Supplements for Tiredness and Fatigue: Which Nutrients Have Authorised Claims?

Why do so many people feel tired all the time?

Persistent tiredness is one of the most common complaints in UK primary care. According to the Royal College of General Practitioners, fatigue accounts for around 5-7% of all GP consultations, and surveys consistently show that roughly one in five adults reports feeling tired "most of the time."

Yet when people search for supplements for tiredness and fatigue, most advice jumps straight to product recommendations without asking the most important question first: why are you tired?

This article focuses specifically on tiredness and fatigue as symptoms of nutrient insufficiency — the nutrients that carry the EU-authorised claim "contributes to the reduction of tiredness and fatigue" — and what the clinical evidence shows for each one.

What causes tiredness and fatigue from a nutritional perspective?

Fatigue has many causes: poor sleep, chronic stress, underlying medical conditions, and overtraining, among others. But one of the most overlooked and correctable causes is inadequate intake of specific vitamins and minerals.

Several micronutrients are directly involved in cellular energy production — the process by which mitochondria convert food into ATP, the energy currency of every cell. When any of these nutrients falls below optimal levels, energy production becomes less efficient. The result is fatigue that no amount of caffeine or willpower resolves.

Under EU Regulation 432/2012, retained in UK law post-Brexit, the following nutrients carry the specific authorised claim "contributes to the reduction of tiredness and fatigue":

This is the complete list. No other vitamins, minerals, herbs, or compounds are legally permitted to make this claim in the UK.

How common are these nutrient deficiencies in the UK?

More common than most people realise. The National Diet and Nutrition Survey (NDNS) — the UK's most comprehensive dietary surveillance programme — reveals significant shortfalls across multiple nutrients linked to fatigue:

Iron: 49% of girls aged 11-18 and 25% of women aged 19-64 have intakes below the Lower Reference Nutrient Intake (LRNI)
Magnesium: up to 53% of adolescent girls and 19% of young adults aged 20-29 fall below the LRNI
Folate: more than half of 11-18 year-olds have serum folate concentrations below the threshold indicating possible deficiency
Vitamin D: nearly 1 in 5 adults (18%) are classified as deficient, rising to 31% during winter months

A secondary analysis of NDNS data by Derbyshire (2018) confirmed that UK females and younger adults are particularly vulnerable to multiple simultaneous micronutrient shortfalls — with a quarter of women falling below the LRNI for iron and potassium from food sources alone.

These are not marginal academic findings. They describe a substantial portion of the UK population walking around with nutrient levels too low to support normal energy metabolism.

How does iron deficiency cause tiredness?

Iron contributes to the reduction of tiredness and fatigue. It also contributes to normal oxygen transport in the body and normal energy-yielding metabolism — all authorised EU health claims.

The mechanism is straightforward. Iron is essential for haemoglobin, which carries oxygen from your lungs to every cell. It is also a critical component of mitochondrial enzymes involved in ATP production. When iron stores are depleted, oxygen delivery and cellular energy production are both impaired.

You do not need to be anaemic to experience iron-related fatigue

This is a point that deserves emphasis. Many GPs only test haemoglobin levels, but fatigue from low iron stores (measured by serum ferritin) can occur long before haemoglobin drops to anaemic thresholds.

Verdon et al. (2003) demonstrated this in a landmark double-blind, placebo-controlled trial of 144 non-anaemic women with unexplained fatigue. Those receiving 80mg of elemental iron daily showed a 29% reduction in fatigue scores compared to 13% in the placebo group, with the strongest benefit in women with ferritin levels below 50 mcg/L.

This finding was replicated by Vaucher et al. (2012) in a larger trial of 198 non-anaemic menstruating women with ferritin below 50 mcg/L. Iron supplementation for 12 weeks decreased fatigue by almost 50% from baseline — a significant 19% improvement compared to placebo.

The form of iron matters considerably for both absorption and tolerability. For a detailed comparison, see our guide to iron supplements: forms, absorption and how to choose.

Can B vitamins reduce tiredness and fatigue?

Six B vitamins carry the authorised claim "contributes to the reduction of tiredness and fatigue": B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6, B9 (folate) and B12. All eight B vitamins also carry the claim "contributes to normal energy-yielding metabolism."

This is not a coincidence. B vitamins function as coenzymes in the interconnected metabolic pathways that convert food into cellular energy:

B2 and B3 are components of FAD and NAD+, the electron carriers that drive the electron transport chain
B5 is a component of coenzyme A, required for fatty acid oxidation and the citric acid cycle
B6 is a coenzyme in amino acid metabolism and neurotransmitter synthesis
B9 (folate) is required for DNA synthesis and the methylation cycle
B12 is required for methylmalonyl-CoA mutase (mitochondrial energy) and methionine synthase (methylation)

As Kennedy (2016) argued in a comprehensive review, research has historically focused narrowly on B12, B9 and B6 through the lens of homocysteine metabolism, while the other B vitamins have received far less attention. In reality, all eight function synergistically — a deficiency in any single B vitamin can create a metabolic bottleneck that limits energy production.

Why B12 alone may not resolve fatigue

Vitamin B12 is the most commonly supplemented B vitamin for tiredness. But B12 works in tandem with folate and B6 in the methylation cycle. If your folate or B6 status is also suboptimal — which NDNS data suggests is common — supplementing B12 alone may not address the underlying issue.

Tardy et al. (2020) reviewed the biochemical and clinical evidence for vitamins and minerals in energy, fatigue and cognition, concluding that "even marginal deficiency in one or more of these micronutrients may lead to suboptimal metabolism and increased fatigue."

This is why a complete B-vitamin profile matters more than megadosing a single B vitamin. For a deeper comparison of B12 forms, see methylcobalamin vs cyanocobalamin.

Does magnesium help with tiredness?

Magnesium contributes to the reduction of tiredness and fatigue — an authorised EU health claim. It also contributes to normal energy-yielding metabolism, normal functioning of the nervous system, and normal psychological function.

Magnesium is a cofactor in over 300 enzymatic reactions, including ATP synthesis. Every molecule of ATP — the fundamental energy currency of every cell — must be bound to a magnesium ion to be biologically active. When magnesium is insufficient, energy production is directly impaired at the most fundamental level.

Cox et al. (1991) conducted a randomised, double-blind, placebo-controlled trial in 32 patients with chronic fatigue syndrome. The magnesium group showed significantly improved energy levels, better emotional state and less pain compared to placebo, alongside measurably higher red blood cell magnesium concentrations.

The NDNS consistently shows that a significant proportion of UK adults — particularly young women and adolescents — fall below recommended magnesium intakes. Factors that further deplete magnesium include chronic stress, alcohol consumption, and diets low in green leafy vegetables, nuts, seeds and wholegrains.

If your tiredness overlaps with poor sleep quality, magnesium may be doubly relevant. See our guide to magnesium for sleep for the clinical evidence.

What role does vitamin C play in reducing tiredness?

Vitamin C contributes to the reduction of tiredness and fatigue — an authorised EU health claim. It also contributes to normal energy-yielding metabolism and the protection of cells from oxidative stress.

Vitamin C's role in fatigue is multifaceted. It is required for the biosynthesis of carnitine, which transports long-chain fatty acids into the mitochondria for energy production. It also contributes to iron absorption — meaning that inadequate vitamin C can indirectly worsen iron-related fatigue.

Suh et al. (2012) conducted a double-blind, randomised controlled trial in 141 healthy office workers and found that vitamin C administration significantly reduced fatigue scores at both two hours and one day after intervention, with the effect being most pronounced in those with lower baseline vitamin C levels.

Sim et al. (2022) found that in healthy young adults with inadequate serum vitamin C concentrations (below 50 mcmol/L), supplementation with 500mg twice daily for four weeks significantly increased attention and work absorption, with a distinct tendency of improvement on fatigue compared to placebo.

These findings underline a consistent pattern: vitamin C supplementation is most effective for fatigue reduction in individuals whose baseline status is suboptimal. If your diet is already rich in fresh fruits and vegetables, additional vitamin C may provide less benefit.

Can vitamin D deficiency cause fatigue?

Vitamin D does not currently carry the authorised claim for "reduction of tiredness and fatigue." Its authorised claims relate to normal function of the immune system, maintenance of normal bones and teeth, and normal muscle function. We are transparent about this distinction.

However, the clinical evidence linking vitamin D deficiency to fatigue is growing substantially.

Nowak et al. (2016) conducted the first double-blind, placebo-controlled trial specifically examining vitamin D3 and fatigue in otherwise healthy individuals with low vitamin D status. Among 120 participants with serum 25(OH)D below 20 mcg/L, the vitamin D group showed a significantly greater reduction in fatigue scores compared to placebo (P = 0.01), with 72% reporting fatigue improvement versus 50% in the placebo group.

The EViDiF study (Roy et al., 2014) found that 77.2% of patients presenting in primary care with fatigue had low vitamin D levels, and that normalisation of vitamin D through supplementation significantly improved fatigue severity across all subscale categories.

With nearly 1 in 5 UK adults classified as vitamin D deficient — rising to 31% in winter — vitamin D status is worth checking if you are experiencing persistent tiredness, particularly between October and March.

For a comparison of supplement forms, see our guide to vitamin D supplements: D3 vs D2.

Which nutrients carry the "reduction of tiredness and fatigue" claim?

Nutrient	EU-authorised fatigue claim	Key role in energy metabolism	Forms to look for
Iron	Contributes to the reduction of tiredness and fatigue	Oxygen transport via haemoglobin; mitochondrial electron transport	Ferrous gluconate, ferrous fumarate
Vitamin B12	Contributes to the reduction of tiredness and fatigue	Methylation cycle; mitochondrial energy via methylmalonyl-CoA mutase	Methylcobalamin, adenosylcobalamin
Vitamin B6	Contributes to the reduction of tiredness and fatigue	Amino acid metabolism; neurotransmitter synthesis	Pyridoxal-5-phosphate (P5P)
Folate (B9)	Contributes to the reduction of tiredness and fatigue	DNA synthesis; methylation cycle	5-methyltetrahydrofolate (5-MTHF)
Vitamin B2 (riboflavin)	Contributes to the reduction of tiredness and fatigue	Component of FAD; electron transport chain	Riboflavin, riboflavin-5-phosphate
Vitamin B3 (niacin)	Contributes to the reduction of tiredness and fatigue	Component of NAD+; electron transport chain	Nicotinamide
Vitamin B5 (pantothenic acid)	Contributes to the reduction of tiredness and fatigue	Component of coenzyme A; citric acid cycle	Calcium pantothenate
Vitamin C	Contributes to the reduction of tiredness and fatigue	Carnitine biosynthesis; iron absorption; antioxidant defence	Ascorbic acid, calcium ascorbate
Magnesium	Contributes to the reduction of tiredness and fatigue	ATP activation; 300+ enzymatic reactions	Magnesium citrate, magnesium bisglycinate

How does PARTICULAR address tiredness and fatigue?

The fundamental problem with generic "anti-fatigue" supplements is that they assume everyone's tiredness has the same cause. It does not.

If your fatigue stems from low iron stores, no amount of B12 or magnesium will resolve it. If your tiredness is driven by inadequate magnesium alongside poor sleep, a standalone B-complex misses the point. If multiple marginal deficiencies are present simultaneously — which the NDNS data suggests is common in UK adults — a single-ingredient supplement addresses only one piece of a larger puzzle.

PARTICULAR's questionnaire assesses your diet, lifestyle, life stage, sleep quality and specific health concerns to identify which nutrients are most likely relevant for you. Your personalised formula then delivers those nutrients as microgranules — each ingredient individually coated for optimal stability and absorption — in one daily scoop.

Rather than guessing with a generic multivitamin or stacking individual supplements, this approach targets the actual nutritional gaps most likely contributing to your tiredness.

Key takeaways

Nine specific nutrients carry the EU-authorised claim "contributes to the reduction of tiredness and fatigue" — iron, vitamin B12, B6, folate, riboflavin, niacin, pantothenic acid, vitamin C and magnesium
Iron deficiency is the most common nutritional cause of fatigue in the UK, and clinical trials show that supplementation reduces tiredness even in non-anaemic women with low ferritin
B vitamins work as an interconnected complex — supplementing B12 alone may not help if folate or B6 are also insufficient
Magnesium is required for ATP activation and is widely under-consumed in the UK, with up to 53% of adolescent girls falling below the LRNI
Vitamin C contributes to the reduction of tiredness and fatigue, with clinical evidence showing the greatest benefit in those with suboptimal baseline status
Vitamin D does not carry the fatigue claim, but clinical trials show that correcting deficiency significantly improves self-reported fatigue
The cause of your tiredness determines which nutrient will help — a personalised approach identifies and addresses the specific gaps most relevant to you

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