WHAT PEOPLE AND MICE SHOWED
What NAD+ studies changed—and what they didn't
People who took two pill ingredients had a higher NAD+ reading. Small IV studies leave much more unknown, and mouse findings aren't human proof.
The clearest result from the studies
Human trials drew blood after people took two pill ingredients. They're called NMN and NR, and your body uses them to make NAD+. Both raised the blood reading. Cells need NAD+ to draw energy from a meal. Here's the limit I'd remember for you: one blood change can't show that you'll feel better or stay well, and the smaller shot and IV studies leave even more unknown for your care. If you asked where I'd begin, I'd choose the human blood results.
Those results are clear. Their meaning for daily health isn't.
How your body makes NAD+ from smaller parts
Your body can build NAD+ by three main routes. The busiest one saves used parts and builds them again [5]. Another starts with the pill ingredient NR and changes it into NMN before making NAD+ [5]. A third starts with a vitamin or a protein part found in food [5].
That work inside you explains many pills on store shelves. The two pill ingredients are small enough to enter your body and be rebuilt. Whole NAD+ doesn't cross freely into cells. In mice, gut bacteria helped change one pill ingredient into parts the animals could use [11]. Keep the limit in mind for your choice. A mouse result can't answer what happens in you. It isn't human proof.
What changed in aging mice as NAD+ fell
NAD+ gets used by helper proteins as cells manage strain or mend DNA [5]. You don't need their lab names to make a choice. What matters is that your supply can fall while those proteins work.
The clearest age finding came from mice. As the mice aged, one of those proteins rose while NAD+ fell across their body. Mice bred without that working protein held on to more NAD+, and their cells made energy better [2]. A review linked lower NAD+ with poor health in yeast, worms, and mice, with some work in people [5]. The mouse study gives you one possible cause. It isn't a forecast for you and doesn't prove that treatment will help.
What NAD+ changed in human trials
The strongest work checked blood or muscle in people. Women who had gone through menopause and had prediabetes received the pill ingredient NMN for 10 weeks at 250 mg/day. Their muscle responded better to insulin, the hormone that lowers sugar in your blood. Their weight, fat, muscle, and long-term blood sugar reading didn't change [1].
Healthy middle-aged adults received 300-900 mg/day for 60 days. More NMN brought more blood NAD+. Their six-minute walk covered more ground, and their own well-being scores rose. The authors favored 600 mg/day within that trial and saw no safety problem [3]. Healthy adults with excess weight received the pill ingredient NR at 100-1000 mg/day for 8 weeks. Their blood readings rose by 22%, 51%, and 142%. LDL, the type called bad cholesterol, stayed level. Blood signs tied to vitamin use didn't worsen either [4]. Group averages can't predict your response. They also can't replace your doctor, who knows your illnesses, pills, and reason for asking.
A 2025 Nature Metabolism review drew a firm line. Few human studies have tracked a steady fall with age, and lasting health gains still lack solid proof [14]. Pills changed blood. They didn't cure or reverse disease.
What one pill ingredient changes before NAD+
Your cells need one more step to make NAD+ from the pill ingredient NMN. In the best-known trial, women with prediabetes received 250 mg/day. Insulin then worked better in their muscle [1]. Another trial used 300/600/900 mg/day. Blood NAD+ was higher for every group on days 30 and 60. The researchers believed the rise was real, not a fluke. A test that estimates wear linked to aging stayed steady during the 60 days; a rise would have meant more wear [3].
Mice gave a separate finding. When scientists blocked the way mouse eyes make NAD+, NMN kept light-sensing cells alive [10]. That shows NAD+ mattered in those mouse eyes. It doesn't show that NMN protects your sight. There's no sight treatment result here.
United States sellers dispute NMN's legal status. The FDA says earlier drug study keeps NMN outside the dietary-supplement label. That's a dispute over the sales label, not proof of harm or a safety ban [14].
What the other pill ingredient changed
NR is short for nicotinamide riboside, a vitamin your body uses. Your cells can turn NR into NMN, then make NAD+. One human trial assigned 100, 300, or 1000 mg/day for 8 weeks. Blood readings rose by 22%, 51%, and 142%. They stayed up until the trial ended. Side effects matched those in people given a placebo, an inactive pill made for comparison. Volunteers didn't have flushing or higher LDL cholesterol. Blood signs tied to vitamin use didn't worsen [4].
A separate study exposed mice to loud noise. NR protected tiny links in the inner ear and helped their hearing return [13]. Because those were mice, your hearing may not respond the same way. Old clinic records found that people getting NR by IV had milder problems and shorter visits than those getting NAD+ [15]. See that IV comparison here.
What skin studies found with nicotinamide and NAD+
Niacinamide is a vitamin used in some skin creams. It also helps your cells refill NAD+. Most skin studies put the cream right on the skin. A review found that signs of aging and dark patches grew more slowly in human trials. People had few problems with the cream [12]. The cream may help your skin hold water and protect itself. That doesn't show that pills or IV NAD+ make your whole body younger. A skin result doesn't cover a drip.
What changes between NAD+ and NMN
Don't treat NAD+ and NMN as the same substance. NAD+ does the cell work. NMN supplies material that a cell can rebuild as NAD+ [5]. Whole NAD+ crosses the gut and cell walls poorly. Smaller NMN can enter, then change inside. An NMN pill trial therefore shows its effect on your blood reading [1][3]. It can't show what a swallowed NAD+ pill would do. Remember the split when you look at a store label.
What IV NAD+ changed—and why proof is weak
Human proof isn't strong for IV NAD+. A small study ran 750 mg over 6 hours in healthy men. For about the first 2 hours, their blood showed no whole NAD+. Broken-down parts rose in urine instead. At faster flow, men reported mild chest tightness and belly pain [6].
A second small study used five daily drips of 750 mg. Its group improved on 6 of 8 thinking tests, versus 2 of 8 with salt water [9]. Another paper covered 50 people after other care for drug-use illness had failed. The care paired IV NAD+ with a drug that helps natural brain chemicals last longer. The scores fell for craving, worry, and low mood. The authors said those drops were unlikely to be a fluke, but there was no fair comparison group [7]. A review cited a 1961 report of 104+ people. It still called IV NAD+ unapproved and asked for fair trials [8]. You don't have settled proof here.