unchanged |
| Huang 2022 | 300mg | 60 days | 66 | Six-minute walk test, SF-36 questionnaire, blood NAD+/NADH | Changes in SF-36 reported; the NAD+/NADH gap over placebo was not statistically significant; no separate walk-test result in the summary we hold |
| Igarashi 2022 | 250mg | 6 or 12 weeks | 42 | Gait speed, grip strength, body composition | Nominally significant changes in gait speed and left grip strength that need larger studies; no effect on body composition |
| Kim 2022 | 250mg | 12 weeks | 108 | Sleep quality and fatigue questionnaires; sit-to-stand and other physical tests | Significant interactions for five-times sit-to-stand and drowsiness, largest in the afternoon NMN group |
| Akasaka 2023 | 250mg | 24 weeks | 14 | Grip strength and walking speed | No improvement over placebo; no severe adverse events |
| Pencina 2023 | 2,000mg | 28 days | 30 | Muscle strength, aerobic capacity, physical performance | Strength and aerobic capacity did not differ from placebo; blood NAD+ was higher |
| Yi 2023 | 300, 600 or 900mg | 60 days | 80 | Six-minute walk distance, blood NAD | Walk distance rose more than on placebo; blood NAD higher in all NMN groups |
| Morifuji 2024 | 250mg | 12 weeks | 60 | Stepping test (main); 4-metre walk and sleep questionnaires (secondary) | No difference on the main test; shorter walking time and two sleep questionnaire scores better than placebo at 12 weeks |
| Yamaguchi 2024 | 250mg | 8 weeks | 11 | Safety, including sleep measures; NAD+ in blood cells | Well tolerated; blood-cell NAD+ rose; no separate sleep result in the summary we hold; no placebo group |
What the table adds up to
- 10 of the 25 trials measured an energy-related outcome.
- 5 reported an improvement on at least one: Liao 2021, Igarashi 2022 (nominal, needing larger studies), Kim 2022, Yi 2023 and Morifuji 2024 (secondary measures only).
- 2 reported no improvement: Akasaka 2023 and Pencina 2023, for strength, walking and aerobic capacity.
- 3 did not report a separate result for the outcome in the summaries we hold: Irie 2020, Huang 2022 and Yamaguchi 2024.
- Only Kim 2022 used fatigue questionnaires. Its reported effects were on drowsiness and sit-to-stand, and the summary we hold does not report a fatigue result.
The trials are small, so one trial does not settle anything. Full details, funding and downloads are in every published human NMN trial. For the main brands compared, see Best NMN supplement UK 2026: the main brands compared.
What this means if you are tired
NMN is a food supplement, not a substitute for sleep, food or movement, and none of the trials tested it as one. If you are tired most days, the first step is boring and worth doing: look at sleep, stress, alcohol, diet and activity.
Persistent tiredness can also have causes that a supplement will not touch. The NHS lists several, and a GP can check things like iron levels and thyroid function with a blood test. Read the NHS page on Tiredness and fatigue, and book an appointment if it has lasted weeks or comes with other symptoms. Check with your GP before starting NMN if you are pregnant, breastfeeding, on medication or managing a health condition.
How people take it
The energy-related trials gave NMN daily, mostly at 250mg to 300mg, with the higher-dose groups going up to 1,200mg and 2,000mg. Our guide to how much NMN per day sets out the doses used across all 25 trials. The trials that looked at sleep, drowsiness or walking ran 6 to 24 weeks, most often 12, so read how long NMN takes to work before deciding whether it is doing anything for you.
Pure NMN Pro is one 500mg capsule a day. The label says it supports healthy cell function and may support overall vitality and well-being, and that is as far as we go. Each capsule has 500mg of beta-NMN, at least 99% purity, in a vegan HPMC shell with nothing else added, and every batch is independently tested.
What it costs
One capsule a day is 30 capsules a month. A single bottle of 30 is £24.95. On the 3-month plan, your first order is £27.99 with code WELCOME20, which is 31p a day, then £34.99 every 3 months. Twelve weeks is also the length most of the trials above ran. See Pure NMN Pro for the current plans.
In Great Britain NMN has no novel food authorisation yet. An application to the Food Standards Agency, RP-2116, is at the risk assessment stage.
Common questions
Does NMN help with energy?
NMN raises blood NAD+ in human trials, and NAD+ is part of how cells make energy. Only a few trials measured tiredness or physical performance, and the results were mixed and modest. Kim 2022 reported changes in drowsiness and a sit-to-stand test, while Akasaka 2023 reported no gain in grip strength or walking speed over placebo.
How long does NMN take to help with tiredness?
The trials that looked at sleep, drowsiness or walking ran 6 to 24 weeks, most often 12. Blood NAD+ rose sooner than that, so give a steady daily dose two to three months before judging. How you feel is personal and not promised.
Can NMN replace sleep?
No. NMN is a food supplement, and none of the trials tested it as a substitute for sleep, food or exercise. If you are tired all the time, speak to your GP, who can check things like iron and thyroid function.
What dose of NMN did the energy-related trials use?
They used 250mg to 2,000mg a day. Kim 2022, Morifuji 2024 and Akasaka 2023 used 250mg, Huang 2022 used 300mg, Yi 2023 used 300 to 900mg and Liao 2021 used 300 to 1,200mg. One Pure NMN Pro capsule is 500mg.
Is NMN legal to buy in the UK?
In Great Britain NMN has no novel food authorisation yet. An application to the Food Standards Agency, RP-2116, is at the risk assessment stage. Check with your GP before taking it if you are pregnant, breastfeeding, on medication or managing a health condition.
