B Vitamins Explained: What Each One Does and Who Needs Them

"B vitamins" sounds like a single nutrient, but it is actually a family of eight different vitamins, each with its own job. They are water-soluble, so the body cannot store most of them in large amounts, which means you need a regular supply from food. This guide explains what each B vitamin does, how much you need, where to find them and who might benefit from a supplement.

The eight B vitamins in brief

The B group includes thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), vitamin B6, biotin (B7), folate (B9, called folic acid in supplements) and vitamin B12. They often work together, especially in helping the body release energy from food.

Below, each vitamin is listed with the NHS daily amounts for adults and a selection of its authorised health claims from the GB Nutrition and Health Claims Register. Claims apply when a food or supplement provides at least 15% of the Nutrient Reference Value per daily portion.

Thiamin (B1)

Needs: about 1mg a day for men and 0.8mg for women. Sources: wholegrain bread, fortified breakfast cereals, peas, nuts, pork. Claims: thiamin contributes to normal energy-yielding metabolism, to the normal functioning of the nervous system and to normal psychological function.

Riboflavin (B2)

Needs: about 1.3mg a day for men and 1.1mg for women. Sources: milk, eggs, fortified cereals, mushrooms. Claims: riboflavin contributes to the reduction of tiredness and fatigue, to the maintenance of normal skin and normal vision, and to the protection of cells from oxidative stress.

Niacin (B3)

Needs: about 16.5mg a day for men and 13.2mg for women. Sources: meat, fish, wheat flour, eggs. Claims: niacin contributes to normal energy-yielding metabolism, to normal psychological function and to the reduction of tiredness and fatigue.

Pantothenic acid (B5)

Needs: no UK amount is set; it is found in most foods. Sources: chicken, beef, eggs, mushrooms, avocado, wholegrains. Claims: pantothenic acid contributes to normal mental performance and to the reduction of tiredness and fatigue.

Vitamin B6

Needs: about 1.4mg a day for men and 1.2mg for women. Sources: poultry, fish, peanuts, oats, bananas, soya beans. Claims: vitamin B6 contributes to normal protein and glycogen metabolism, to the regulation of hormonal activity and to the normal function of the immune system.

Biotin (B7)

Needs: the body only needs very small amounts, and most people get enough from food. Sources: eggs, nuts, seeds, some vegetables. Claims: biotin contributes to the maintenance of normal hair and normal skin and to normal macronutrient metabolism.

Folate (B9)

Needs: 200 micrograms of folate a day for adults. Anyone who is pregnant, trying for a baby or could get pregnant is advised to take a 400 microgram folic acid supplement daily until the 12th week of pregnancy. Sources: broccoli, Brussels sprouts, leafy greens, chickpeas, fortified cereals. Claims: folate contributes to normal blood formation, to the reduction of tiredness and fatigue and to maternal tissue growth during pregnancy.

Vitamin B12

Needs: about 1.5 micrograms a day for adults. Sources: meat, fish, eggs, dairy, and fortified foods such as some plant drinks, cereals and yeast extract. Claims: vitamin B12 contributes to normal red blood cell formation, to the normal functioning of the nervous system and to the reduction of tiredness and fatigue.

Why B vitamins matter for active people

If you train regularly, your body is turning more food into usable energy. Several B vitamins (thiamin, riboflavin, niacin, pantothenic acid, B6, biotin and B12) contribute to normal energy-yielding metabolism, which is why they are often discussed in sports nutrition. Vitamin B6 also contributes to normal protein and glycogen metabolism, which links directly to how your body uses protein and stored carbohydrate.

It is worth being clear about what that means. B vitamins do not provide energy themselves, and taking more than you need will not make you feel more energetic. They help your body use the energy in food normally. If your intake is already adequate, extra B vitamins are simply excreted.

Who might need a B-vitamin supplement?

Vegans and many vegetarians

Vitamin B12 is found naturally almost only in animal foods, so people following a vegan diet need fortified foods or a supplement. This is the single most important B-vitamin consideration in the UK. Our Vitamin B12 provides 1,000 µg of B12 per tablet in a vegan formula, and one pack lasts more than 15 months at one tablet a day.

Older adults

Absorption of vitamin B12 from food can become less efficient with age, partly because of changes in stomach acid. Some medicines can also affect B12 levels. If you are concerned, ask your GP about a blood test rather than guessing.

People planning a pregnancy

Folic acid supplementation is recommended before conception and in early pregnancy. A pregnancy-specific product is usually the best choice.

People with restricted or irregular diets

If you skip meals, eat a narrow range of foods or are in a prolonged calorie deficit, a B-complex supplement can help cover the basics while you improve your diet. Vitamin B Complex provides the full B group, including biotin and folic acid, in one tablet.

Safety: can you have too much?

Because they are water-soluble, B vitamins are generally considered low risk, but there are some important limits from the NHS:

• Vitamin B6: do not take more than 10mg a day from supplements unless advised by a doctor. Long-term high intakes have been linked to loss of feeling in the arms and legs.
• Niacin: high doses of nicotinic acid can cause skin flushing, and very high doses over a long time may affect the liver.
• Folic acid: more than 1mg a day can mask the symptoms of B12 deficiency.

Check every product you take. A multivitamin, a B complex and an "energy" supplement can easily overlap. Bright yellow urine after taking B vitamins is harmless; it is simply excess riboflavin.

Biotin supplements can also interfere with some laboratory blood tests, so tell your doctor if you take one before a blood test.

Food first: easy ways to cover your B vitamins

• Choose a fortified breakfast cereal or oats with milk (or a fortified plant drink).
• Include eggs, fish, poultry or pulses in most meals.
• Add leafy greens, broccoli or Brussels sprouts several times a week.
• Use yeast extract or nutritional yeast if you are plant-based.
• Snack on nuts and seeds.

Products mentioned in this article

Frequently asked questions

What is the best time to take B vitamins?

Many people take them with breakfast. There is no strong evidence that timing matters, so choose a time you will remember.

Do B vitamins give you energy?

B vitamins do not contain energy. Several contribute to normal energy-yielding metabolism and to the reduction of tiredness and fatigue, but extra amounts beyond your needs will not increase energy.

Should vegans take vitamin B12?

Yes. People on a vegan diet need a reliable source of vitamin B12 from fortified foods or a supplement.

Can I take a B complex and a multivitamin together?

You can, but check the combined amounts, particularly of vitamin B6, to stay within safe limits.

Why does my urine turn yellow after taking B vitamins?

This is caused by riboflavin (B2) and is harmless.

Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle.