NAD+: what it does, what was tested, and what isn't known

What do you need to know first?

Inside every cell, NAD+ helps turn food into energy. It isn't a drug. Your body already makes it, and stores sell supplements rather than an approved medicine. Pills tend to carry NMN or NR, smaller parts from which your body can build NAD+. The gut takes in little NAD+ itself.

Scientists know that both pills often raise blood NAD+, but they don't know whether a higher blood number helps a person feel better, stay well, or live longer.

This page walks you through what has been found.

What does NAD+ do inside your body?

NAD+ has two main jobs. First, it helps your cells draw useful energy from food ^[13]. NAD+ changes form while helping cells with energy. Then it changes back, ready to help again ^[13].

The second job is repair and control. Enzymes are proteins that do set jobs inside a cell; some use NAD+ while they mend DNA, while others help control which cell instructions are active or calm swelling ^[5].

The amount of NAD+ in organs and other body tissue doesn't stay level. In mice and people, the amount tends to fall with age ^[2]. One reason may be that an enzyme uses more NAD+ later in life ^[5]. That leaves less for other jobs.

This drop gave scientists a fair question. Does raising NAD+ help people, or does it only change a blood-test number? The answer is still open.

What does a NAD+ supplement really contain?

Many products sold as NAD+ supplements contain little usable NAD+ itself. Your gut has trouble taking it in. Pills often contain NMN or NR instead. Your cells use those smaller parts to make NAD+ ^[5]. Niacin and another form of vitamin B3 can help your body make it too ^[5].

In one human study, adults carrying extra weight took NR each day, and after eight weeks, amounts of 100, 300, and 1000 mg/day raised blood NAD+ by 22%, 51%, and 142%, in that order. The other group received pills with the same appearance but without NR. Those were the placebo pills. Both groups reported side effects at about the same rate. No one reported flushing ^[4].

In another study, people took NMN at 300, 600, and 900 mg/day for 60 days. Their blood NAD+ was higher than with a placebo on days 30 and 60 ^[3].

Both studies found a higher blood-test number. Neither result proves that a pill prevents or treats disease. The FDA, the agency that oversees drugs, hasn't approved either pill as a drug. None of those study amounts tells you what to take.

What is an NAD+ precursor?

An NAD+ precursor is a building block your body uses to make NAD+. Your body turns NR into NMN and then turns NMN into NAD+ ^[5]. That is why NMN is called one step closer. Being closer isn't proof that NMN works better. Niacin and another form of vitamin B3 reach NAD+ by other steps ^[5].

A bottle may say that it helps raise NAD+. The pill usually holds one of these building blocks, not NAD+ itself. Your gut can take in the smaller part more easily.

The NMN and NR page lays out the human results for both.

Which page answers your next NAD+ question?

For the age question, read why NAD+ falls over time. For heart and blood pressure, go to what heart studies found. NMN and NR are compared here. The dose page reports only study amounts; it doesn't choose one for you. The FAQ covers side effects seen in tests, and the reference page names every paper.

A 2025 review keeps the subject in bounds. The reviewers saw that NMN and NR often raise blood NAD+. They also found too little proof that either one prevents illness or helps people live longer ^[15].

Start with the question that matters to you.

Why do people take an NAD supplement?

In every cell, your body makes NAD+. Stores sell NMN and NR as an NAD supplement because both can raise blood NAD+ ^[4][1]. People hope this may help energy, muscle, or heart health. Human tests have not found that either one treats or prevents a disease. Neither is an approved drug.

What work does NAD+ do in your cells?

NAD+ helps your cells draw energy from the food you eat ^[13]. Cells also use it while mending DNA and controlling swelling ^[5]. The amount in body tissue often falls with age ^[2]. That is why scientists test NMN and NR. A lower amount alone cannot prove that a pill will improve your health.

How is NAD+ different from vitamin B3?

NAD+ is not vitamin B3. Niacin and another form of vitamin B3 are building blocks for NAD+. Two more building blocks are NMN and NR. Your body can use all four to make NAD+ by different steps ^[5]. Each helps make NAD+, but the four still differ.

Is NAD+ a peptide?

No. Two joined cell parts make NAD+. Protein is built from small pieces called amino acids. Several amino acids linked in a row form a peptide. NAD+ belongs to neither group ^[13].

What do the letters NAD stand for?

The letters NAD stand for nicotinamide adenine dinucleotide, the lab name for one vitamin form joined with two small cell parts ^[13]. When NAD is ready to help draw energy from food, the lab adds a plus sign. The substance then changes form and changes back.

What can NAD mean on a medical chart?

Scientists use NAD as the name of the cell helper described here ^[13]. Cells use it while making energy and mending DNA ^[5]. On a medical chart, NAD can also mean "no acute distress." That means the person didn't look gravely ill at that moment. These pages use NAD for the cell helper.