Quick answer: the vitamins with EU-authorised claims for reduction of tiredness and fatigue are vitamin B12, folate (B9), vitamin B6, riboflavin (B2), niacin (B3), pantothenic acid (B5), and vitamin C. Iron is not a vitamin but is the most common single cause of fatigue in UK adults — particularly premenopausal women. Vitamin D does not carry an EU-authorised fatigue claim but is linked to musculoskeletal tiredness when severely deficient.
Why "energy vitamins" is a misleading category
No vitamin provides energy directly. Vitamins do not contain calories or ATP. What the B vitamins do is act as cofactors in the metabolic pathways that convert food (carbohydrates, fats, protein) into ATP — the molecule cells actually use for energy. Without adequate B vitamins, these conversions are less efficient. This is why the EU-authorised claim is specifically worded as "contributes to normal energy-yielding metabolism" and "reduction of tiredness and fatigue" — not "gives you energy."
The distinction matters practically: if you are not deficient in any of these nutrients, taking more will not give you more energy. The benefit is in correction of insufficiency, not augmentation of adequacy.
The vitamins with authorised fatigue claims — and UK deficiency data
Vitamin B12
EU-authorised claims: normal energy-yielding metabolism, normal functioning of the nervous system, reduction of tiredness and fatigue, normal psychological function, normal red blood cell formation.
B12 is found almost exclusively in animal products (meat, fish, eggs, dairy). UK dietary surveys (NDNS 2019) estimate 6% of adults under 60 have low B12 status, rising to 20%+ in adults over 65. Vegans have near-universal B12 insufficiency without supplementation. B12 deficiency causes megaloblastic anaemia, peripheral neuropathy and fatigue — symptoms that can be severe and, if prolonged, irreversible neurologically.
Effective dose: for repletion of mild deficiency, 50–150μg/day of cyanocobalamin or methylcobalamin. NHS recommends adults need approximately 1.5μg/day from food; supplement doses are higher to compensate for poor absorption at low doses. High-dose supplementation (1,000μg/day) is used for B12 deficiency when injections are not preferred — passive absorption bypasses intrinsic factor dependence at this dose.
Honest limit: if fatigue is severe or combined with neurological symptoms (numbness, tingling, balance problems), B12 deficiency requires a blood test and GP assessment — not self-supplementation. Oral supplementation at standard doses may not correct deficiency in people with intrinsic factor deficiency (pernicious anaemia) or significant malabsorption.
Folate (vitamin B9)
EU-authorised claims: reduction of tiredness and fatigue, normal blood formation, normal psychological function.
Folate works with B12 in DNA synthesis and red blood cell production. Deficiency causes megaloblastic anaemia with fatigue as a primary symptom. UK dietary surveys show folate intakes are below recommendations in a significant proportion of women of childbearing age. NHS recommends 400μg/day folic acid for women trying to conceive and in the first 12 weeks of pregnancy.
Effective dose: 200μg/day for general maintenance (the EU NRV); 400μg/day for pregnancy prevention of neural tube defects. Note: some people with MTHFR gene variants convert folic acid less efficiently — methylfolate (5-MTHF) is the active form that bypasses this conversion step.
Vitamin B6 (pyridoxine)
EU-authorised claims: normal energy-yielding metabolism, reduction of tiredness and fatigue, normal psychological function, normal functioning of the nervous system, normal cysteine synthesis.
B6 is involved in over 100 enzyme reactions, primarily in amino acid metabolism and neurotransmitter synthesis (serotonin, dopamine, GABA). UK deficiency is uncommon in mixed diets but can occur with alcohol misuse, poor diet or certain medications (isoniazid, some oral contraceptives).
Important safety note: high-dose B6 supplementation (above 10–50mg/day long term) is associated with peripheral neuropathy. The EU tolerable upper intake level is 25mg/day for adults. Avoid supplements providing very high B6 doses marketed for PMS or energy without clinical reason. The MHRA updated its guidance on high-dose B6 in 2023, requiring warning labels on products above 10mg/day.
Riboflavin (B2), Niacin (B3), Pantothenic acid (B5)
All three carry EU-authorised claims for normal energy-yielding metabolism and reduction of tiredness and fatigue. They function as precursors to FAD, NAD+ and CoA respectively — essential coenzymes in the Krebs cycle and electron transport chain. Outright deficiency is uncommon in the UK but suboptimal status in people eating restricted or highly processed diets is plausible.
No specific trial data demonstrates fatigue improvement from supplementation in non-deficient adults — the EU claims are based on well-established biochemical function, not RCT evidence in healthy people. They are most relevant as components of a comprehensive B-complex for people with dietary gaps.
Vitamin C
EU-authorised claims: normal energy-yielding metabolism, reduction of tiredness and fatigue, protection of cells from oxidative stress, increased iron absorption.
Vitamin C's fatigue relevance is primarily through iron absorption — pairing vitamin C with non-haem iron (plant sources) increases iron absorption by 2–6-fold depending on dose. A 2020 review in Nutrients confirmed vitamin C at 100mg alongside iron-rich plant foods significantly improved non-haem iron absorption. UK adults consuming little fresh fruit and vegetables may have suboptimal vitamin C status, particularly smokers (who require approximately 35mg/day more due to increased oxidative turnover).
The most common cause of fatigue UK adults miss: iron deficiency
Iron is not a vitamin, but it is the most prevalent nutritional cause of fatigue in the UK. Iron is required for haemoglobin synthesis — without adequate iron, red blood cells carry less oxygen, causing the tiredness, breathlessness and pale skin of iron deficiency anaemia.
UK NDNS data shows iron deficiency anaemia affects approximately 25% of premenopausal women. Iron depletion (low ferritin without full anaemia) is even more prevalent. A 2019 study in the British Journal of Nutrition found ferritin below 30μg/L (suboptimal, pre-anaemic range) was associated with significantly reduced cognitive performance and fatigue in non-anaemic women.
Honest limit: iron supplementation without a confirmed deficiency via blood test is not recommended — excess iron is harmful, and iron overload (haemochromatosis) is a genetic condition affecting approximately 1 in 200 people of Northern European descent. Get ferritin and full blood count tested before supplementing iron.
Vitamin D and fatigue: what the evidence shows
Vitamin D does not carry an EU-authorised reduction-of-tiredness claim. Its EU-authorised claims cover normal bone function, normal muscle function, and normal immune system function. However, severe vitamin D deficiency (<25 nmol/L) is associated with musculoskeletal pain and fatigue — a 2014 RCT in PAIN found vitamin D supplementation significantly reduced widespread musculoskeletal pain in deficient patients.
Public Health England recommends 10μg (400 IU) vitamin D for all UK adults from October to March, when sunlight is insufficient for cutaneous synthesis at UK latitudes. UK NDNS data shows mean vitamin D intakes of 4–5μg/day — well below recommendation. If fatigue is accompanied by muscle weakness, bone pain or frequent illness, vitamin D deficiency is worth investigating via blood test.
When tiredness requires a GP, not a supplement
Supplements address nutritional causes of fatigue. They cannot address medical causes. See a GP if tiredness:
- Is new and persistent (more than 4 weeks) without obvious lifestyle explanation
- Is accompanied by breathlessness, palpitations or chest pain
- Comes with unexplained weight loss, night sweats or fever
- Is accompanied by neurological symptoms (numbness, tingling, weakness)
- Is severe enough to affect daily function or work
- Is associated with low mood, anhedonia or cognitive changes
Thyroid underactivity (hypothyroidism), coeliac disease, sleep apnoea, type 2 diabetes, depression and numerous other conditions present with fatigue — none of which will be resolved by a B-complex.
Choosing a supplement for tiredness: what to look for
- Declared doses at or above 15% NRV — below this threshold, no EU-authorised claim is valid regardless of what the label implies
- Active forms where relevant: methylcobalamin (B12), methylfolate or folinic acid (B9), pyridoxal-5-phosphate (B6) — these are the forms directly usable without conversion, relevant for people with absorption issues or MTHFR variants
- B6 below 10mg/day unless specifically advised by a healthcare professional
- Iron only if blood test has confirmed deficiency
- Halal/vegan status confirmed by capsule material (HPMC) and manufacturing certification, not just front-of-pack claims
Browse the Halal Vitamins UK collection for B-complex and energy-support supplements with declared doses and allergen statements.
Which vitamin deficiency causes the most tiredness?
In the UK, iron deficiency is the most prevalent nutritional cause of fatigue, affecting approximately 25% of premenopausal women. Among vitamins specifically, B12 deficiency is the most clinically significant cause of fatigue — it also causes neurological damage if prolonged. Vegans without B12 supplementation will develop deficiency. Folate deficiency causes a similar anaemia to B12. Vitamin D severe deficiency is associated with musculoskeletal fatigue. In practice, multiple insufficiencies often co-exist in people with restricted diets or poor absorption.
Do B vitamins give you energy?
Not directly — B vitamins do not contain calories or produce ATP themselves. They act as cofactors in the metabolic pathways that convert food into usable energy. The EU-authorised wording is "contributes to normal energy-yielding metabolism" and "reduction of tiredness and fatigue" — not "provides energy." If you are not deficient in B vitamins, supplementing more will not increase your energy. The benefit is correction of insufficiency. If your diet is varied and adequate, tiredness is unlikely to be B-vitamin-driven.
Is vitamin D good for tiredness?
Vitamin D does not have an EU-authorised claim for reduction of tiredness and fatigue. Severe deficiency (<25 nmol/L) is associated with musculoskeletal pain, weakness and fatigue — and supplementation can reduce these symptoms in deficient individuals. Public Health England recommends 10μg/day for all UK adults October to March. If you are not deficient, vitamin D supplementation is unlikely to resolve tiredness. Get a blood test to check 25-OH vitamin D levels before attributing fatigue to vitamin D deficiency.
What dose of B12 should I take for tiredness?
If you are vegan or vegetarian, 50–150μg/day of cyanocobalamin or methylcobalamin daily provides reliable B12 from supplementation. If you have confirmed B12 deficiency via blood test, higher doses (1,000μg/day oral) or GP-prescribed injections may be needed. The NHS adult RNI for B12 is only 1.5μg/day from food, but supplement doses are substantially higher because absorption efficiency from supplements is lower than from food-bound B12 and decreases at higher doses. Taking a B12 supplement is not harmful at these doses — excess is excreted in urine.
Can I take iron supplements for tiredness without a blood test?
Not recommended. Iron deficiency is the most common nutritional cause of fatigue in UK women, but supplementing iron without a blood test carries risks. Excess iron intake is harmful — iron overload causes liver damage, joint pain and cardiovascular problems. Haemochromatosis (genetic iron overload disorder) affects approximately 1 in 200 people of Northern European descent and is worsened by supplementation. Get ferritin and full blood count tested by a GP first. If ferritin is below 30μg/L or below 50μg/L with symptoms, supplementation under GP guidance is appropriate.
