NADH and NAD+ — the difference, the claimed benefits and the contraindications

The confusion is understandable: NAD and NADH are spelled almost the same and are sold as different products. The difference between them is simple and worth understanding, because it changes the way you look at the label.

The same molecule, two states

NAD+ is the oxidised form. NADH is the reduced form — that is, the same molecule after it has taken up electrons.

In the cell, the two are continuously converted into each other:

• NAD+ takes up electrons in the reactions that break down nutrients and becomes NADH;
• NADH hands the electrons over in the mitochondrial respiratory chain and becomes NAD+ again.

So they are not rival substances. They are the same coin, on its two sides. What matters biologically is not the amount of one of them, but the ratio between them — a ratio the cell regulates tightly, depending on what it has to do.

What this means for what you buy

The selling point of NADH products is that it is supposedly "the active form". That is a simplification. Both forms are active, in different roles; the cell does not need more NADH in general, but the right ratio at the right moment.

What can be said about oral NADH supplementation: it is an unstable molecule, sensitive to stomach acid, and its bioavailability is a matter of debate. Human studies exist, but they are few and small.

The benefits attributed to it

Most often: energy, less tiredness, cognitive function. The areas in which NADH has actually been studied are chronic fatigue and some neurological conditions — with small studies and inconclusive results.

The honest wording is the same as for NAD+: a clear biochemical role, limited clinical evidence in humans. Anyone promising more is going beyond what is known.

What happens to the ratio with age

The argument "you need more NADH" runs into an interesting observation. A study that measured the NAD+ metabolome in the plasma of healthy adults of very different ages found that with age NAD+ falls, but the reduced form, NADH, rises.

What this means and what it does not:

• it does not show that NADH supplementation is harmful — the study did not test any supplementation;
• it is not proof of causation — it is a measurement at a single point in time, not a follow-up over time;
• it does show, however, that ageing, at least in plasma, does not look like a lack of NADH. So the idea that NADH is "the form you are short of" does not follow from the available data.

NAD+, NADH, NADP+, NMN, NR — a glossary for the label

Several similar names appear on the shelves. What each one is:

A useful detail when comparing: in reviews of human studies with compounds that raise NAD+, the ones studied most often are nicotinamide riboside (alone or combined with pterostilbene) and NMN — not NADH. That does not make NADH useless, but it means that the evidence base for it is thinner than for the precursors.

And for the precursors, even with more studies, the conclusion remains cautious: supplementation is safe and well tolerated, it can raise NAD+ and its metabolites in several tissues, but doses and durations vary widely from one study to another, and small study groups limit the interpretation of effects on body functions. The detailed comparison: NMN or NAD+.

Contraindications and precautions

For oral NADH supplements, the usual precautions are:

• pregnancy and breastfeeding — safety data are lacking, so it is not recommended;
• liver or kidney disease — metabolism and elimination are affected, and the decision rests with your treating doctor;
• long-term medication — any supplement should be discussed with the doctor who prescribed it, not added on top of it on your own initiative;
• hypersensitivity to any of the components.

For intravenous administration of NAD+, the contraindications we check are pregnancy and breastfeeding, severe kidney failure, known allergies to the components and severe active infections.

One point that matters: "natural" does not mean "free of contraindications". A molecule the body produces itself may not be suitable when given from outside, in a particular clinical situation.

Reactions during a NAD+ IV drip

Contraindications say who should not have the IV drip. There is another question, for those who do: what may come up along the way.

A retrospective analysis published in 2026 compared 500 mg NAD+ infusions with nicotinamide riboside infusions, given in a commercial setting. With NAD+, moderate to severe digestive symptoms, a rise in heart rate and chest pressure were reported during the infusion. All of them disappeared once administration ended, and because of them the NAD+ infusions had to run more slowly — 97 minutes on average. The analysis is preliminary, and the authors worked for the network that gave the infusions.

The practical conclusion is the same one we apply ourselves: the slow rate is not a whim, and an unpleasant sensation should be reported immediately, because it is usually resolved by slowing down.

What we check at the assessment, before NAD+

The assessment is not a form with boxes ticked. Concretely, we discuss:

Your medical history — including kidney, heart or cancer conditions, which call for an individual decision.

The medication you take and your supplements, including those with NAD+ precursors.

Pregnancy or breastfeeding — a contraindication for the IV drip.

Known allergies and reactions you have had to other infusions.

Active infections — a severe active infection is a contraindication.

What you expect from the IV drip — if the reason is persistent, unexplained tiredness, the right conversation is about investigating it, not about NAD+.

If you have recent blood tests or medical letters, it helps to have them at the assessment. On how we approach IV drip safety in general: IV drip safety.

What we do at Synerva

We give NAD+ intravenously, not oral NADH. The dose and whether it is appropriate are decided at the medical assessment — including the decision that the protocol is not right for you, which is a legitimate outcome of an assessment.

What the molecule is: NAD+ — what it is and where the evidence stops. What supplements contain: NAD supplements or IV drip. The protocol: NAD+ IV drip.

Sources

Extension of use of nicotinamide riboside chloride as a novel food — EFSA Journal — bioavailability and safety data for NAD+ precursors.

Safety of beta-nicotinamide mononucleotide — EFSA Journal, 2026 — including the populations to which the assessment does not apply.

Clement et al., Rejuvenation Research, 2019 — NAD+ falls and NADH rises with age in the plasma of healthy adults; the role of the NAD+/NADH and NADP+/NADPH ratios.

Freeberg et al., Journals of Gerontology Series A, 2023 — review of supplements that raise NAD+ in humans: the most-studied compounds and the limitations of the studies.

Reyna et al., Frontiers in Aging, 2026 — reactions during NAD+ infusions compared with nicotinamide riboside, retrospective analysis.

For information only. Contraindications are checked at the medical assessment, not from a general list.