Always Tired? It Might Not Be Sleep—Here’s the Real Culprit

It’s 2pm on a Wednesday. You slept eight hours last night. You’ve had your morning coffee, maybe two. You ate a decent lunch. And yet, here you are, staring at your computer screen like it’s written in a foreign language, fighting the overwhelming urge to put your head on your desk.

You’re not lazy. You’re not imagining it. And you’re definitely not alone. According to the NHS, feeling “tired all the time” is so common they’ve literally turned it into an acronym: TATT. It’s become one of the most frequent complaints GPs hear. In the United States, around 15% of women and 10% of men regularly report feeling exhausted, and here in the UK, the numbers tell a similar story.

You’ve probably tried everything. More sleep, less caffeine, better diet, exercise, cutting out alcohol, taking iron supplements. Some things help a bit, but that bone-deep exhaustion never really goes away. What if I told you the problem isn’t what you’re doing but what’s happening inside your cells that you can’t see?

The Cellular Battery Nobody Talks About

There’s a molecule in every single cell of your body called NAD+ (nicotinamide adenine dinucleotide). Think of it as your cells’ battery pack. It’s responsible for converting the food you eat into usable energy, repairing your DNA, and keeping your cellular machinery running smoothly.

Here’s the problem: your NAD+ levels decline dramatically as you age. Research published in the journal PLOS One found that NAD+ levels in men showed a clear downward trend with age, with the decline becoming particularly noticeable after puberty. The older you get, the less NAD+ you have.

Another comprehensive study tracking 1,518 participants found that NAD+ levels showed a notable decline in people aged 40-49, with men experiencing the steepest drops. By the time you reach 50, you might have 40-50% less NAD+ than you did in your twenties. That’s half your cellular energy capacity, gone.

Dr. Nessreen Rizvi, an internal medicine physician at Henry Ford Health, has noted that many patients who consistently get 7-9 hours of sleep still feel exhausted. In her clinical experience, whilst lifestyle factors like sleep quality, diet, and stress all matter, they don’t tell the whole story.

Why Your Cells Are Running on Empty

If NAD+ is like petrol for your cells, what happens when you’re running on fumes?

Your mitochondria (the tiny power stations inside each cell) can’t produce ATP efficiently. ATP is literally your body’s energy currency. Without enough NAD+ to facilitate the process, your mitochondria struggle to convert nutrients into the energy you need to function. It’s like having a perfectly good car but not enough fuel to get it moving.

The decline accelerates after 40, which explains why so many people in their late thirties and forties suddenly find themselves asking, “Why am I so tired all the time?” when nothing else in their life has really changed.

Think of it this way: if your cells were cars, NAD+ would be the fuel. Not just any fuel, but premium grade petrol that keeps everything running smoothly. You wouldn’t expect your car to perform the same on half a tank of low-grade fuel, would you?

The Signs Your NAD+ Might Be Depleted

Beyond constant fatigue, declining NAD+ levels can manifest in several ways:

Brain fog and poor concentration. You struggle to focus on tasks that used to be easy. Your memory feels fuzzy. Simple decisions feel overwhelming.

Slower recovery from exercise. You work out and feel wrecked for days afterward, rather than bouncing back quickly like you used to.

That persistent 3pm crash. No matter how much sleep you got, you hit a wall mid-afternoon that no amount of coffee can fix.

Looking and feeling older than your years. Your skin doesn’t recover as well, you wake up stiff, and you just feel… older.

Research shows that NAD+ plays a crucial role in DNA repair, cellular communication, and metabolic regulation. When levels drop, all of these processes slow down, which manifests as the exhaustion you’re feeling.

Why Lifestyle Changes Alone Aren’t Enough

Here’s the frustrating truth: while exercise, good sleep hygiene, and a healthy diet absolutely matter for energy levels, they can’t fully compensate for age-related NAD+ decline.

It’s like trying to fill a leaking bucket. As we age, certain enzymes in our bodies (particularly PARPs, which repair DNA damage, and CD38, involved in inflammation) consume NAD+ at an accelerating rate. Meanwhile, our ability to produce new NAD+ diminishes. The result? Your cellular energy deficit grows wider even when you’re doing everything “right.”

A major study in Nature Medicine tracking over 100,000 middle-aged individuals for three decades found that whilst nutrient-dense foods and healthy lifestyle patterns absolutely support healthy ageing, they couldn’t prevent the natural decline in cellular energy metabolism.

This is where NAD+ supplementation comes in.

The NAD+ Solution: What Actually Works

The most efficient way to boost NAD+ levels is through supplements containing precursors that your body can convert into NAD+. The most researched and effective precursor is NMN (nicotinamide mononucleotide).

Unlike taking NAD+ directly (which doesn’t absorb well), NMN is a smaller molecule that your body can efficiently convert into NAD+ once it’s inside your cells. Think of it as providing the raw materials your cells need to manufacture their own energy currency.

Clinical trials have demonstrated that NMN supplementation can increase blood NAD+ levels, with many people reporting improvements in energy, mental clarity, and overall vitality within 2-4 weeks of consistent daily use.

Finding Quality NAD+ Supplements That Don’t Break the Bank

Here’s where it gets tricky. The NAD+ supplement market has exploded, with products ranging from £30 to well over £100 for a month’s supply. Premium pricing doesn’t always mean premium quality, and many brands make wild claims about “reversing ageing” that aren’t supported by science.

Longevity Formulas, a UK-based brand founded by Mat Stuckey, takes a refreshingly different approach. After becoming frustrated with the disconnect between supplement marketing and actual science, Mat set out to create high-quality NAD+ precursor supplements that prioritise three things: quality, transparency, and honest pricing.

“I wanted to create a brand that was trustworthy and provided top quality longevity supplements without a premium price tag,” Mat explains. “Too many companies make outrageous claims whilst charging £60-80 for basic formulations. We focus on what the science actually supports.”

The brand publishes Certificates of Analysis for every batch on their website and manufactures all products in the UK under GMP regulations. Their Pure NMN supplement provides 500mg per capsule for £39.99 (a two-month supply), compared to £60-100+ charged by many competitors.

The range includes a straightforward Pure NMN formula, an NMN Complex with added resveratrol, TMG, and quercetin for those wanting a more comprehensive approach, and CoQ10 with Vitamin B1 for additional mitochondrial support. 

What to Expect When You Start Supplementing

It’s important to have realistic expectations. NAD+ supplementation isn’t a magic bullet that will transform you overnight. This is cellular-level support that builds up over time.

Most people notice subtle improvements within the first two weeks, perhaps slightly more energy in the afternoon, or waking up feeling a bit more refreshed. The more pronounced effects typically emerge after 3-4 weeks of consistent daily use.

Common improvements people report include:

• More sustained energy throughout the day, without the peaks and crashes
• Improved mental clarity and focus, particularly during cognitively demanding tasks
• Better recovery from exercise
• Feeling more resilient to stress
• Generally feeling more like “themselves” again

One user describes it as “feeling like my battery runs at 80% throughout the day instead of starting at 60% and declining.”

How to Use NAD+ Supplements Effectively

Dosage: Most research supports 250-500mg of NMN daily. Start with one capsule per day, taken with food.

Timing: Morning is often preferred as it aligns with your body’s natural circadian rhythms, though consistency matters more than specific timing.

Be Patient: Give it at least 3-4 weeks of daily use before evaluating results. This isn’t caffeine. It works by building up in your system over time.

Consider Combinations: Many people take NMN alongside CoQ10 for comprehensive mitochondrial support, as they work on related but different aspects of cellular energy production.

Important: Consult your doctor before starting any new supplement, particularly if you take medications or have existing health conditions.

The Bigger Picture: Supporting Your Cellular Health

NAD+ supplementation works best as part of a broader approach to cellular health. Continue prioritising:

• Quality sleep – Aim for 7-9 hours in a cool, dark room
• Regular movement – Even 30 minutes of walking daily supports mitochondrial health
• Nutrient-dense food – Focus on whole foods, plenty of vegetables, and adequate protein
• Stress management – Chronic stress depletes NAD+ faster
• Limiting alcohol – Alcohol consumption significantly drains NAD+ levels

But here’s the key: don’t wait until you’ve perfected everything else before addressing NAD+ decline. These approaches work synergistically. Supporting your cellular energy whilst improving your lifestyle gives you the energy to actually make those lifestyle changes stick.

Is This Really Worth It?

If you’ve been struggling with persistent fatigue despite doing “all the right things,” addressing NAD+ decline could be the missing piece you haven’t considered.

At under £20 per month for a quality supplement like those offered by Longevity Formulas, it’s significantly more affordable than many people assume, especially compared to endless GP appointments, trying countless other supplements, or resorting to IV treatments at £250-500 per session.

The research is clear: NAD+ levels do decline with age, and this decline does affect cellular energy production. What’s less clear is whether supplementation will work for every individual. However, given the safety profile of NMN supplements (generally well-tolerated with minimal side effects) and the growing body of research supporting their effectiveness, it’s worth considering, particularly if you’re over 35 and experiencing unexplained fatigue.

The Bottom Line

Feeling tired all the time isn’t something you have to accept as a normal part of ageing. Whilst lifestyle factors like sleep, diet, stress, and exercise all matter enormously, they don’t address the fundamental cellular energy decline that accelerates after 40.

NAD+ supplementation offers a science-backed approach to supporting your cells’ ability to produce energy. Combined with healthy lifestyle habits, it could be exactly what you need to finally feel like yourself again.

Your exhaustion isn’t in your head. It’s in your cells. And now you know there’s something you can actually do about it.

Explore NAD+ supplements: Longevity Formulas NAD+ Boosting Collection