You've settled on NAD+, or you're already taking it, and now every thread you open tells you it works better with something else. Usually the something else is whatever the person posting also bought.
Some of those pairings have a real rationale. Some are two things that happen to be popular at the same time. Here's how to tell them apart, and the one decision that matters more than which combination you land on.
The unglamorous answer first: run it alone
For the first couple of months, take NAD+ and nothing else new.
This isn't caution for its own sake, it's arithmetic. If you start two things in the same month and something shifts, you have no idea which one moved it, so you keep buying both indefinitely just in case. If nothing shifts, you've spent double to learn one thing. Eight to twelve weeks on its own, changing nothing else major, and you end up with an answer you can actually use.
Everything below is about what earns the second slot.
If your real goal is energy, look at the mitochondrial pair
NAD+ is the cofactor your cells use to turn fuel into usable energy. The compounds people logically pair with it work on the machinery that spends it, which is why this combination gets suggested more than any other.
The honest version: NAD+ raises the supply, SS-31 and urolithin A are studied for the condition of the mitochondria doing the spending. That's a coherent story, and it's still a story rather than a finding, because nobody has run the trial that tests the combination in people like you. Worth knowing before you pay for two things instead of one.
If you want to go this way, read what order actually makes sense first. It exists precisely because these three get bought together and shouldn't be started together.
If your real goal is skin, NAD+ isn't the lead
A lot of women arrive at NAD+ through anti-aging content and are actually thinking about skin. If that's you, the pairing question is upside down: GHK-Cu has the more direct skin research behind it, and NAD+ is the general-systems compound sitting alongside it.
Nothing wrong with running both eventually. But if skin is what you'd notice and what you'd judge it by, starting with the one aimed at skin gives you a cleaner read.
If sleep is the actual problem, be careful here
The growth hormone peptides get folded into NAD+ conversations constantly, usually by someone who felt better on both. The mechanism is different, hormonal rather than metabolic, and "I have more energy" is the most common subjective report on that whole class, which makes it the hardest kind of evidence to trust.
If broken sleep is the thing actually flattening you, that's its own question and it's covered in peptides for sleep. Adding a growth hormone peptide to NAD+ to fix sleep is solving the second problem first.
The oral question, which is really a pairing question
People often ask whether to add an oral precursor like NMN to injectable NAD+. That isn't a stack, it's the same target approached two ways, and it comes down to the unsettled argument about whether raising what's circulating raises what's inside your cells.
We've put the two side by side in NAD+ versus NMN, and the broader picture of what the anti-aging research does and doesn't claim is in the midlife energy question. Running both at once mostly buys you a more expensive version of one experiment.
What two things actually cost
Before committing to a pairing, do the arithmetic on both at once, per milligram, for a realistic run rather than a single vial. Combinations get sold on the strength of the story and bought on the assumption that the second compound is a small addition, and it usually isn't.
Run each through the price comparison and check the spread. And whichever you add, the same rule holds as for the first one: buy from someone who publishes third party testing. Our vendor directory notes who does.
Where to go from here
If you're building a broader routine rather than choosing one pairing, the longevity and anti-aging stacks women ask about most covers the combinations in full, including the ones NAD+ isn't part of.
And if you haven't bought anything yet, where to start with peptides is the better first read, because sequencing decisions are much easier before you own three vials.