The obvious question once you start supplementing is whether you can measure the result. The short answer is that you can measure something, it is harder than it sounds, and for most people it is not yet worth the money.
The one-paragraph version
NAD+ can be measured accurately in a properly equipped laboratory. The obstacles are that it degrades fast once a sample leaves your body, that blood may not reflect the tissues you care about, and that there is no established reference range telling you what a given number means. A test can show you a number. It cannot yet tell you what to do differently.
How it is measured
| Method | What it does | Where it is used |
|---|---|---|
| LC-MS/MS | Separates and identifies molecules by mass; the reference approach | Research labs, better commercial testing |
| Enzymatic cycling assay | Amplifies a reaction to detect small amounts; cheaper | Common in commercial kits |
| HPLC | Separation by chemistry, without mass detection | Older lab workflows |
| 31-P magnetic resonance | Measures in living tissue, non-invasively | Research only; expensive, scarce |
That last row is the interesting one scientifically, because it measures NAD+ in tissue in a living person rather than in a tube. It is also confined to a small number of research centres and is not something you can book.
The problem nobody mentions: it does not keep
This is the practical obstacle that undermines most casual testing.
NAD+ begins degrading as soon as a blood sample is drawn. Enzymes in the sample keep working, and the molecule is not especially stable to begin with. Getting a trustworthy number requires rapid processing — chilling, separating and quenching the sample promptly — under a controlled protocol.
A sample that sits at room temperature, or travels through the post over a day or two, is not measuring your NAD+ level. It is measuring how long the sample spent in transit. Two tests of the same person handled differently can differ more than a year of supplementation would move the number.
Blood is not the tissue you care about
Even a perfectly handled sample has an interpretation problem.
Most accessible testing measures NAD+ in whole blood or in isolated blood cells. The tissues people actually care about — muscle, brain, liver — are not blood, and NAD+ levels and turnover differ between tissues. A rise in a blood marker is genuine evidence that something was absorbed and metabolised. It is weaker evidence about the tissue you were hoping to affect.
And there is no reference range
For a standard blood test, a result arrives next to a range derived from large populations, so you can tell whether a number is unusual. NAD+ has no established equivalent. There is no agreed figure for what a healthy forty-five-year-old should have, and no threshold above which benefits are known to appear.
Which means a result is a number without a verdict. You can compare it to your own earlier number, assuming identical handling both times. You cannot compare it to a standard, because there is not one.
So should you test?
Probably not yet, if the question is "is this working for me." The handling problem, the tissue problem and the missing reference range stack up, and the money is better spent on a longer, more consistent trial of the supplement itself.
Possibly, if you enjoy the data and you understand you are tracking a number with a wide error bar and no interpretive context. Some people find that motivating. That is a legitimate reason as long as it is the actual reason.
A more useful approach for most people is the structured self-assessment — defining what you expect to change before you start, then giving it long enough to tell signal from expectation.
Related: How long to trial it · Why NAD+ declines · CD38, the drain that grows