Vitamins for Energy: What the NHS Says and When to See a GP

Several B vitamins and magnesium help the body release or use energy from food.^{1, 5} Most people should get all the nutrients they need by having a varied and balanced diet, although some people may need to take extra supplements.⁶ See a GP if you have been tired for a few weeks and are not sure why.⁷

Below are what each nutrient does, who is more likely to be low, what low levels can cause, what a 2021 review of vitamin B12 trials covered, what commonly causes tiredness, and when to see a GP. This is general information, not advice on your own symptoms.

What the NHS says these vitamins and minerals do

The NHS lists several B vitamins and magnesium as helping the body release or use energy from food.^{1, 5}

• Thiamin (B1), riboflavin (B2), niacin (B3) and pantothenic acid each help the body release energy from food.¹
• Vitamin B6 helps the body use and store energy from protein and carbohydrates, and helps form haemoglobin, the substance in red blood cells that carries oxygen.¹
• Vitamin B12 helps the body release energy from food, make red blood cells and use folate.¹
• Folate helps the body form healthy red blood cells.¹
• Iron is important in making red blood cells, which carry oxygen around the body.²
• Magnesium helps turn the food we eat into energy.⁵
• Vitamin C helps protect cells and keep skin, blood vessels, bones and cartilage healthy.³
• Vitamin D helps regulate calcium and phosphate, which are needed to keep bones, teeth and muscles healthy.⁴

The Great Britain nutrition and health claims register lists the wording that food labels may use: food that is at least a source of the nutrient may state "contributes to normal energy-yielding metabolism" for thiamine, riboflavin, niacin, pantothenic acid, vitamin B6, vitamin B12, vitamin C, iron and magnesium, among others.¹² The same register authorises "contributes to the reduction of tiredness and fatigue" for riboflavin, niacin, pantothenic acid, vitamin B6, vitamin B12, folate, vitamin C and iron, and "contributes to a reduction of tiredness and fatigue" for magnesium.¹²

Who is more likely to be low in a vitamin or mineral

The NHS names several groups who are more likely to be low in particular nutrients.

• Vitamin B12 is not found naturally in fruit, vegetables and grains, so vegans may not get enough.¹ Pernicious anaemia, where the immune system attacks healthy cells in the stomach and stops the body absorbing B12 from food, is the most common cause of B12 deficiency in the UK.⁹ Some medicines, including anticonvulsants and proton pump inhibitors, can affect how much B12 and folate the body absorbs.⁹
• B12 or folate deficiency is more common in older people, affecting around 1 in 10 people aged 75 or over and 1 in 20 aged 65 to 74.⁹
• Women who lose a lot of blood in heavy periods are at higher risk of iron deficiency anaemia.² Pregnancy and bleeding in the stomach or intestines are other common causes.¹⁰
• On a vegan diet that is not planned properly, calcium, iron, vitamin B12, iodine and selenium can be missed.¹¹
• The NHS advises everyone to consider a daily 10 microgram vitamin D supplement in autumn and winter, because between October and early March the body does not make enough from sunlight.⁴

Tiredness as a symptom of low levels

Tiredness and a lack of energy are among the symptoms the NHS lists for vitamin B12 deficiency, folate deficiency and iron deficiency anaemia.^{9, 10} For B12 or folate deficiency the NHS also lists pins and needles, a sore and red tongue, muscle weakness and problems with memory.⁹ For iron deficiency anaemia it lists shortness of breath, noticeable heartbeats, paler than usual skin and headaches.¹⁰

B12 and folate deficiency can often be diagnosed from your symptoms and a blood test.⁹ The NHS says it is important for B12 or folate deficiency anaemia to be diagnosed and treated as soon as possible, because some problems caused by the condition can be irreversible.⁹

What a 2021 review of vitamin B12 trials covered

A 2021 systematic review and meta-analysis pooled 16 double-blind, placebo-controlled trials of vitamin B12 supplementation in 6,276 people without overt B12 deficiency or advanced neurological disorders.¹³ The average ages in the trials ranged from 66 to 82.¹³ The supplements were vitamin B12 alone or with folic acid, with or without vitamin B6.¹³

The review looked at cognitive function, depressive symptoms and unexplained fatigue.¹³ Only one of the trials reported on unexplained fatigue, so no analysis of fatigue was possible.¹³

What commonly causes tiredness

The NHS says many cases of tiredness are due to stress, not enough sleep, poor diet and other lifestyle factors.⁸ The NHS page on tiredness and fatigue lists these common causes:⁷

• not getting enough sleep or finding it hard to get to sleep (insomnia)
• depression and life challenges such as bereavement or looking after a new baby
• hormonal changes, such as during puberty, pregnancy or the menopause
• illnesses such as glandular fever and COVID-19
• some medical treatments and medicines, such as chemotherapy

If you cannot explain why you are tired and it has been going on for a while and not getting any better, the NHS says it may be a sign of a medical condition.⁷ It gives sleep apnoea, iron deficiency anaemia, diabetes, an overactive thyroid and ME/CFS as examples.⁷

Its self-help advice includes eating regular meals and healthy snacks every 3 to 4 hours, regular exercise, going to bed and getting up at the same time every day, avoiding caffeine in the evening and cutting down on alcohol before bedtime.⁸

When to see a GP

See a GP if you have been tired for a few weeks and are not sure why, if it affects your daily life, or if you have other symptoms such as weight loss or mood changes.⁷ The NHS adds that fatigue, an overwhelming tiredness that rest and sleep do not relieve, may point to an underlying medical condition.⁸

You may need tests, such as blood tests to check for anaemia, diabetes or an overactive thyroid.⁷ For suspected iron deficiency anaemia the usual test is a full blood count, and the NHS says the same test also checks for other types of anaemia, including B12 or folate deficiency anaemia.¹⁰ The NHS advises against diagnosing yourself and says to see a GP if you are worried.⁷

If you take a supplement

The NHS gives a daily amount for each of these supplements, and advises not to take too much because this could be harmful.

• Vitamin D: 10 micrograms a day is enough for most people who choose to take a supplement, and for adults and children aged 11 to 17 the NHS says not to take more than 100 micrograms (4,000 IU) a day.⁴
• Vitamin B6: do not take more than 10mg a day in supplements unless a doctor advises it.¹
• Vitamin B12: 2mg or less a day in supplements is unlikely to cause any harm.¹
• Folic acid: 1mg or less a day is unlikely to cause any harm, and doses higher than 1mg can mask the symptoms of vitamin B12 deficiency.¹
• Iron: 17mg or less a day is unlikely to cause any harm, and the NHS says to keep taking a higher dose if a GP has advised it.²
• Vitamin C: less than 1,000mg a day is unlikely to cause any harm.³
• Magnesium: 400mg or less a day from supplements is unlikely to cause any harm.⁵

For vitamin D, the NHS says some medical conditions mean a person cannot safely take as much, and to follow a doctor's advice if given a different amount.⁴

Several of the blood test profiles at our London clinic include vitamin B12, folate and vitamin D; testing can begin with a complimentary nurse consultation, and results are delivered within 24 to 48 hours (blood testing in London).

Sources

1. B vitamins and folic acid, NHS, reviewed August 2020
2. Iron, NHS, reviewed August 2020
3. Vitamin C, NHS, reviewed August 2020
4. Vitamin D, NHS, reviewed August 2020
5. Others (magnesium), NHS, reviewed August 2020
6. Vitamins and minerals overview, NHS, reviewed August 2020
7. Tiredness and fatigue, NHS, reviewed June 2023
8. Self-help tips to fight tiredness, NHS, reviewed November 2023
9. Vitamin B12 or folate deficiency anaemia, NHS, reviewed February 2023
10. Iron deficiency anaemia, NHS, reviewed January 2024
11. The vegan diet, NHS, reviewed June 2026
12. GB nutrition and health claims register, DHSC, updated May 2026
13. Vitamin B12 supplementation, systematic review, Markun et al., Nutrients, 2021