For years, NAD has been sold as a "youth molecule" that fades with age and needs topping up. A study of 1,068 adults published in Nature Metabolism on 4 November 2026 points in another direction: in healthy people, NAD levels in the blood did not fall with age. They were lower, however, in people with cardiovascular disease and high blood pressure. Here is what the finding means for your heart, for NAD supplements and for the blood tests you already have.
What the Vilnius study found
Researchers at Vilnius University in Lithuania, working with two Lithuanian laboratory companies, measured NAD (nicotinamide adenine dinucleotide) in whole blood 1,340 times in 1,068 adults. Samples came from a finger-prick dried blood spot collected under standardised conditions. The group included healthy volunteers and people living with long-term conditions.
- In healthy adults, whole-blood NAD did not decline with age. It stayed stable in men and rose slightly in women.
- NAD was lower in people with long-term conditions, specifically cardiovascular disease and hypertension. The clearest gap was in people with high blood pressure.
- The authors state that the study was not designed to test cause and effect, and that it gives no direct evidence that NAD supplements could treat heart disease or hypertension.
The lead researcher, Dr Dalius Ratautas, summed up the shift in a university press release: the prevailing narrative has been that NAD declines as we age and must be restored, and the team now asks whether NAD levels could say something about cardiovascular health instead.
A second cohort points the same way
The Lithuanian result does not stand alone. In May 2026, a team from Amsterdam UMC published a separate Nature Metabolism paper that measured whole-blood NAD with a validated mass spectrometry method across seven independent human cohorts. NAD stayed remarkably stable with age and did not change with lifestyle interventions, but it rose as expected when people took nicotinamide riboside (NR), an NAD precursor. The authors concluded that blood NAD is a poor biomarker of ageing.
| Question | Vilnius study (Nov 2026) | Amsterdam UMC study (May 2026) |
|---|---|---|
| Does blood NAD fall with age in healthy adults? | No: stable in men, slightly higher in women | No: stable across seven cohorts |
| Does it change with disease or lifestyle? | Lower in cardiovascular disease and hypertension | No change with lifestyle interventions |
| Does it respond to NAD precursors? | Not tested | Yes, it rises with nicotinamide riboside |
| Sample type | Finger-prick dried blood spot | Whole blood, mass spectrometry |
Why blood NAD is not the whole story
Most of the NAD in whole blood sits inside red blood cells, which have a metabolism of their own. Blood levels may therefore not mirror NAD in muscle, heart or brain tissue, a limitation that commentators in the same journal also raised. The Vilnius team also notes that the people with long-term conditions were taking medication, so the lower values could reflect treatment as much as the disease itself. In short, low blood NAD is a signal worth studying, not a diagnosis.
What this means for NAD supplements
NAD boosters such as NR, NMN (nicotinamide mononucleotide) and intravenous NAD drips are heavily marketed as anti-ageing products. The new data weaken the main sales argument: if blood NAD does not drop in healthy ageing, there is no general "deficit" to correct. Recent trials and reviews add to that picture:
- In older adults with high blood pressure, adding NR to a walking programme did not lower daytime systolic pressure more than exercise alone.
- In older adults with mild memory problems, NR doubled blood NAD over 12 weeks but did not improve memory, total brain blood flow or blood pressure.
- Pooled trials of oral NMN found good short-term tolerability and, at most, a small drop in diastolic pressure, with no clear effect on glucose, HbA1c or cholesterol.
- A 2026 review of IV NAD therapy found the human evidence sparse and mostly uncontrolled, with side effects such as nausea, flushing and chest discomfort, and no long-term safety data.
Bear in mind that food supplements are not licensed like medicines: in the US the FDA does not approve them for safety or effectiveness before they are sold, and in the UK manufacturers are likewise responsible for their own products. If you take or plan to take an NAD product, tell your GP, especially if you have heart disease or take blood pressure medication.
Which tests can monitor or screen for this?
A blood NAD test is not part of routine care, and no reference range exists for clinical decisions. The tests that matter for the heart and blood pressure risk the study points to are already standard:
- Blood pressure readings, at the GP surgery and at home: this is how hypertension is diagnosed, not by a blood test.
- A cholesterol test (lipid profile) (LDL, HDL, triglycerides), plus lipoprotein(a) at least once in your life.
- Creatinine and eGFR to check the kidneys, which high blood pressure can damage.
- Fasting glucose or HbA1c, since diabetes multiplies heart risk.
- hs-CRP in some cases, to gauge inflammation.
- A full blood count, which describes the red blood cells that hold most blood NAD.
If you are curious about "biological age" tests, our guide on biological vs. chronological age explains what they can and cannot tell you.
Recent scientific advances
The big change in 2026 is that two large, independent teams measured NAD carefully in thousands of blood samples and reached the same conclusion: blood NAD does not quietly drain away as healthy people get older. That takes the wind out of the idea that everyone over 40 needs an NAD booster. At the same time, the Vilnius data hint that NAD may say something about the health of the heart and blood vessels, which researchers now want to test in studies that follow people over time.
Supplement trials are moving in the same cautious direction. Precursors such as NR reliably raise NAD in the blood, but so far that rise has not translated into clear benefits for blood pressure, memory or metabolism in most trials. For readers, the practical message is simple: rely on proven heart checks, and treat NAD testing and boosters as research topics for now.
When to see a doctor
- Your blood pressure readings are repeatedly 130/80 mmHg or higher.
- You have chest pain, shortness of breath, palpitations or swollen legs.
- You take NAD, NR or NMN products and also take heart or blood pressure medication.
- You have been offered an NAD blood test or IV drip and want to know whether it is useful for you.
Call 999 for chest pain that lasts more than a few minutes, sudden weakness on one side, or difficulty speaking.
Glossary
- NAD (nicotinamide adenine dinucleotide): a molecule found in every cell that helps turn food into energy and repair DNA.
- NAD precursor: a compound the body converts into NAD, such as niacin (vitamin B3), nicotinamide riboside (NR) or NMN.
- Whole blood: blood with all its cells, including red blood cells, rather than serum or plasma alone.
- Dried blood spot: a few drops of blood from a finger prick, dried on a card and analysed in a lab.
- Biomarker: a measurable value in the body that reflects a state of health or disease.
- Hypertension: blood pressure that stays too high, a major cause of heart attack, stroke and kidney damage.
FAQ
Do NAD levels decline with age?
In whole blood, two large 2026 studies found no decline in healthy adults. Tissue levels may behave differently, and that question is still open.
Is low NAD a sign of heart disease?
People with cardiovascular disease and hypertension had lower blood NAD, but the study shows a link, not a cause. NAD is not used to diagnose heart disease.
Should I get an NAD blood test?
For now, it has no established role in routine care and no clinical reference range. Standard tests such as a cholesterol test, glucose and kidney function are more useful.
Do NAD supplements lower blood pressure?
Trials so far show small or no effects. NR combined with exercise did not lower daytime blood pressure more than exercise alone in older adults with hypertension.
Are IV NAD drips safe?
Evidence is limited to small studies. Reported side effects include nausea, cramping, flushing and chest discomfort, and long-term safety is unknown.
Sources
- Romenskaja-Avgul D, et al. Whole-blood NAD levels track cardiovascular disease but not chronological age. Nature Metabolism, 2026. DOI: 10.1038/s42255-026-01660-3
- Trętowicz MM, et al. Human whole-blood NAD levels do not vary with age or lifestyle interventions. Nature Metabolism, 2026. DOI: 10.1038/s42255-026-01537-5
- Lin Y, et al. Nicotinamide riboside combined with exercise to treat hypertension in middle-aged and older adults: a pilot randomized clinical trial. GeroScience, 2025. DOI: 10.1007/s11357-025-01815-2
- Martens CR, et al. A phase-II randomized controlled pilot study of nicotinamide riboside supplementation in older adults with amnestic mild cognitive impairment. Alzheimer's & Dementia, 2026. DOI: 10.1002/alz.71605
- Yang W, et al. Safety and metabolism-related outcomes of oral nicotinamide mononucleotide supplementation in adults: a systematic review and meta-analysis. Nutrients, 2026. DOI: 10.3390/nu18142251
- Zhang M, et al. Effects of nicotinamide mononucleotide supplementation on blood pressure: a systematic review and meta-analysis of randomized controlled trials. Nutrients, 2026. DOI: 10.3390/nu18060890
- Alangari A, et al. Narrative review of intravenous NAD and NAD precursors in wellness and translational medicine. Frontiers in Aging, 2026. DOI: 10.3389/fragi.2026.1887175
- Managed Healthcare Executive. Low blood NAD levels track heart disease and hypertension, not aging. November 2026
- National Heart, Lung, and Blood Institute (NIH). High Blood Pressure
- U.S. Food and Drug Administration. Dietary Supplements
Other articles
- C3 complement blood test, ageing and inflammation
- Lymphocytes and ageing
- Lipoprotein(a) screening
- BNP, the cardiac blood marker
- Biological vs. chronological age
Understand your own blood test results with AI DiagMe
Lipids, glucose, kidney function, blood count: upload your lab report and AI DiagMe explains each value in plain language, flags what deserves attention and helps you prepare questions for your GP.
