NAD+ vs NADH: What's the Difference?

NAD+ and NADH are the same coenzyme in two states: NAD+ is the oxidized form that picks up electrons, and NADH is the reduced form that carries them. Your cells turn one into the other constantly as they convert food into energy, so this is a loop, not a rivalry. On a supplement label, the "+" or the "H" tells you which form is in the bottle, not which one "works better." And in research papers, "NAD" often means both forms counted together.

NAD+ vs NADH: the short answer

Think of NAD+ as an empty shuttle and NADH as the same shuttle loaded with electrons. NAD+ fills up while your cells break down food; NADH unloads where your mitochondria make ATP and turns back into NAD+. Same molecule, two states, one cycle. For the bigger picture on the molecule itself, start with what NAD+ is and how it works.

Key takeaways

NAD+ is the oxidized form. NADH is NAD+ after it has accepted two electrons and a proton.
Cells cycle between them all day: NAD+ collects electrons from fuel, and NADH delivers them to the chain that makes ATP.
Both come from niacin (vitamin B3) and the amino acid tryptophan, not from vitamin B12.
Many studies report "NAD" as NAD+ plus NADH combined, so check what was measured before trusting a headline number.
Oral NAD+ has a five-day blood-marker trial. Oral NADH research comes mostly from trials in people with chronic fatigue syndrome (ME/CFS) who took it with CoQ10.

What is the difference between NAD+ and NADH?

Oxidized versus reduced. Whether you search NAD+ vs NADH or NADH vs NAD+, that is the whole difference. The free OpenStax Biology 2e textbook puts it plainly: NAD+ is the oxidized form of the molecule, and NADH is the reduced form after it has accepted two electrons and a proton. The name stands for nicotinamide adenine dinucleotide, and the textbook notes that it is derived from niacin, vitamin B3.

On paper, the gap looks tiny. PubChem lists NAD+ (also called nadide) as C₂₁H₂₇N₇O₁₄P₂ at 663.4 g/mol and NADH as C₂₁H₂₉N₇O₁₄P₂ at 665.4 g/mol. The two formulas sit two hydrogens apart because the database records each molecule in its electrically neutral form. The "+" in NAD+ marks a positive charge on its nicotinamide ring; once the ring takes on electrons, that charge disappears and the name picks up its "H."

So the plus sign is a charge, not a quality grade. Whatever the label's font size suggests, neither form is the "premium" edition.

What do NAD+ and NADH do in your cells?

They run your cells' energy relay. NIH's Office of Dietary Supplements (ODS) explains in its niacin fact sheet that NAD is mainly involved in the reactions that transfer the energy in carbohydrates, fats and proteins to ATP, the cell's primary energy currency. More than 400 enzymes need NAD, more than for any other vitamin-derived coenzyme. A 2018 review in Antioxidants & Redox Signaling by Xiao and colleagues describes how the cycle runs:

NAD+ collects electrons. As glucose and other fuels are broken down, first in glycolysis in the cell's cytoplasm and then in the TCA cycle inside mitochondria, NAD+ accepts electrons and becomes NADH. With plenty of oxygen, the mitochondria make eight NADH per glucose molecule: two as pyruvate is converted to acetyl CoA, and six in the TCA cycle itself (three per turn, two turns per glucose), as OpenStax Biology 2e lays out.
NADH delivers them. In the mitochondria, NADH hands its electrons to complex I of the electron transport chain and is oxidized back to NAD+. NADH made in the cytoplasm passes its electrons in through shuttle systems.
The electrons power ATP production. As electrons travel down the chain to oxygen, the chain pumps protons out of the mitochondrial matrix. That proton gradient drives ATP synthase, the enzyme that makes ATP.
NAD+ goes back for another load, and the cycle repeats.

NAD+, the oxidized form specifically, has a second job too. It is a raw material that some enzymes use up as they work: the Xiao review names the sirtuins, the PARPs and the CD38 family. ODS links NAD-dependent enzymes to maintaining genome integrity, controlling gene expression and cell communication.

Why does the NAD+/NADH ratio matter?

The ratio helps set a cell's redox state, the balance between its oxidizing and reducing power. The Xiao review calls the NAD+/NADH and NADP+/NADPH pairs essential for maintaining that balance and for regulating metabolism. It also notes that excess NADH and/or NADPH can lead to "reductive stress." More NADH is not automatically better; balance is the point.

Three things make the ratio hard to pin down:

It is split into compartments. The review describes NAD pools as highly compartmentalized, with separate pools in the cytoplasm and mitochondria; in one cultured human cell line, the review's estimates put the majority of the NAD+ in the mitochondria.
Most of it is bound. NAD and NADH are mostly attached to proteins inside the cell, and free molecules make up only a small share of the pool.
It differs by cell type. Red blood cells from healthy adults held 48 μM NAD+ and 1.4 μM NADH in measurements the review cites, roughly 34 to 1 (our arithmetic); other cells run different balances.

No supplement label can describe that balance, and the blood tests in the trials below don't measure it.

NAD+, NADH, NADP+ and NADPH at a glance

NAD has a sibling. Cells add a phosphate group to NAD+ to make NADP+, which forms its own oxidized and reduced pair. ODS describes the split neatly: NAD is mainly involved in breaking fuel down for energy, while NADP enables building reactions, such as making cholesterol and fatty acids, and plays a critical role in antioxidant defense.

NAD+, NADH, NADP+ and NADPH: state, main job and where each comes from
Form	State	Main job	Where it comes from
NAD+	Oxidized	Accepts electrons as carbohydrates, fats and proteins are broken down; also used up by sirtuins, PARPs and CD38-family enzymes	Niacin (vitamin B3), which all tissues convert to NAD, and the amino acid tryptophan
NADH	Reduced (carries two electrons and a proton)	Delivers electrons to complex I of the electron transport chain, which drives ATP production	NAD+, after it accepts electrons
NADP+	Oxidized	Partner in building and antioxidant reactions	NAD+ plus a phosphate (via NAD kinase), in all tissues except skeletal muscle
NADPH	Reduced	Supplies electrons for building molecules such as cholesterol and fatty acids, and for antioxidant defense, including recycling glutathione	NADP+, after it accepts electrons

Sources: the ODS niacin fact sheet, the Xiao 2018 review and OpenStax Biology 2e.

What "NAD" means in supplement studies

Often, it means NAD+ and NADH added together. Many lab tests measure total NAD, so a headline such as "NAD up 50%" can be counting both forms. Two trials show how.

In a 60-day trial published in GeroScience in 2023, 80 healthy middle-aged adults took 300, 600 or 900 mg of the NAD+ precursor NMN, or a placebo, each day. Researchers measured blood NAD "as the total 'NAD+ + NADH' concentration in serum." NAD rose in all three NMN groups compared with placebo, most at 600 and 900 mg.

A 2026 trial of an oral NAD+ powder, also in GeroScience, measured NAD inside blood cells (in whole blood) and NAD in plasma. The authors note that the assay "measures total NAD (NAD+ + NADH) rather than the NAD+/NADH ratio," and that if NADH rose too, "the functional redox implications would differ from a selective increase in oxidized NAD+."

None of this makes those results less real; it tells you what the number is. Before you lean on a headline figure, check three things: which molecule people took, what was sampled (serum, plasma or whole blood), and whether the test measured NAD+, NADH or both.

NAD+ vs NADH supplements: what has been studied?

Both forms have human data, from very different people and for very different questions.

Oral NAD+. The 2026 RENEWAL-NAD+ trial randomized 60 healthy adults aged 45 to 75 to a proprietary oral NAD+ powder (LNAD+) or a placebo for five days, with 50 in the main analysis. By day 6, NAD inside blood cells was 53% higher than placebo, while plasma NAD did not change. The powder was very well tolerated, with one mild case of nausea, and none of the secondary clinical, wellbeing or wearable measures held up after statistical correction. That inside-the-cell result is worth noticing, since ODS notes that NAD and NADP in food are converted to nicotinamide in the gut and then absorbed.

Oral NADH. The main human data come from people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) who took NADH together with coenzyme Q10. In an 8-week trial of 73 women published in 2015, 200 mg of CoQ10 plus 20 mg of NADH a day lowered fatigue-impact scores compared with placebo (p < 0.05). A larger 2021 trial with 207 patients used the same daily amounts for 8 weeks, with a follow-up visit 4 weeks later. The supplement group reported less cognitive fatigue and lower overall fatigue scores than at the start, although the two groups' fatigue scores moved largely in parallel. Both trials tested a combination, so neither can show what NADH does on its own.

Precursors. Much of the "NAD booster" research uses building blocks such as NMN and NR instead of NAD+ or NADH. For how that evidence stacks up, see what NAD+ research shows.

Reading a label? Look for the exact molecule (NAD+, NADH, NMN, NR or niacin), the amount per serving, and whether any study a brand cites used that same ingredient. A trial of 20 mg of NADH with CoQ10 can't stand in for an NAD+ product, or the reverse; borrowing results across molecules is supplement Mad Libs. Our guide to choosing an NAD+ supplement walks through the label checks in more detail.

Quick answers

Is NAD just vitamin B3 or B12?

Vitamin B3, not B12. Your body makes NAD from niacin (vitamin B3) and from some of the tryptophan in dietary protein. ODS gives the usual estimate as 1 mg of niacin from 60 mg of tryptophan, though the conversion varies a lot between people. Vitamin B12 is a different nutrient altogether: it contains the mineral cobalt, which is why its forms are called cobalamins. NAD's formula contains no cobalt at all.

What form of NAD is best?

There is no head-to-head trial comparing NAD+, NADH, NMN and NR capsules on health outcomes, so no form has an evidence-based crown. Choose by the molecule you want and a routine you will keep: an NAD+ capsule gives you the coenzyme itself, and if you are weighing a precursor, start with NMN vs NAD+.

Who shouldn't take NADH?

The evidence is limited: the NADH trials were short and done in people with ME/CFS. If you are pregnant or breastfeeding, take prescription medicines or manage a medical condition, check with a clinician before trying NADH or any NAD product. In the 2021 trial, no serious adverse events were reported, and dropouts for side effects such as upper-stomach pain and dizziness were similar in both groups (8 on the supplement, 11 on placebo). For NAD+ itself, see NAD+ side effects and safety.

Where Infinite Labs NAD+ fits

If NAD+ is the form you want, Infinite Labs NAD+ capsules are a strong pick for a simple daily routine. Each veggie capsule contains 500 mg of NAD+, the oxidized form, with 2.5 mg of BioPerine, a standardized black pepper extract, and every amount is disclosed on the label. Take one capsule daily with food, or as recommended by a qualified healthcare professional; each bottle holds 30 servings. The capsule shell is plant-based hypromellose, the flow aid is Nu-FLOW (made from rice hulls), and the formula is third-party tested and made in GMP-certified facilities.

Infinite Labs doesn't sell NADH, so there is no NAD+-or-NADH decision to make at checkout. The role of NAD+ in your cells is well established, and this capsule makes it an easy, consistent part of a routine built on food, movement and sleep: a steady daily habit, not a stimulant. Certificates of analysis are available on request.

The practical takeaway

NAD+ and NADH are one coenzyme in two states: NAD+ collects electrons, NADH carries them to where ATP is made, and cells recycle one into the other constantly.
The ratio between them is managed cell by cell and compartment by compartment. No label or single blood test describes it.
In studies, "NAD" often means NAD+ plus NADH. Check the molecule people took, what was sampled and what the test measured before you trust the headline.

The supplement aisle has more look-alike acronyms than a government org chart; for another one people mix up with NAD+, see NAC vs NAD+. If NAD+ itself is your pick, Infinite Labs NAD+ gives you 500 mg in one capsule a day, taken with food.

Sources

Educational information, not medical advice. Infinite Labs NAD+ is not intended to diagnose, treat, cure, or prevent any disease.