NAD (NAD+) Test

Your cells run on a molecule called NAD+ (nicotinamide adenine dinucleotide), and they cannot function without it. NAD+ sits at the center of how your body turns food into energy, repairs damaged DNA, and keeps inflammation in check. When levels drop, those systems slow down, and the effects look a lot like aging: less energy, slower recovery, and a body that is less able to protect itself from disease.

What makes this test interesting for someone focused on prevention is that NAD+ decline appears to precede many of the conditions associated with getting older. Measuring it gives you a window into cellular health that no standard blood panel provides. This is still a research-stage marker without formal clinical cutpoints, so a single reading will not diagnose anything on its own. But establishing your baseline and watching the trend over time puts you ahead of the science as it matures.

What NAD+ Does in Your Body

NAD+ wears two hats. First, it shuttles electrons during the chemical reactions that convert glucose and fat into the energy currency your cells actually spend (a molecule called ATP). Without enough NAD+, that conversion slows down. You can think of NAD+ as the rechargeable battery that keeps the energy assembly line moving.

Second, NAD+ is consumed, literally used up, by enzymes that repair DNA damage, regulate gene expression, and control inflammation. The most important of these enzyme families are sirtuins (which silence harmful genes and regulate your internal clock) and PARPs (which patch broken DNA strands). Every time one of these enzymes does its job, it breaks apart an NAD+ molecule in the process. Your body must constantly rebuild its NAD+ supply to keep pace.

Every cell makes NAD+, but the rate varies by tissue. The heart, with its relentless metabolic demand, maintains the highest concentrations. The liver produces NAD+ from the amino acid tryptophan through a dedicated pathway and then exports a building block called nicotinamide to other organs, which recycle it back into NAD+ through a shortcut known as the salvage pathway.

Why NAD+ Declines With Age

NAD+ levels fall as you get older, and the decline is not subtle. In human skin tissue, NAD+ shows a strong negative correlation with age in both men (r = -0.706) and women (r = -0.537). The cause is a double hit: your body makes less NAD+ because the key recycling enzyme (called NAMPT) becomes less active, and at the same time, NAD+ gets consumed faster because enzymes that respond to DNA damage and chronic inflammation ramp up their activity.

One enzyme in particular, CD38, appears to be a major driver. CD38 levels rise with age and with chronic low-grade inflammation, and it chews through NAD+ at a high rate. The result is a widening gap between supply and demand that touches nearly every organ system.

Heart Disease and Cardiovascular Risk

The heart is especially vulnerable to falling NAD+ because it is the most metabolically active organ in the body. In one study, patients with moderate to severe heart failure had whole blood NAD+ of just 13 micromoles per liter (a unit measuring very small concentrations in blood), compared to 18 micromoles per liter in healthy controls. Elderly patients hospitalized for heart failure also had significantly lower whole blood NAD+ than age-matched healthy donors.

NAD+ depletion in blood vessel walls contributes to stiffening of the arteries, impaired ability of vessels to relax, and elevated blood pressure. Early human trials of NAD+ precursor supplements have shown modest improvements in blood pressure and markers of arterial stiffness, though large randomized trials confirming cardiovascular benefit are still needed.

Metabolic Health and Diabetes

The relationship between NAD+ and metabolic disease is more nuanced than you might expect. A community study of 1,394 adults in the Jidong cohort found that people in the highest NAD+ quartile (above 37.8 micromoles per liter) actually had about three times the odds of having metabolic disease compared to those in the lowest quartile (at or below 29.4 micromoles per liter), after adjusting for standard risk factors.

This seemingly paradoxical finding, with higher NAD+ linked to worse metabolic health in a snapshot, may reflect the body's compensatory response: cells ramp up NAD+ production when metabolic stress is already underway. This is a cross-sectional association (a single-time-point comparison, not a study that followed people forward in time), so it cannot tell us whether high NAD+ caused the metabolic problems or was the body's attempt to fight them. It does mean that interpreting a single NAD+ reading requires context, not just a simple "higher is better" rule.

Neurological Health

NAD+ depletion has been linked to several neurodegenerative conditions in laboratory and animal research, including Alzheimer's disease, Parkinson's disease, and damage from reduced blood flow to the brain. In human studies, patients with demyelinating neurological diseases (conditions where the protective coating around nerve fibers is damaged) had whole blood NAD+ of about 14 micromoles per liter, significantly lower than the 18 micromoles per liter seen in healthy controls.

A study of cerebrospinal fluid (the liquid surrounding the brain and spinal cord) found that participants over age 45 had lower NAD levels, and drinking more than one standard alcoholic drink per day was associated with even lower levels. While these findings are preliminary and cannot prove that low NAD+ causes neurological disease, they suggest the brain is sensitive to shifts in NAD+ availability.

Sex and Age Patterns

Men and women show different NAD+ trajectories. In the largest population study (1,518 adults from the Jidong community), men had higher whole blood NAD+ than women (34.5 vs. 31.3 micromoles per liter). Men showed a clear decline after age 60, while women's levels remained relatively stable across age groups. A separate study of plasma NAD+ found that women had higher ratios of the active form (NAD+) to the spent form (NADH), but this advantage narrowed with markers of biological aging like arterial stiffness.

These sex-based differences mean that a "normal" NAD+ reading may look different for men and women, and the trajectory of decline may matter more for men, particularly after midlife.

Reference Values From Research

No medical society has published standardized clinical reference ranges for NAD+. The values below come from population studies and should be treated as research-derived orientation points, not diagnostic cutoffs. Different labs use different assay methods, so the absolute numbers can vary significantly depending on which technique and sample type your lab uses.

Notice the wide spread: the same molecule measured in whole blood ranges from a median of 18 to a mean of 33 across different studies, depending on the assay. This is why comparing your result to someone else's number, or to a range from a different lab, is unreliable. The most useful comparison is always your own result over time, measured by the same lab using the same method.

When Results Can Be Misleading

NAD+ measurement is technically demanding, and several factors can distort a single reading enough to lead you to the wrong conclusion. The biggest source of error is how the sample is handled after it leaves your arm. NAD+ inside your cells is about 500 times more concentrated than NAD+ floating freely in your plasma. If even a small number of cells rupture during collection or processing, the released intracellular NAD+ can artificially inflate the plasma reading. Prolonged centrifugation (spinning the sample for more than five minutes) and certain braking speeds on the centrifuge have been shown to affect results.

Acute inflammation also shifts NAD+ levels. Plasma NAD+ correlates negatively with C-reactive protein (a marker of inflammation), so an infection, surgery, or even a significant injury in the days before your blood draw could temporarily suppress your reading. Similarly, intense exercise boosts NAD+ metabolism in immune cells and muscle, meaning a hard workout the day before testing could produce a reading that does not reflect your true resting baseline.

One NMN supplementation trial reported coefficients of variation (a measure of how much readings scatter around the average) of 29% to 113% across individuals. That level of variability means a single measurement is a rough sketch, not a photograph.

Tracking Your Trend

Given the variability between labs, between assay methods, and even between blood draws on different days, a single NAD+ measurement tells you relatively little. The real value comes from tracking your number over time using the same lab and the same method. One study found that individual NAD+ baselines remain stable over 100 days in people not making changes, which means that when your trend does shift, it likely reflects something real rather than random noise.

If you are getting a baseline: test twice, several weeks apart, and average the results to establish your starting point. If you are making changes (starting a supplement, changing your exercise routine, reducing alcohol), retest after 8 to 12 weeks to see whether the number has moved. After that, testing every 6 to 12 months lets you watch for age-related drift and confirm that whatever you are doing is still working.

Be precise about what you are tracking. If you start taking nicotinamide riboside (NR) or nicotinamide mononucleotide (NMN) and want to know whether it raised your NAD+, make sure the test you use actually measures NAD+ in whole blood, not a related molecule like nicotinamide. Most supplementation trials measured whole blood NAD+, so that is the best-validated matrix for monitoring a supplement response. If your lab measures something different (plasma NAD+, or a NAD metabolite), the supplement trial data may not directly apply to your result.