If you have been reading about NAD+ for energy, healthy ageing or general wellbeing, you have probably noticed it comes in several forms. Some people take capsules at home, others have subcutaneous injections, and some opt for an intravenous (IV) drip at a clinic. It can be confusing to work out how these compare, and whether one route is meaningfully different from another. This article walks through the main options in plain English so you can have a more informed conversation with a clinician.

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme found in every cell, involved in energy metabolism and cellular repair pathways. Interest in topping it up has grown, and NAD+ is now offered through several routes. If you would like a fuller primer on the molecule itself, our guide on What is NAD+? is a good place to start.

The main ways people take NAD+

Broadly, there are three routes you will come across in the UK: oral precursors, subcutaneous injections, and IV infusions. They differ in how the compound reaches your bloodstream and cells, how convenient they are, and how they are supervised.

  • Oral precursors — capsules or tablets, usually containing NMN (nicotinamide mononucleotide) or NR (nicotinamide riboside) rather than NAD+ itself. These are precursor molecules the body converts along the pathway toward NAD+.
  • Subcutaneous injection — a small injection into the fatty layer just under the skin, often self-administered at home after guidance, or given at a clinic.
  • IV infusion — NAD+ delivered directly into a vein through a drip, typically over a longer session in a clinical setting.

A key distinction runs through all of this: oral options are generally precursors that your body has to convert, whereas injections and IV are designed to deliver NAD+ more directly. That difference shapes much of the discussion below, though it is worth saying up front that head-to-head human evidence comparing the routes over the long term is limited.

Oral NMN and NR — how precursors work and bioavailability questions

When you take an oral supplement marketed around NAD+, you are almost always taking a precursor rather than NAD+ itself. The two most common are NMN and NR. Both sit on the salvage pathway, a series of steps the body uses to recycle building blocks into NAD+. In simple terms, you supply raw material and your cells do the conversion.

NMN vs NR — what is actually different?

NMN and NR are closely related; NR is one step "earlier" and is thought to be converted into NMN before continuing toward NAD+. Debate continues among researchers about how each is absorbed and transported into cells, and whether one offers any practical advantage over the other. At present there is no settled consensus, and much of the research is early or based on laboratory and animal models rather than large long-term human trials. It is fair to view the NMN vs NR question as unresolved rather than decided.

The bioavailability question

Anything swallowed has to survive the digestive tract and pass through the liver before reaching the wider circulation, a process known as first-pass metabolism. This can reduce how much of an active compound ultimately becomes available to the rest of the body. With oral NAD+ precursors, questions remain about how efficiently they are absorbed and how much they raise NAD+ levels in different tissues. Convenience is a clear draw of the oral route, but the trade-off is this uncertainty about bioavailability. A UK-registered clinician will advise based on your individual circumstances rather than on general claims.

Subcutaneous NAD+ injections — what they involve

Subcutaneous injections deliver NAD+ into the fatty tissue just beneath the skin, commonly in the abdomen or thigh, using a small needle. Because the compound does not pass through the gut and liver first, this route bypasses first-pass metabolism, which is one reason people consider it as an alternative to oral precursors.

In practice, subcutaneous injections are often provided as part of a supervised programme. After an initial assessment and demonstration, some people are able to self-administer at home following clear instructions, which many find more practical than attending a clinic for every dose. Others prefer to have each injection given by a professional. Technique, site rotation and safe sharps disposal all matter, and these are things a clinician or nurse will talk you through.

As with any injection, there can be local effects such as tenderness, redness or mild swelling at the site. If you are weighing up this route, our article on NAD+ injections: safety and side effects covers what to look out for in more detail. Any injectable used in the UK should be handled through appropriately regulated channels, and medicines are overseen by the MHRA; a GPhC-registered pharmacy is one such channel.

IV NAD+ infusions — how they differ and practical points

IV infusions place NAD+ directly into the bloodstream through a vein. Like subcutaneous injection, this avoids first-pass gut metabolism, but it differs in a few practical ways that are worth understanding.

The most notable is pace. IV NAD+ is characteristically given slowly, often over a session lasting a couple of hours or more. This is because rapid infusion is commonly associated with transient effects such as flushing, nausea, a feeling of chest tightness or restlessness. Slowing the drip rate is the usual way these are managed, and they typically ease when the pace is reduced. This is one reason an IV NAD+ drip in the UK is delivered in a supervised clinical setting rather than at home, so the rate can be adjusted and you can be monitored throughout.

Practical points to keep in mind

  • Time commitment — sessions are longer than an injection and require attending a clinic.
  • Supervision — a trained professional sets up the cannula, monitors you and adjusts the flow rate.
  • Comfort — because of the effects linked with fast infusion, the drip is deliberately unhurried.
  • Suitability — not everyone is a candidate; your medical history and any existing conditions or medicines will be reviewed first.

People sometimes assume IV must be superior simply because it is more involved, but the evidence does not clearly establish that any single route is better for general wellbeing. What the routes mainly differ in is directness of delivery, convenience and setting, rather than proven comparative outcomes.

How a clinician helps you choose, and monitoring

With three routes and genuine gaps in the comparative evidence, choosing sensibly is less about finding a universal answer and more about matching an option to you. This is where a UK-registered clinician plays a central role. They can take a full history, review your medicines and any conditions, discuss your goals and explain what is realistic, and flag anything that would make a particular route unsuitable.

Factors that often come into the conversation include how comfortable you are with needles or self-injecting, whether attending a clinic for infusions fits your life, your preference for convenience versus more direct delivery, and your individual health picture. There is no one-size-fits-all route, and a clinician will individualise the choice with you rather than apply a blanket recommendation.

Monitoring matters too. A responsible programme usually includes a baseline assessment, a review of how you are getting on, and a plan for what to do if you notice side effects. You should always be able to ask questions and change course. It is also worth remembering that NAD+ options for wellbeing are not a substitute for the fundamentals — sleep, nutrition, physical activity and managing existing conditions with your NHS GP where relevant.

If you would like to understand what the research does and does not show before deciding anything, our overview of NAD+ for energy and ageing sets out the current evidence in a balanced way. The overall picture is one of active, evolving research rather than settled conclusions, so approach any strong claims with healthy caution.

In short: oral NMN and NR are convenient precursors your body converts, with open questions about bioavailability; subcutaneous injections and IV infusions deliver NAD+ more directly by bypassing first-pass metabolism, with IV given slowly for comfort and under supervision. Which, if any, suits you is a personal decision best made with a UK-registered clinician who knows your circumstances.