A weekly health led newsletter grounded in evidence-based medicine along with prospective randomized controlled trials (RCTs) by medical specialists. Our goal is to help you make sense of complex scientific information and turn it into clear, evidenced based practices you can use to make better decisions about your health and wellness.

In the commercial wellness setting, an NAD+ infusion is typically 500 milligrams.

It takes about an hour and a half, mostly because going faster gives people chest pressure and stomach cramps.

There is exactly one randomized controlled trial that has given people intravenous NAD+ and measured whether they actually got better.

That trial worked. Which is why the gap between those two numbers is the most useful thing in this field.

The molecule does plenty. The industry selling it is measuring the wrong thing.

MEDICAL TREND SNAPSHOT

CLINICAL BREAKDOWN

NAD+ holds two jobs. Almost every article about it describes only the first.

Job one is carrying electrons through energy production. The molecule flips between NAD+ and NADH millions of times and survives every round.

Job two is where aging biology lives.

Three enzyme families use NAD+ as raw material and destroy it in the process. Sirtuins run mitochondrial and epigenetic housekeeping. PARPs repair damaged DNA. CD38 handles calcium and immune signaling.

Every DNA repair event costs your cell real molecules of NAD+.

They get shredded, and the leftover nicotinamide has to be rebuilt from scratch through the salvage pathway.

That rebuild runs through one enzyme, NAMPT, which sets the speed limit for the entire loop.

Here is the part that matters. A cell under heavy repair load can be cycling enormous quantities of NAD+ while its measured concentration sits perfectly still.

Destruction and reconstruction cancel out. The level tells you nothing about the traffic.

THE EVIDENCE

The claim that NAD+ collapses by middle age traces mostly to one study from 2012.

Hassina Massudi and colleagues at the University of New South Wales measured NAD+ in human pelvic skin across a full age range.

The correlation was strong and negative. NAD+ fell as age climbed, and PARP activity rose in step, which fits the theory neatly.

Then a group at Amsterdam UMC did something nobody had done properly.

Maria Tretowicz and colleagues measured whole-blood NAD+ across seven independent human cohorts using validated mass spectrometry.

Blood NAD+ did not decline with age. It held steady across lifestyle interventions too.

It did rise when people took nicotinamide riboside, which tells you the assay was working perfectly well.

Both findings are correct. The reason they disagree is anatomical.

Blood is a buffered transport pool your body works hard to keep stable. Skin, muscle and brain are consumption tissue, where the enzymes that shred NAD+ actually live.

THE CENTREPIECE

In 2021, Samuel Klein's group at Washington University published the trial that still anchors this field.

Twenty-five postmenopausal women with prediabetes took 250 milligrams of NMN daily for ten weeks.

Insulin-stimulated glucose disposal rose 25 percent against a placebo that did not move.

That was the primary endpoint, set in advance, measured by clamp. This is about as clean as nutrition science gets.

The NIH compared the size of that improvement to losing roughly ten percent of your body weight.

For a capsule taken daily for ten weeks, that is a serious result.

Now the finding that got buried.

What did change were the NAD+ breakdown products, which is the fingerprint of a pathway running faster rather than filling up.

Set that against a Danish trial where 40 obese, insulin-resistant men took 2,000 milligrams of nicotinamide riboside daily for twelve weeks.

Eight times the dose. Blood NAD+ climbed. Insulin sensitivity did not budge.

One trial raised the number and got nothing. The other got a real result without raising the number.

Any product sold on the promise of raising your NAD+ level is selling you the reading rather than the mechanism.

The useful implication is not cynical. If the benefit comes from turnover, then it should show up wherever turnover is already under strain.

That is exactly the pattern the trials show.

THE ROUTE QUESTION

The molecule is large and carries two negative charges, so it cannot simply drift inside.

The route most cell studies describe is extracellular chopping by the enzyme CD73 into NMN, then into NR, which slips through nucleoside transporters.

Whether some NAD+ also crosses intact is still genuinely argued over in the literature.

Either way, what reaches your cells is precursors. The same class of molecule sold in a capsule.

An infusion changes how fast the precursor arrives. It does not change what the cell finally takes in.

Underneath the injectable pitch sits a quieter assumption, which is that a capsule cannot reach the tissues that matter.

A team in Bergen tested exactly that.

Brage Brakedal and colleagues gave newly diagnosed Parkinson's patients oral nicotinamide riboside for a month, then measured NAD+ inside the brain by phosphorus magnetic resonance spectroscopy.

The response varied widely, and three participants showed no brain response despite clear changes in blood and muscle.

That variation is a finding, not a failure. It says who responds is a biological question somebody can now go and answer.

So what about the needle itself?

In February 2026, Cory Gallagher and Owoturo Oluwaseun Emmanuel reviewed 113 studies, 33 of them in humans and 28 randomized. For intravenous or intramuscular NAD+ used for anti-aging or wellness, they found no eligible outcome trials.

Which brings us back to the trial from the opening, and it deserves respect.

Xiaofan Yu and colleagues randomized 180 adults with heart failure to intravenous NAD+ or placebo for seven days, on top of standard therapy.

A proper trial, a hard endpoint, a real result. In cardiac patients, in hospital, at 10 milligrams a day.

That is a fiftieth of a dose documented in a commercial setting, for a diagnosed heart condition rather than for aging.

The evidence for injected NAD+ exists. It points somewhere specific, and that place is a cardiology ward.

THE PROTOCOL

Start from what is established, because it is more than most people assume.

That is a real foundation. Five decisions follow from it.

READER PULSE

The only randomized trial of infused NAD+ that measured a real clinical outcome used a dose fifty times smaller than a wellness drip, in heart patients.

THE BOTTOM LINE

The six claims folded into every NAD+ advertisement are separate claims, and they hold up unevenly.

NAD+ matters. Precursors get absorbed. Blood levels rise. All established, all worth knowing.

Past that point the evidence gets specific about who benefits and how it is delivered. Specific is not the same as weak.

The field is not short of promise. It is short of people willing to say which link they are selling you.

This is health journalism, not medical advice. These are prescription medicines with real side effects, and in SELECT 16.6 percent of participants stopped treatment because of them against 8.2 percent on placebo. Decisions about starting, continuing or stopping belong with your own clinician.