Of the two timing questions people ask — what time of day, and with or without food — one has a decent rationale behind it and one is mostly folklore.
Short version
Take it in the morning. There is a coherent circadian argument for it. Do not agonise over whether it is with food; the evidence is thin and the effect, if any, is small. Both questions are far less important than taking it at all, every day.
The morning argument, and it is a real one
NAD+ is not a flat line through the day. Its levels oscillate on a roughly 24-hour cycle, and the mechanism behind that is well characterised: the core circadian clock machinery regulates expression of NAMPT, the rate-limiting enzyme of the salvage pathway. More NAMPT means more recycling capacity.
The relationship runs in both directions, which is the interesting part. The clock controls NAMPT, NAMPT controls NAD+ availability, and NAD+ availability controls sirtuin activity — and sirtuins in turn feed back onto the clock machinery. It is a loop, not a one-way street.
The practical inference: supplying precursor during the active phase of that cycle, when recycling capacity is building rather than winding down, is more likely to be useful than supplying it as the system quiets down. For most people that means with or shortly after breakfast.
The evening case
Some people report that an evening dose disturbs their sleep, which is the most common practical reason given for avoiding it. Others report nothing at all. There is no strong published basis for either experience, and individual variation here seems large.
If you have tried evening dosing and slept badly, move it to the morning. That is a sufficient reason on its own and you do not need a study to justify it.
With or without food
This is where most of the confident internet advice outruns the data.
The fasted argument: an empty stomach means faster transit and less competition for absorption. The with-food argument: food slows transit and buffers stomach acid, which may protect the compound. Both are plausible. Neither has the human evidence to settle it for this compound class.
What we would actually do: take it with breakfast, because the single biggest predictor of whether you are still taking a supplement in six months is whether it is attached to something you already do every day without thinking. Anchoring a dose to an existing habit is worth more than any plausible absorption tweak.
A protocol you can actually run
| Decision | Our answer | Confidence |
|---|---|---|
| Time of day | Morning | Reasoned, not proven |
| With food | With breakfast, for adherence | Low — evidence is thin either way |
| Split or single dose | Single, unless the label says otherwise | Simplicity beats theory |
| Days per week | Seven | High — consistency is the variable |
| When to judge it | 90 days minimum | High |
How to assess it honestly
Before you start, write down two or three specific things you would expect to change — and make them concrete. "More energy" is unmeasurable and you will talk yourself into it. "I stop needing a mid-afternoon coffee" is something you can check.
Then wait the full ninety days. Expectation effects are strongest in the first few weeks, which is exactly when people decide whether something is working. Judging early is how you end up paying for a year of something that did nothing.
Related: Why oral is the default · Why NAD+ declines · All protocols