NMN and Insulin Sensitivity: What the Human Trials Actually Found

One small trial found that NMN improved muscle insulin sensitivity by about 25% in postmenopausal women with prediabetes. Most other human trials, and a 2025 meta-analysis of eight trials, found no meaningful effect of NMN on blood glucose, insulin or insulin resistance. That's one encouraging signal, not a proven benefit.

NMN (nicotinamide mononucleotide) is often marketed for metabolic health on the strength of that first trial, so it's worth looking at what each study actually measured. This guide goes through the human evidence trial by trial. For the basics of glucose, insulin and muscle first, start with our guide to what metabolic health really means for adults.

What is insulin sensitivity, and why does it matter?

Insulin sensitivity describes how well your body responds to insulin, the hormone that moves glucose out of the blood and into cells such as muscle. When sensitivity falls, the body needs more insulin to do the same job, and over time blood glucose can rise towards prediabetes and type 2 diabetes.

Muscle matters because it's one of the main places glucose goes after a meal. We explain the concept in more depth in a simple guide to insulin sensitivity.

A note on where we stand. NovusDNA is a UK supplement brand making clearly labelled, science-led supplements tested by a UKAS-accredited UK laboratory. Its NAD+ product, Longevity+, NovusDNA's NR-based formula, uses nicotinamide riboside chloride (NR) rather than NMN, so we've included the NR trials too. Neither ingredient has an authorised UK health claim for blood glucose or insulin, and nothing here should be read as one.

The trial that started it: Yoshino 2021

The most cited study is a 2021 trial published in Science by Yoshino and colleagues at Washington University. It was carefully designed but small.

Twenty-five postmenopausal women with prediabetes and overweight or obesity were randomised to 250 mg of NMN a day or placebo for 10 weeks. Insulin sensitivity was measured with a hyperinsulinaemic-euglycaemic clamp, the most detailed method available, which directly measures how much glucose the body takes up under a steady level of insulin. According to the US National Institutes of Health, muscle insulin sensitivity rose by about 25% in the NMN group.

The same summary is clear about what didn't change: blood glucose, blood pressure, blood lipids, body fat and liver insulin sensitivity. Lead researcher Samuel Klein told Washington University it was premature to make clinical recommendations from the results.

So the finding was specific: one tissue, one group of women, 10 weeks, and 13 people taking NMN.

What did the other human trials find?

When researchers measured glucose and insulin outcomes in other groups, NMN generally didn't move them.

The best overall picture comes from a 2025 meta-analysis in Current Diabetes Reports pooling eight randomised trials with 342 participants. It found no significant benefit of NMN on fasting glucose, fasting insulin, HbA1c or lipids, and only a borderline, non-significant change in HOMA-IR. The authors concluded their findings don't support NMN to improve glucose and lipid metabolism in the general population.

Why might the Yoshino result differ from the rest?

Three differences explain most of the gap.

1. Who was studied. Yoshino recruited women who already had prediabetes. Most later trials recruited healthy adults, where there's less room to improve.

2. How it was measured. Yoshino used the clamp, which isolates muscle glucose uptake. Most later trials used HOMA-IR, a simpler estimate from fasting glucose and insulin that doesn't isolate muscle.

3. What changed. The improvement was in muscle only. Blood glucose, the outcome most people care about, didn't change even in Yoshino's trial.

That makes muscle insulin sensitivity in people with prediabetes a reasonable research question, and nothing more yet. It's a narrower conclusion than you'll find on most NMN product pages.

What about NR (nicotinamide riboside)?

NR is another NAD+ precursor, and its insulin trials have also been disappointing. In a 2018 trial by Dollerup and colleagues, 40 sedentary, insulin-resistant men with obesity took 2,000 mg of NR a day for 12 weeks. Clamp-measured insulin sensitivity didn't change, although the dose was well tolerated.

A 2018 crossover trial by Martens and colleagues in 24 adults aged 55 to 79 found NR raised NAD+ in blood cells by about 60%, with no differences in glucose or insulin regulation.

So neither precursor has shown it improves blood glucose in humans, and we'd be wary of any brand, ours included, that suggests otherwise. For how the two compare more broadly, see how NMN and NR compare as NAD+ precursors.

What does the regulatory picture look like in the UK?

NR and NMN are in different positions in Great Britain. Nicotinamide riboside chloride is an authorised novel food that can be sold as a food supplement within set conditions of use. NMN was still under assessment in Great Britain as of October 2026 and isn't yet authorised. In the EU, the European Food Safety Authority gave one manufacturer's NMN a positive safety opinion in May 2026 at 300 mg a day, which is a step towards EU authorisation but not authorisation itself.

That's one practical reason NovusDNA built Longevity+ on NR chloride: it's the NAD+ precursor UK consumers can buy on a clear legal footing today. Neither ingredient has an authorised health claim for blood glucose or insulin, so a UK product saying NMN or NR "balances blood sugar" or "reverses insulin resistance" is making a claim it isn't allowed to make.

What actually improves insulin sensitivity?

Lifestyle changes have far stronger evidence than any NAD+ precursor. The NHS runs the Healthier You NHS Diabetes Prevention Programme, a nine-month programme of support with weight, healthy eating and physical activity for people at high risk of type 2 diabetes. NHS England says it cuts risk by more than a third for people who complete it.

Eligible adults aged 40 to 74 in England may be offered an NHS Health Check, but if you have symptoms or concerns about blood sugar, contact your GP rather than waiting. Muscle-building exercise matters too, because muscle is a major destination for glucose after meals.

FAQ

Does NMN lower blood sugar?

Human trials so far don't show that it does. Even in the 2021 Yoshino trial, which found improved muscle insulin sensitivity in women with prediabetes, blood glucose didn't change. A 2025 meta-analysis of eight randomised trials with 342 participants found no significant benefit on fasting glucose, fasting insulin or HbA1c. If you're concerned about blood sugar, speak to your GP rather than relying on a supplement.

How much NMN was used in the insulin sensitivity study?

The Yoshino 2021 trial used 250 mg of NMN a day for 10 weeks in 25 postmenopausal women with prediabetes, 13 of whom took NMN. Other trials have used 250 mg to 2,000 mg a day for 28 days to 12 weeks without meaningful changes in glucose or insulin markers. The original researchers said it was premature to make clinical recommendations, so 250 mg shouldn't be read as an effective dose for blood sugar.

Is NMN or NR better for insulin resistance?

Neither has shown a reliable benefit in humans. The one positive NMN trial found improved muscle insulin sensitivity in women with prediabetes, but other trials and a 2025 meta-analysis found no effect on glucose or insulin markers. A 2018 trial of 2,000 mg a day of NR in insulin-resistant men found no change either. The practical difference in the UK is legal status: NR chloride is authorised in Great Britain, while NMN was still under assessment in October 2026.

Can NAD+ supplements help with prediabetes?

There's no good evidence they do. Prediabetes is best addressed with weight management, diet and physical activity, which is what the NHS Diabetes Prevention Programme supports, and NHS England says it cuts risk by more than a third for completers. No NAD+ supplement has an authorised UK health claim for blood glucose. If you've been told your blood sugar is raised, ask your GP about the programme.

Is NMN safe to take?

The human trials here were small and lasted 28 days to 12 weeks, at 250 mg to 2,000 mg a day, so they say little about long-term use. In May 2026, the European Food Safety Authority considered 300 mg a day of one manufacturer's NMN safe for the general adult population, excluding pregnant and breastfeeding women. In Great Britain, NMN wasn't authorised as of October 2026. If you take medication for diabetes or any other condition, check with your GP or pharmacist before starting any NAD+ supplement.

NMN and insulin sensitivity is a story of one encouraging trial and a lot of follow-up that didn't confirm it. A 25% improvement in muscle insulin sensitivity in women with prediabetes is interesting science, but other trials and a 2025 meta-analysis found no benefit for blood glucose, and NR hasn't done better. NAD+ precursors aren't blood sugar treatments, and any brand worth trusting will tell you so.

For more on NR-based NAD+ precursor formulations, see Longevity+, without treating supplements as a way to manage blood glucose.

This article is for general information and isn't medical advice. If you're concerned about your blood sugar, speak to your GP. Food supplements should not replace a varied, balanced diet and healthy lifestyle.