Eight nutrients carry authorised UK claims for reducing tiredness and fatigue: vitamins B2, B3, B6, B12, folate, vitamin C, magnesium and iron. Each feeds the machinery that makes energy inside your cells so they help if you're short of one, and little if you're not.
| Nutrient | Role in energy production | Authorised GB claim | Food sources | |||
| B1 (thiamine) | Converts carbohydrate into ATP | Normal energy-yielding metabolism | Pork, whole grains, legumes | |||
| B2 (riboflavin) |
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| B3 (niacin) | Raw material the body builds NAD from |
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Poultry, fish, peanuts | |||
| B5 (pantothenic acid) | Forms coenzyme A, the entry point to the Krebs cycle | Normal energy-yielding metabolism | Mushrooms, avocado, chicken | |||
| B6 (as P-5-P) |
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| B7 (biotin) |
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Normal energy-yielding metabolism | Eggs, nuts, sweet potato | |||
| B9 (folate) | Methylation cycle; red blood cell formation | Reduction of tiredness and fatigue | Leafy greens, lentils, liver | |||
| B12 (as methylcobalamin) |
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Energy-yielding metabolism and reduction of tiredness and fatigue |
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| Vitamin C |
Improves iron absorption; regenerates antioxidants |
Energy-yielding metabolism and reduction of tiredness and fatigue |
Peppers, citrus, blackcurrants |
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| Magnesium |
Binds ATP — ATP is only biologically active as Mg-ATP |
Energy-yielding metabolism and reduction of tiredness and fatigue |
Pumpkin seeds, spinach, dark chocolate |
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| Iron |
Carries oxygen; forms part of the electron transport chain |
Energy-yielding metabolism and reduction of tiredness and fatigue |
Red meat, liver, lentils |
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| Copper |
Loads iron onto its transport proteins |
Normal energy-yielding metabolism |
Shellfish, nuts, seeds |
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| Vitamin D |
Low levels associate with fatigue; mechanism unclear |
No authorised energy or fatigue claim |
Oily fish, egg yolk, sunlight |
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| CoQ10 |
Electron carrier in the final stage of ATP production |
No authorised claim |
Organ meats, oily fish |
Almost all of your usable energy is made in the mitochondria, the tiny power plants inside nearly every cell, with the hardest-working tissues like the heart, brain and muscles carrying thousands of them per cell. Their job is to take the food you eat and the oxygen you breathe and convert them, through a chain of chemical reactions, into a molecule called ATP. ATP is the actual currency of energy in the body: every heartbeat, thought and movement is paid for in it, and you make and spend your own body weight in it over the course of a day.
This matters because it reframes the whole question. When people say they want more energy, what they physically need is efficient ATP production. Almost every nutrient in this article earns its place not because it is stimulating, but because it is a cog in that machinery, a cofactor, a carrier or a raw material the mitochondria cannot run without. Optimise the machinery and the energy follows. Flog a tired system with caffeine and stimulants and you borrow energy you do not have, which is a different thing entirely.
It also means the most powerful lever of all is the health and the number of your mitochondria, and both are trainable. Regular movement, and exercise in particular, is the single strongest stimulus for building new mitochondria, which is a large part of why fitter people have more day-to-day energy to draw on. Giving the body real overnight fasting windows rather than grazing until bedtime, not habitually overeating, and protecting your sleep all help the mitochondria stay efficient and renew themselves. No capsule substitutes for any of this, which is exactly why I treat the nutrients below as support for a well-run system, not a shortcut around a neglected one.
Tiredness and fatigue are often used interchangeably, but they tell us very different things about the body. Tiredness is a normal, healthy response to effort: a long day, a hard training session or a short night. It has a clear cause, and it lifts with good sleep, rest and nourishment. Fatigue is different. It lingers even when you have slept well, it does not match how much you have done, and it can affect your focus, mood and motivation as much as your energy. From a nutrition and functional medicine perspective, persistent fatigue is a signal worth investigating rather than pushing through. Common drivers include low iron or ferritin, low vitamin B12 or vitamin D, unstable blood sugar, thyroid imbalances, chronic stress, poor gut health and low-grade inflammation, all of which can affect how efficiently our cells produce energy. That is why more caffeine or an early night rarely solves it. The aim is to find and address the root cause, ideally alongside your GP and appropriate blood tests.
Before any supplement, the honest clinical step is to ask why you are tired, because the answer is frequently not a deficiency. A systematic review of tiredness in primary care found that its causes are wide-ranging, spanning physical conditions such as anaemia and thyroid problems, mental health factors like stress and low mood, and lifestyle drivers, with no single cause dominating (10). In my experience the most common culprits are poor or broken sleep, unrelenting stress, blood sugar that swings through the day, an under-active thyroid, and low iron or B12. None of these is fixed by a generic energy supplement, and reaching for one while the real driver goes unaddressed is the first and most expensive mistake people make.
So, the groundwork comes first. If your sleep is poor, that is where the energy is leaking, and it is worth reading our full guide on how to sleep better at night before anything else. Stabilising blood sugar with balanced, protein-containing meals rather than caffeine and quick carbohydrates does more for most people's afternoons than any capsule. And a simple blood panel from your GP, covering ferritin, B12, thyroid function and vitamin D, will tell you far more than guesswork. With that foundation in place, the following nutrients are the ones with a genuine role in energy production.
If any group of nutrients deserves the title of energy vitamins, it is the B complex. The eight B vitamins are the essential cofactors that allow the mitochondria to extract energy from food; without them, the reactions that produce ATP simply stall. Thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5) and biotin (B7) all work directly inside the energy-producing pathways, while B6, folate (B9) and B12 support the wider metabolic and methylation processes that keep the whole system running (8). This is why genuine B vitamin deficiency shows up so reliably as fatigue, and why B12 in particular is one of the first things I check in anyone who is exhausted. I explain the best forms in a section below.
Second, because B vitamins are water-soluble and not stored in large amounts, they need to come in steadily through diet, from whole grains, eggs, leafy greens, legumes and quality animal proteins, with supplementation filling the gap where needs are high or intake is poor.
If B3 is the raw material, NAD is what it becomes, and it is arguably the single most important molecule in this entire conversation. NAD, made in the body from niacin, is the coenzyme that shuttles electrons through the mitochondria to generate ATP. Nothing about cellular energy production happens without it. It is also central to DNA repair and to the activity of the sirtuins, the enzymes involved in healthy ageing, so its reach extends well beyond feeling energetic (4).
Here is the part that makes it so relevant to tiredness, particularly past our thirties. NAD levels decline with age, and that decline is now understood to be a meaningful contributor to the drop in mitochondrial function and energy that so many people notice as the years pass (4). This is why supporting your body's own NAD production has become such a focus in the longevity field. The most effective strategies are partly nutritional, ensuring adequate niacin and the B vitamins NAD synthesis depends on, and partly about protecting NAD through the lifestyle basics that preserve mitochondrial health: regular movement, not overeating, good sleep and managing the chronic stress that drains it. Making and keeping your own NAD is a more sustainable goal than chasing it through any single product.
In the context of aging, research increasingly shows the decline in mitochondrial function and NAD levels is modifiable with movement, optimal fatty acid consumption, adequate vitamin D and a polyphenol-rich diet.
There is a deeper reason to care about all of this, and it is one of the more exciting developments in the field. The same decline in mitochondrial function and NAD that drains energy with age is now understood to be bound up with biological ageing itself, the rate at which your cells actually age, as opposed to the candles on the cake. And that rate turns out to be modifiable.
Coenzyme Q10 sits at the heart of the mitochondrial machinery, ferrying electrons along the final stretch of the chain that produces ATP and doubling as a potent antioxidant that protects the mitochondria from the wear of their own work. The body makes its own, but production falls with age, and it is depleted further by statin medications, which block part of the same pathway that manufactures it (1). This is one reason fatigue is such a common complaint among older adults and long-term statin users.
The evidence here is more direct than for most supplements. A 2022 systematic review and meta-analysis of thirteen randomised controlled trials, covering more than eleven hundred participants, concluded that coenzyme Q10 supplementation produced a significant reduction in fatigue compared with placebo, with higher doses and longer courses working better, and an excellent safety record (11). It is not a stimulant and will not produce an overnight transformation, but it is one of the more interesting and better-studied options in this area, particularly for anyone older or taking a statin.
Magnesium rarely gets mentioned in energy conversations, which is a genuine oversight, because the biochemistry could not be clearer. ATP does not actually work as a free molecule. It is biologically active only when bound to magnesium, as Mg-ATP, so magnesium is a non-negotiable partner in every single energy transaction your body makes (5). Add the fact that magnesium is also a cofactor in over three hundred enzyme systems, many of them metabolic, and you have a mineral that is quietly fundamental to feeling energised rather than depleted.
The problem is that magnesium is widely under-consumed on modern diets, and stress depletes it further, so a shortfall is common in exactly the tired, stretched people most likely to be looking for an energy fix. Correcting it will not make a well-supplied person buzz, but in someone genuinely low it can lift a layer of fatigue that no amount of caffeine was touching. I have written in detail on the best form of magnesium and why the bisglycinate form is so well tolerated, which applies just as much to daytime energy as to sleep.
Iron earns its place because the mitochondria cannot make energy without oxygen, and iron is what carries oxygen through the blood and also forms part of the electron transport chain itself. Low iron is one of the most common and most missed causes of persistent tiredness, especially in menstruating women, and crucially it causes fatigue well before it ever shows up as anaemia on a standard blood test (13). A randomised controlled trial in non-anaemic women with low ferritin and unexplained fatigue found that iron supplementation significantly reduced their tiredness compared with placebo, which tells you the deficiency was doing real damage long before the usual threshold for treatment.
This is why I always ask for a ferritin test, which measures stored iron, rather than relying on haemoglobin alone. But here is where I part company with the standard advice, and it matters: I do not reach for an iron supplement unless it is genuinely necessary. Iron does not work in isolation, and taking it alone, or in excess, can do more harm than good. Restoring healthy iron and ferritin levels depends on the wider mineral and vitamin picture, and copper in particular. Through the protein ceruloplasmin, copper is required to transport and load iron properly, so a copper shortfall can leave iron stranded and unused however much you take, while vitamin C meaningfully improves its absorption, and vitamin A, magnesium and vitamin D all play supporting roles (3 and 6). So, I favour correcting iron through food first, red meat, liver, lentils and dark leafy greens paired with vitamin C, while addressing the whole mineral balance, rather than defaulting to a standalone iron supplement. Iron is best supplemented only when a test shows it is genuinely needed, and ideally with professional guidance.
Vitamin D, which we've included in our Active State formula is worth including because deficiency is so widespread, particularly through the darker months at UK latitudes, and because low levels are consistently associated with fatigue and low mood. The evidence that correcting it helps is encouraging rather than emphatic: a double-blind, placebo-controlled trial found that a single high dose of vitamin D significantly improved self-perceived fatigue in otherwise healthy people with low levels (9). It is not an energiser in the way people imagine, but running short of it can quietly flatten how you feel, and it is one of the simplest things to test and correct. As I have noted elsewhere, vitamin D is best taken alongside its cofactors, magnesium and vitamin K2, rather than in isolation.
So far this has been about the raw materials of energy production, but a great deal of modern tiredness is driven not by deficiency at all but by relentless stress, and this is where adaptogens have a role. Adaptogens are a class of botanicals traditionally used to help the body cope with stress, and the thinking is that by buffering the cortisol-driven exhaustion that flattens so many people, they may help energy recover indirectly rather than by stimulating an already frazzled system.
Rhodiola rosea is the best evidenced of them for fatigue specifically. A systematic review of its use for physical and mental fatigue found consistent, if still preliminary, evidence that it improves both, particularly the mental fatigue and diminished performance that come with stress and burnout (7). We've included Rhodiola in our social state formula for stress induced fatigue. Cordyceps, a medicinal mushroom, has traditionally been used to support stamina and physical endurance. The appeal of adaptogens is that, unlike caffeine, they are not thought to whip the system but to help it cope, which is why they are often chosen for the tired-but-wired state that stimulants only make worse. As ever, they are most useful matched to the person, and most relevant where stress is genuinely the driver of the tiredness.
We favour methylated forms of Folate and B12 i.e. methylcobalamin over cyanocobalamin and methylfolate over folic acid. A significant proportion of people carry common gene variants, or SNPs, that change how efficiently they process these nutrients. Variants in the MTHFR gene, for example, reduce the body's ability to convert folic acid into the active folate the methylation cycle actually uses, while a slow version of the COMT gene changes how quickly methyl groups are cleared, which is why some people feel wired rather than settled on high doses of methylated B vitamins (12). I have written a full guide on what methylation is and why methylated vitamins matter if you want the detail.
When it comes to vitamin B6 we generally prefer P-5-P over pyridoxine hydrochloride (the cheaper form) as numerous enzymes and B2 are required to convert the hydrochloride form into it's active form P-5-P. Genetics may effect a persons ability to convert the hydrochloride form into P-5-P the active form.
We also recommend avoiding proprietary blends that don't declare individual amounts, and "energy" claims built on caffeine or sugar rather than nutrients.
How long until you actually feel a difference? That depends less on the supplement than on whether you were deficient to begin with. Correcting a shortfall is gradual; energy rarely returns overnight.
Vitamin B12: When low B12 contributes to fatigue, some people feel better within two to four weeks. Blood-count recovery is typically checked around eight weeks, although other symptoms can take longer.
Iron: Often the slowest to replenish. Haemoglobin may improve within weeks, but rebuilding ferritin (your iron stores) can take eight to twelve weeks, with full repletion often requiring three to six months. Don't abandon iron at four weeks assuming it has failed.
Vitamin D: Blood levels may rise meaningfully over eight to twelve weeks of appropriate replacement, sometimes longer in winter when sunlight contributes less.
Magnesium: Symptoms related to a shortfall may ease within days to a couple of weeks, although restoring intracellular stores takes longer.
CoQ10: The meta-analysis cited earlier (11) found greater fatigue improvements with longer courses. Think weeks to months, not days.
Adaptogens: Rhodiola trials have reported improvements over one to four weeks, though results vary by extract and person.
Here is what we most want you to take away, because it is where almost everyone goes wrong. The best supplements for energy are not the ones everyone is talking about; they are the ones that address what is actually depleted or dysfunctional in you. A person exhausted from low iron will feel nothing from CoQ10, and someone whose fatigue is driven by poor sleep and high stress will not be rescued by a B complex. How you respond is shaped by your own genetics, your epigenetics and your individual biochemistry, and the supplement that transforms one person's energy can do nothing at all for the next.
This is precisely why I am wary of the trend-led approach, where people take whatever is having its moment online and are then disappointed when it does nothing. The value of testing, and of working with a practitioner, is that it turns guesswork into a targeted plan matched to your biology. Food comes first, always, and the nutrients above work best as a considered addition to a nutrient-dense diet, not a substitute for one, and not a scattergun of everything at once.
Finally, and importantly, some tiredness is a signal that deserves proper medical attention rather than a supplement. If your fatigue is severe, persistent for weeks despite reasonable sleep, or accompanied by other symptoms such as unexplained weight change, breathlessness, low mood, or a general sense that something is not right, please see your GP. The causes of persistent tiredness range from iron deficiency and thyroid disorders to a number of conditions that need diagnosing and treating properly, and a straightforward set of blood tests is often all it takes to find the answer (10). Nutritional support is a genuine and valuable tool, but it works best on a foundation of knowing what you are actually dealing with.
Energy is made, not swallowed. It comes from your mitochondria, and the best vitamins for energy are the ones that keep that machinery supplied and working: the B vitamins and the NAD they build, coenzyme Q10, magnesium, and, where a test shows a shortfall, iron and vitamin D. But the single most important step is not a supplement at all. It is ruling out the real reasons you are tired, then matching support to your own biology rather than to the trend of the moment. Do that, and the nutrients above become genuinely useful. Skip it, and you are simply spending money on someone else's answer.
B12 is the one I check first, because deficiency is common, it causes profound fatigue, and it is easily missed. But "best" depends entirely on what you're short of — B12 will do nothing for someone whose tiredness is driven by low ferritin or poor sleep.
Most often B12, iron, vitamin D or folate. A blood panel covering ferritin, B12, folate, thyroid function and vitamin D will identify which or rule all four out, which is just as useful.
It depends on what you were short of. Correcting a B12 deficiency can lift fatigue within two to four weeks. Iron takes longer typically eight to twelve weeks to rebuild ferritin stores. If you weren't deficient, you should not expect to feel anything at all.
Usually because the vitamins weren't the problem. Poor sleep, chronic stress, blood sugar swings and an under-active thyroid all cause fatigue that no supplement will touch. It is also possible you are taking a form your body processes poorly folic acid rather than methylfolate, for instance.
For iron, yes I would not supplement it without one. For B vitamins, vitamin C and magnesium, which are water-soluble or well tolerated, testing is helpful but not essential. For persistent fatigue of any kind, a blood panel should come before a supplement, not after.
Start by testing rather than taking. Where a shortfall is confirmed, the B vitamins, magnesium, iron and vitamin C all have authorised roles in reducing tiredness. Where stress is the driver rather than deficiency, adaptogens such as rhodiola have better evidence than stimulants.
This article is intended for informational purposes only and does not constitute medical advice. The content reflects the author's professional knowledge and the current state of published research, but should not be used as a substitute for consultation with a qualified healthcare professional. Persistent or severe fatigue should always be assessed by your GP. If you have a health condition or take medication, please seek guidance before introducing any new supplement.
BA (Hons) BSc MSc
Neuroscientist & Cognitive Health Specialist
Inder guides our work in cognitive performance, neuroprotection, and stress physiology — ensuring our formulas support the brain with precision and scientific depth.
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