The Ultimate Guide to NAD Therapy: Combat Fatigue and Low Energy

I want to tell you about the moment longevity medicine stopped being a concept and became something I could not ignore clinically.

I was in cardiac nursing when I first encountered what NAD+ depletion actually looks like from the inside. Not a blood result on a panel. The actual physical picture: a failing heart struggling to extract energy from fuel that is right there, available, circulating. The mitochondria stalled. The cellular machinery running on fumes. My cardiac training drilled into me that energy failure at the cellular level is not an abstract phenomenon. It has consequences you can measure, see, and feel. Eventually, consequences you cannot reverse.

That understanding never left me when I moved into longevity medicine and aesthetics. If anything, it sharpened. Because the same biology I watched unfold in the catheterisation lab at KIMS Hospital shows up, in slower, quieter form, in almost every patient who walks into my clinic tired, foggy, and wondering why they are not recovering the way they used to.

The molecule at the centre of that picture is NAD+. But to understand why it matters, we need to start somewhere bigger.

What longevity medicine actually is

Most people arrive at longevity medicine through a very practical question. Not a philosophical one. Something like: why does my skin look so different from how I feel inside? Why am I recovering more slowly? Why does everything feel harder to maintain than it did a decade ago?

These feel like aesthetic concerns. They are not. They are biological ones.

Longevity medicine is the clinical science of slowing biological ageing, extending healthspan, and preserving vitality across the decades. It is not biohacking. It is not six-figure protocols for wealthy early adopters. It is an evidence-based clinical framework, applied preventively rather than reactively, rooted in established biochemistry and decades of peer-reviewed research.

The distinction I find most useful is the one between lifespan and healthspan. Lifespan is how long you live. Healthspan is how long you live well, with sufficient energy, cognitive clarity, physical capacity, and resilience to do the things that make life worth living. These two numbers are not the same. In the UK, they are diverging.

According to the Health Foundation's 2025 analysis, the gap in healthy life expectancy between the most and least deprived deciles in England is now 19.4 years for men and 20.3 years for women. In Richmond, a man's healthy life expectancy reaches 69.3 years. In Blackpool, it falls to 50.9. The biology of ageing does not just vary by age. It varies by postcode.

Longevity medicine is the clinical discipline that asks: why does this happen, and what can we actually do about it?

The biology of healthspan inequality

Here's what the data shows, and why it matters to clinical practice.

The healthy life expectancy gap is not primarily genetic. Genetics accounts for roughly 20 to 30% of how we age. The rest comes from modifiable biological factors: chronic inflammation, hormonal decline, mitochondrial function, sleep quality, metabolic health, and the sustained physiological effects of psychological stress.

These factors do not affect everyone equally. Chronic financial stress elevates cortisol in measurable, consistent ways. Ultra-processed food is cheaper and far more accessible in deprived areas. Sleep is harder to protect when economic pressure is constant. The biological markers of accelerated ageing, elevated high-sensitivity CRP, lower NAD+ levels, disrupted cortisol rhythms, impaired sleep architecture, cluster in the same populations that experience the worst health outcomes.

I say this not to make a political point but a scientific one: longevity medicine is not a luxury for the wealthy. The biology it addresses is the same biology driving a nineteen-year gap in healthy life expectancy across England. The framing of healthy ageing as inherently elite is not just commercially irritating. It is scientifically dishonest.

The interventions that most reliably extend healthspan are not, at their foundation, expensive. Quality sleep. Zone 2 cardiovascular exercise. A diet low in ultra-processed food. Stress regulation. SPF. Resistance training. These are the foundations and they are accessible to most people. Clinical interventions like blood panels, IV therapies, hormonal optimisation, and NAD+ supplementation extend and accelerate what the foundations make possible. They do not replace them. I make that point to every patient I see.

NAD+ and why it matters

NAD+ is nicotinamide adenine dinucleotide. It is not simply an energy molecule, though energy is where most people start. It governs DNA repair, cellular senescence, mitochondrial function, and the sirtuins: a family of proteins that function as the body's longevity regulators. Think of them as the maintenance crew that keeps your cellular machinery running cleanly. Without enough NAD+, the crew cannot work.

At the most fundamental level, NAD+ sits at the centre of how your mitochondria convert nutrients into ATP, the energy currency every cell in your body runs on. NAD+ acts as a co-factor and electron carrier in that process. When levels fall, the conversion slows. Cells become surrounded by fuel they cannot use. They starve in the presence of plenty.

That image is not metaphor. It is what I watched happening in the heart, in slow motion, during my years in cardiology. Mitochondrial decline is not a cosmetic concern. It is systemic. It shows up everywhere, eventually.

Research published in PMC confirms that sirtuins act as NAD+-dependent regulators of metabolism, cell survival, and circadian rhythm. When NAD+ falls, sirtuin activity goes with it. The cellular maintenance programme goes quiet. Meanwhile, your DNA is sustaining thousands of small errors and breaks every single day. PARP enzymes are responsible for finding and fixing them. Research published in PubMed demonstrates that as NAD+ falls, PARP activity becomes substrate-limited. DNA damage accumulates. Cellular senescence accelerates. Tissues begin ageing faster biologically than they are ageing chronologically.

Here is a summary of where this plays out clinically:

NAD+ role	Mechanism	What declines when NAD+ falls
Cellular energy production	Electron carrier in mitochondrial oxidative phosphorylation	ATP output; persistent fatigue despite adequate rest
DNA repair	Substrate for PARP enzymes	Accumulation of DNA damage; accelerated biological ageing
Longevity regulation	Sirtuin activation	Metabolic regulation, inflammation control, circadian rhythm
Inflammatory modulation	Cytokine pathway regulation	Increased baseline inflammation; slower tissue recovery
Cognitive function	Neuronal energy supply	Brain fog; word retrieval difficulties; processing speed

Why NAD+ declines, and why it is hard to reverse

The decline is not a single mechanism. Several converging factors make it progressive and, by the time it becomes symptomatic, genuinely hard to reverse through lifestyle alone.

CD38 is an enzyme that becomes increasingly active with age. It consumes NAD+, breaking the molecule down faster than the body synthesises it. Chronic inflammation, UV exposure, poor sleep, and cumulative DNA damage all increase PARP activation, which burns through NAD+ reserves faster than baseline decline alone would predict. By around sixty, most people have roughly half the NAD+ of a healthy twenty-year-old.

The symptoms overlap considerably with what most people simply accept as middle age, which is precisely why depletion goes unidentified for years. Fatigue that does not respond to rest. Cognitive dulling. A recovery time that has quietly extended. Skin that is not responding to regenerative treatments the way it should, because collagen synthesis and fibroblast activity are downstream of cellular energy availability.

That last point is one I cannot emphasise enough. If I am offering a patient microneedling, polynucleotides, or exosomes and the results are underwhelming, I do not immediately increase the treatment intensity. I ask what the cellular environment looks like. Because biostimulation without the cellular energy to respond to it is like planting seeds in exhausted soil.

IV NAD+ therapy versus NMN supplements

This is where the practical distinction matters most, because it determines which approach is appropriate for each patient's situation.

NMN (nicotinamide mononucleotide) is the most direct precursor to NAD+. The body converts it via the salvage pathway without needing to synthesise the molecule from scratch. Scientists including David Sinclair at Harvard have described NMN research as a genuine breakthrough in our understanding of cellular ageing, and the evidence for NMN raising NAD+ levels is substantial and growing.

The challenge is bioavailability. Standard NMN capsules dissolve in the stomach. A significant fraction is degraded before reaching the bloodstream at meaningful concentrations. At Juvenology, we stock HINNAO NMN specifically because its sublingual liposomal delivery bypasses the digestive tract entirely, absorbing directly through the oral mucosa. For maintenance and long-term prevention, this is the most accessible and practical route.

IV NAD+ therapy is a different proposition altogether. Pharmaceutical-grade NAD+ delivered directly into the bloodstream means 100% bioavailability, immediate systemic distribution, and precise dose control. No digestive process. No conversion step. No guessing at absorption. The coenzyme is available to cells immediately.

Feature	HINNAO NMN (sublingual liposomal)	IV NAD+ therapy
Delivery	Sublingual, bypasses digestion	Direct intravenous infusion
Bioavailability	High (significantly better than standard capsules)	100%
Speed of effect	Hours to days for measurable cellular impact	Immediate systemic effect
Best suited for	Maintenance, prevention, ongoing support	Therapeutic restoration for significant depletion
Onset of noticeable benefit	Days to weeks	Often within 24 to 48 hours
Practical use	Daily at home	Clinic-based, 2 to 4 hours per session

For patients with significant depletion and clear clinical symptoms, IV is the therapeutic intervention. NMN is the maintenance strategy. Many patients use both: an IV course to restore levels, followed by daily sublingual NMN to sustain them. That combination makes clinical sense, and the results reflect it.

Testosterone and why it belongs in this conversation

NAD+ is not the only molecule whose decline shapes how we age. Testosterone is another, and its relationship to longevity medicine is one that most patients, and many clinicians, underestimate.

Both sexes produce testosterone throughout life, in very different quantities. Dermal fibroblasts are androgen-sensitive, meaning testosterone directly influences the cells responsible for producing collagen and maintaining dermal density. As testosterone declines from the mid-thirties onwards, collagen synthesis slows, muscle mass reduces, and the anabolic environment that supports tissue repair and regeneration deteriorates.

There is a wound healing paradox here that I find genuinely fascinating from an anatomical perspective. Male skin turns over cells more quickly than female skin at equivalent ages. You might expect faster healing as a result. The evidence shows the opposite: older men heal cutaneous wounds more slowly, and serum testosterone levels correlate negatively with healing rate. The mechanism is DHT, the more potent testosterone metabolite, which suppresses the inflammatory resolution phase that allows tissue repair to complete. If the hormonal environment is significantly depleted, the cells receiving biostimulation from any regenerative treatment lack the metabolic resources to respond fully. This is clinically relevant for anyone whose aesthetic results are falling short of what the treatment should produce.

For women, the perimenopause picture is equally significant. As oestrogen falls, the relative effect of testosterone on sebaceous glands and hair follicles shifts. Androgenetic alopecia in women presents as diffuse thinning at the crown and temples, driven by the same DHT-mediated follicular miniaturisation seen in men, but without the oestrogen counterbalance that previously modulated it.

The SHBG point matters here too. A standard blood test showing technically normal total testosterone can mask significant functional deficiency if SHBG (sex hormone binding globulin) is elevated, binding most of the available hormone away from tissue. Free testosterone, the fraction actually available to cells, is what matters clinically. This is why the Advanced Blood Panel at Juvenology includes free testosterone, SHBG, and DHEA-S, interpreted in the context of symptoms and stage of life rather than against a generic reference range that may not reflect your biology at all.

When a patient arrives whose regenerative treatments are not producing the results I would expect, hormonal status is one of the first things I want to understand. The biology is always telling you something. The skill is knowing the right questions to ask.

What longevity medicine looks like at Juvenology

Longevity medicine here is not a package and it is not a single treatment. It is a clinical framework applied individually, starting with understanding what is actually happening in your biology before making any recommendations at all.

The Advanced Blood Panel provides the foundation. It covers hormonal markers (oestradiol, free and total testosterone, DHEA-S, SHBG, FSH, LH, progesterone), thyroid function (TSH, Free T3, Free T4), metabolic markers (HbA1c, fasting glucose, full lipid profile), inflammatory load (high-sensitivity CRP), relevant metabolic markers informing cellular energy and NAD+ pathway status, and nutritional markers including vitamin D, B12, ferritin, folate, and zinc.

From that picture, the protocol is built. IV NAD+ therapy for patients with significant cellular energy deficit. HINNAO NMN as ongoing maintenance. Hormonal optimisation where indicated. Red light therapy for mitochondrial support and inflammaging reduction. Regenerative aesthetics for the dermal consequences of what the blood panel has revealed systemically. The goal is never to treat a list of separate concerns. It is to restore the biological environment in which every treatment, every cell, and every system in the body can work more effectively.

My postgraduate training in longevity medicine at the Geneva College of Longevity Science, alongside my qualification in hormonal health from the Marion Gluck Academy, fundamentally shapes how I approach this work. Not as a collection of interventions. As a clinical system grounded in the same respect for biology I developed in twenty-five years of nursing.

In cardiology, I learned that cellular energy failure has consequences you cannot see until they are serious. In longevity medicine, I have learned that the same biology, addressed early and addressed properly, offers something cardiology rarely could: the chance to intervene before the threshold is crossed.

Frequently asked questions

How do I know if my NAD+ levels are low?

There is no standard clinical test for NAD+ levels available in routine UK practice. The clinical picture, persistent fatigue, poor recovery, cognitive dulling, and regenerative treatments not producing expected results, combined with relevant blood markers, guides the decision. The Advanced Blood Panel identifies the metabolic and hormonal variables most closely connected to NAD+ pathway function.

Is IV NAD+ therapy safe?

NAD+ is a molecule your body produces and uses constantly. Replenishing it intravenously has a strong safety profile in the published literature. The most common effects during infusion are warmth, flushing, and mild chest sensation, all transient and rate-dependent. Every infusion at Juvenology is conducted with vital signs monitored throughout and a full medical history taken before any treatment is agreed.

Can NMN supplements replace IV NAD+ therapy?

They serve different purposes rather than competing with each other. NMN raises NAD+ via the salvage pathway and is appropriate for maintenance and prevention. IV NAD+ delivers the coenzyme directly into circulation with immediate bioavailability for therapeutic restoration. For significant depletion or specific clinical goals, IV provides a therapeutic dose that oral precursors cannot match. The most effective approach for many patients is an IV course to restore levels, followed by sublingual NMN to sustain them.

Is longevity medicine only for older patients?

No. The most effective time to intervene is before biological thresholds are crossed. Patients in their thirties and forties benefit substantially from the preventive and maintenance dimensions of this work. The biology of ageing is always moving. Working with it before it moves significantly is considerably more effective than addressing the consequences later.

Does testosterone really affect skin ageing?

Yes, through specific and measurable biological mechanisms. Dermal fibroblasts are androgen-sensitive. Testosterone decline reduces collagen synthesis, dermal density, and the anabolic environment that supports tissue repair. For both men and women, addressing hormonal status alongside aesthetic treatment consistently produces better and longer-lasting results than treating the surface while the underlying biology works against it.

Book a longevity medicine consultation at Juvenology

We see patients from across Kent including Maidstone, Tonbridge, Sevenoaks, Kings Hill, West Malling, Medway, and Chatham.

References

1. NAD+ and sirtuins in ageing and disease — PMC

2. The NAD+/PARP1/SIRT1 axis in ageing — PubMed

3. Sirtuins and NAD+ in metabolic and cardiovascular diseases — PMC

4. UK healthy life expectancy gap: 19.4 years male, 20.3 years female by deprivation — Health Foundation, 2025

5. ONS healthy life expectancy data 2022 to 2024 — ONS

6. Oestrogen and skin ageing: collagen loss post-menopause — PMC