NAD vs B12: which energy injection actually fits?

What each injection actually does

The first thing to understand is that NAD and B12 are fundamentally different molecules solving fundamentally different problems.

Vitamin B12 is a cobalamin that your body uses to make red blood cells, protect the coating on your nerves, and break down fats, carbohydrates, and proteins into energy your cells can actually use. If your B12 level is low because you don't eat enough meat and dairy, because your gut doesn't absorb it properly, or because you've had certain surgeries, your cells struggle to produce energy. You feel foggy, tired, weak. B12 injections bypass your digestive system entirely, delivering the vitamin straight into your bloodstream. If you're deficient, your body starts using it right away, and most clients notice improvement within 3 to 7 days as B12 reaches every system.

NAD (nicotinamide adenine dinucleotide) is something different. It's a coenzyme present in every cell, and it's central to the electron transport chain in your mitochondria. NAD+ helps convert nutrients into ATP, which is the actual fuel your cells burn. In theory, if your NAD+ levels are depleted, your cells produce less energy overall. An NAD injection is supposed to raise your NAD+ levels and help your mitochondria work more efficiently. But here's the catch: most of what we know about NAD comes from animal studies and cell research. In humans, clinical evidence for injectable NAD is very thin. Some people report feeling increased energy for several days to a few weeks after an injection. Others feel nothing. There are no studies confirming how long a single dose actually raises your NAD+ levels or exactly how much that translates to feeling better.

When B12 actually works

B12 injections are most effective when your tiredness is caused by B12 deficiency or poor B12 absorption. That might sound obvious, but it's crucial: if your blood B12 level is normal, a B12 injection won't make you less tired. If it's low, you'll likely feel significantly better.

I see this in clinic regularly. Someone comes in exhausted, their GP blood work showed low B12, they've been prescribed injections, and within a week they're noticeably brighter. The injection works because it's replacing something their body is actually short of.

B12 is also used in some specialist settings for conditions that genuinely benefit from it. A small pilot study of ME/CFS patients, for example, found that 34 out of 51 reported favourable response to B12 supplementation, with significant improvements in physical activity and fatigue levels. That's not a cure, but it's meaningful for a group with very limited options.

The key point: if your GP blood test showed normal B12, injections are unlikely to help. If it showed low B12, they often do.

What NAD might do, and what we don't know

NAD is marketed as a cellular repair and anti-ageing agent. The biological logic is sound: NAD+ is essential for mitochondrial function and for activating certain cellular repair pathways called sirtuins. In animals, raising NAD+ levels has shown some anti-ageing benefits. In humans taking oral NAD supplements, blood NAD levels do go up. But whether raising NAD via injection genuinely improves how you feel or function remains unclear.

In my practice, clients who choose NAD report varied outcomes. Some say they feel a bit more alert or have better stamina for a few weeks. Others notice nothing. A few report mild side effects like nausea, flushing, headache, or injection site soreness, though these are usually mild and fade within a few hours.

Importantly, NAD injections are not approved by the FDA or any other major regulator for any medical indication. That doesn't mean they're unsafe, but it does mean there's no governmental body that has rigorously tested them. You're essentially participating in an emerging treatment that might help and probably won't harm you, but whose benefit is mostly anecdotal.

Blood work first: why your GP test matters more than either injection

If you're tired, the most responsible first step is a blood test. Not an aesthetic injection. A proper GP workup.

UK guidelines recommend a core set of investigations when someone presents with unexplained tiredness: full blood count, ferritin, thyroid function, liver and kidney function, inflammation markers, and blood glucose. Those tests will identify whether you have anaemia, an underactive thyroid, iron deficiency, liver disease, or undiagnosed diabetes. Any of those will make you feel exhausted, and any of those will respond far more reliably to actual treatment than either NAD or B12 will.

NHS blood tests are free, though they can involve longer waiting times. Private testing is faster and can include additional markers like vitamin D, B12, magnesium, and HbA1c that aren't always in standard NHS panels. A practitioner like me can advise on private testing options, but the principle is the same: find out what's actually causing your tiredness before you start injecting anything.

Once blood work is done and your GP has ruled out serious causes, then the conversation shifts. If your B12 is low, B12 injections make sense. If your blood work is normal but you're still tired and you want to try supporting cellular energy, NAD is an option, though manage your expectations. If your GP suspects ME/CFS or another chronic condition, they may recommend specialist referral rather than aesthetic treatments.

Who chooses each one, in practice

In my clinic, I see different groups reach for each treatment.

B12 clients are often those whose GP has confirmed low B12 and who want a faster or more convenient route than oral supplements. Some have poor gut absorption and need injections to bypass their digestive system. Others simply prefer the ritual and measurable nature of an injection. They usually return with clear, repeatable results.

NAD clients tend to be those interested in longevity and cellular optimisation, who've done blood work and know they're not simply deficient in something basic. They're willing to try something newer and less certain because the logic appeals to them and they see it as supporting their overall vitality, not a quick fix for tiredness. Some combine NAD with other treatments focused on skin quality or cellular health.

A short safety note

Both B12 and NAD injections are low-risk when administered by a trained practitioner using sterile technique. The most common side effects are mild: injection site soreness, nausea, headache, flushing. These resolve within hours.

However, I want to be clear about what I see in the wider industry. Vitamin B12 injections have moved from clinical treatment into mainstream wellness, and many clinics offering them have minimal training. The legal framework in the UK allows non-medical practitioners to administer methylcobalamin (the form used in wellness shots) if properly trained and insured, but training standards vary wildly. If you choose B12, choose a clinic where the practitioner can demonstrate proper qualifications and insurance.

NAD injections sit in a greyer regulatory space. They're not FDA-approved, and the MHRA hasn't formally cleared them either. That means they're available, but the onus is on individual clinics to ensure they're sourcing safe products and administering them properly. Again, choose carefully and check credentials.

At Visage Aesthetics, I follow high standards on training, sourcing, and record-keeping because I believe aesthetics is a real clinical field that deserves to be taken seriously. Not every clinic does. That's partly why I'm writing this: to help you make an informed choice rather than just booking the thing that sounds good.

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