NMN and medications.

NMN is a precursor to NAD+, a coenzyme used throughout the body's energy chemistry, and blood levels of it fall with age. In Great Britain NMN is not yet authorised as a novel food, so it should not be on sale here as a supplement, although you may still see it sold; the duty to follow that rule sits with the seller, not with you, and the application to authorise it is still in progress, so this may change. Human trials since 2020 consistently show NMN raises blood NAD+. What that raised level does is a narrower question, and our records no longer grade it for any goal at all. Two claims often made for it are not supported by what we cite. It is not graded for energy, and the trial that measured this most directly, Pencina 2023, found no difference from placebo in muscle strength, fatigability, aerobic capacity or stair-climbing power. It is not graded for longevity either, because not one of the trials we cite measures lifespan, healthspan, frailty or biological age. A falling NAD+ level is a description of ageing, not evidence that topping it up changes how you age. Yoshino 2021 found 250mg/day improved muscle insulin sensitivity in prediabetic women, Igarashi 2022 reported gait speed and grip changes in older men that its own authors call nominal and in need of larger studies, and Pencina 2023 reported lower cholesterol, blood pressure and body weight at 1,000mg/day, though in that trial insulin sensitivity did not change and several of its authors work for the company that makes the product tested. A 2026 pooled analysis found a small fall in diastolic blood pressure, with the systolic effect reaching significance only in people over 60. The honest position is that it is not an established recommendation; the trials we cite used 250mg (Yoshino, Igarashi) and 1,000mg (Pencina), and none of them tested 500mg. The single most important point is a hard one: NMN is contraindicated with any cancer history. Preclinical studies show NAD+ precursors can support tumour cell survival and spread, and while human data are absent, the safe position is to exclude it entirely, so a cancer history must always be confirmed clear before use. On drug interactions, the one to raise is diabetes medication: NMN may modestly improve how the body responds to insulin, so alongside gliclazide or injected insulin your blood sugar could in theory go lower than your dose is set for. We hold no study of that combination, and the people in the NMN trials were taking no diabetes medication, so treat it as a precaution rather than a finding: monitor your levels and speak to your diabetes team before starting. It is otherwise well tolerated, with mild stomach upset the main complaint.